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Bonnycastle K, Nawaz MS, Kind PC, Cousin MA. Convergent depression of activity-dependent bulk endocytosis in rodent models of autism spectrum disorder. Mol Autism 2025; 16:26. [PMID: 40241211 PMCID: PMC12004638 DOI: 10.1186/s13229-025-00660-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2024] [Accepted: 03/24/2025] [Indexed: 04/18/2025] Open
Abstract
BACKGROUND The key pathological mechanisms underlying autism spectrum disorder (ASD) remain relatively undetermined, potentially due to the heterogenous nature of the condition. Targeted studies of a series of monogenic ASDs have revealed postsynaptic dysfunction as a central conserved mechanism. Presynaptic dysfunction is emerging as an additional disease locus in neurodevelopmental disorders; however, it is unclear whether this dysfunction drives ASD or is an adaptation to the altered brain microenvironment. METHODS To differentiate between these two competing scenarios, we performed a high content analysis of key stages of the synaptic vesicle lifecycle in primary neuronal cultures derived from a series of preclinical rat models of monogenic ASD. These five independent models (Nrxn1+/-, Nlgn3-/y, Syngap+/-, Syngap+/Δ-GAP, Pten+/-) were specifically selected to have perturbations in a diverse palette of genes that were expressed either at the pre- or post-synapse. Synaptic vesicle exocytosis and cargo trafficking were triggered via two discrete trains of activity and monitored using the genetically-encoded reporter synaptophysin-pHluorin. Activity-dependent bulk endocytosis was assessed during intense neuronal activity using the fluid phase marker tetramethylrhodamine-dextran. RESULTS Both synaptic vesicle fusion events and cargo trafficking were unaffected in all models investigated under all stimulation protocols. However, a key convergent phenotype across neurons derived from all five models was revealed, a depression in activity-dependent bulk endocytosis. LIMITATIONS The study is exclusively conducted in primary cultures of hippocampal neurons; therefore, the impact on neurons from other brain regions or altered brain microcircuitry was not assessed. No molecular mechanism has been identified for this depression. CONCLUSION This suggests that depression of activity-dependent bulk endocytosis is a presynaptic homeostatic mechanism to correct for intrinsic dysfunction in ASD neurons.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Service de Génétique Médicale, Centre Hospitalier Universitaire (CHU) Sainte-Justine, Université de Montréal, Montreal, QC, Canada
| | - Mohammed Sarfaraz Nawaz
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
| | - Peter C Kind
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK.
- Simons Initiative for the Developing Brain, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK.
- Muir Maxwell Epilepsy Centre, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh, Scotland, EH8 9XD, UK.
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van der Lei MB, Kooy RF. From Discovery to Innovative Translational Approaches in 80 Years of Fragile X Syndrome Research. Biomedicines 2025; 13:805. [PMID: 40299377 PMCID: PMC12024745 DOI: 10.3390/biomedicines13040805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2025] [Revised: 03/21/2025] [Accepted: 03/25/2025] [Indexed: 04/30/2025] Open
Abstract
Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and a major genetic contributor to autism spectrum disorder. It is caused by a CGG trinucleotide repeat expansion in the FMR1 gene, resulting in gene silencing and the loss of FMRP, an RNA-binding protein essential for synaptic plasticity. This review covers over 80 years of FXS research, highlighting key milestones, clinical features, genetic and molecular mechanisms, the FXS mouse model, disrupted molecular pathways, and current therapeutic strategies. Additionally, we discuss recent advances including AI-driven combination therapies, CRISPR-based gene editing, and antisense oligonucleotides (ASOs) therapies. Despite these scientific breakthroughs, translating preclinical findings into effective clinical treatments remains challenging. Clinical trials have faced several difficulties, including patient heterogeneity, inconsistent outcome measures, and variable therapeutic responses. Standardized preclinical testing protocols and refined clinical trial designs are required to overcome these challenges. The development of FXS-specific biomarkers could also improve the precision of treatment assessments. Ultimately, future therapies will need to combine pharmacological and behavioral interventions tailored to individual needs. While significant challenges remain, ongoing research continues to offer hope for transformative breakthroughs that could significantly improve the quality of life for individuals with FXS and their families.
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Affiliation(s)
| | - R. Frank Kooy
- Center of Medical Genetics, University of Antwerp and Antwerp University Hospital, 2650 Edegem, Belgium;
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Ferraguto C, Piquemal-Lagoueillat M, Lemaire V, Moreau MM, Trazzi S, Uguagliati B, Ciani E, Bertrand SS, Louette E, Bontempi B, Pietropaolo S. Therapeutic efficacy of the BKCa channel opener chlorzoxazone in a mouse model of Fragile X syndrome. Neuropsychopharmacology 2024; 49:2032-2041. [PMID: 39223257 PMCID: PMC11480417 DOI: 10.1038/s41386-024-01956-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 06/30/2024] [Accepted: 07/23/2024] [Indexed: 09/04/2024]
Abstract
Fragile X syndrome (FXS) is an X-linked neurodevelopmental disorder characterized by several behavioral abnormalities, including hyperactivity, anxiety, sensory hyper-responsiveness, and autistic-like symptoms such as social deficits. Despite considerable efforts, effective pharmacological treatments are still lacking, prompting the need for exploring the therapeutic value of existing drugs beyond their original approved use. One such repurposed drug is chlorzoxazone which is classified as a large-conductance calcium-dependent potassium (BKCa) channel opener. Reduced BKCa channel functionality has been reported in FXS patients, suggesting that molecules activating these channels could serve as promising treatments for this syndrome. Here, we sought to characterize the therapeutic potential of chlorzoxazone using the Fmr1-KO mouse model of FXS which recapitulates the main phenotypes of FXS, including BKCa channel alterations. Chlorzoxazone, administered either acutely or chronically, rescued hyperactivity and acoustic hyper-responsiveness as well as impaired social interactions exhibited by Fmr1-KO mice. Chlorzoxazone was more efficacious in alleviating these phenotypes than gaboxadol and metformin, two repurposed treatments for FXS that do not target BKCa channels. Systemic administration of chlorzoxazone modulated the neuronal activity-dependent gene c-fos in selected brain areas of Fmr1-KO mice, corrected aberrant hippocampal dendritic spines, and was able to rescue impaired BKCa currents recorded from hippocampal and cortical neurons of these mutants. Collectively, these findings provide further preclinical support for BKCa channels as a valuable therapeutic target for treating FXS and encourage the repurposing of chlorzoxazone for clinical applications in FXS and other related neurodevelopmental diseases.
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Affiliation(s)
| | | | - Valerie Lemaire
- Univ. Bordeaux, CNRS, EPHE, INCIA, UMR 5287, Bordeaux, France
| | - Maïté M Moreau
- Univ. Bordeaux, INSERM, Neurocentre Magendie, U1215, Bordeaux, France
| | - Stefania Trazzi
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Beatrice Uguagliati
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | - Elisabetta Ciani
- Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy
| | | | | | - Bruno Bontempi
- Univ. Bordeaux, CNRS, EPHE, INCIA, UMR 5287, Bordeaux, France
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4
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Honda T, Kurita K, Arai Y, Pandey H, Sawa A, Furukubo-Tokunaga K. FMR1 genetically interacts with DISC1 to regulate glutamatergic synaptogenesis. SCHIZOPHRENIA (HEIDELBERG, GERMANY) 2024; 10:112. [PMID: 39604386 PMCID: PMC11603133 DOI: 10.1038/s41537-024-00532-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2024] [Accepted: 10/31/2024] [Indexed: 11/29/2024]
Abstract
Synaptic development and functions have been hypothesized as crucial mechanisms of diverse neuropsychiatric disorders. Studies in past years suggest that mutations in the fragile X mental retardation 1 (FMR1) are associated with diverse mental disorders including intellectual disability, autistic spectrum disorder, and schizophrenia. In this study, we have examined genetical interactions between a select set of risk factor genes using fruit flies to find that dfmr1, the Drosophila homolog of the human FMR1 gene, exhibits functional interactions with DISC1 in synaptic development. We show that DISC1 overexpression in the dfmr1null heterozygous background causes synaptic alterations at the larval neuromuscular junctions that are distinct from those in the wild-type background. Loss of dfmr1 modifies the DISC1 overexpression phenotype in synaptic formation, suppressing the formation of synapse boutons. Interaction between the two genes was further supported molecularly by the results that dfmr1 mutations suppress the DISC1-mediated upregulations of the postsynaptic expression of a glutamate receptor and the expression of ELKS/CAST protein, Bruchpilot, in presynaptic motoneurons. Moreover, DISC1 overexpression in the dfmr1null heterozygous background causes downregulation of a MAP1 family protein, Futsch. These results thus suggest an intriguing converging mechanism controlled by FMR1 and DISC1 in the developing glutamatergic synapses.
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Affiliation(s)
- Takato Honda
- The Picower Institute for Learning and Memory, Department of Brain and Cognitive Sciences, Massachusettes Institute of Technology (MIT), Cambridge, MA, USA.
- Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Department of Anesthesia, Critical Care, and Pain Medicine, Massachusettes General Hospital, Harvard Medical School, Boston, MA, USA.
- Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan.
| | - Kazuki Kurita
- Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yuko Arai
- Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Himani Pandey
- Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
- Department of Biotechnology, Mahatma Gandhi Central University, Motihari, Bihar, India
| | - Akira Sawa
- Departments of Psychiatry, Neuroscience, Mental Health, Pharmacology, Biomedical Engineering and Genetic Medicine, Johns Hopkins University School of Medicine and Bloomberg School of Public Health, Johns Hopkins Medicine, Baltimore, MD, USA
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5
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Sun F, Wang H, Wu J, Quraishi IH, Zhang Y, Pedram M, Gao B, Jonas EA, Nguyen V, Wu S, Mabrouk OS, Jafar-nejad P, Kaczmarek LK. Molecular Profiling of Mouse Models of Loss or Gain of Function of the KCNT1 (Slack) Potassium Channel and Antisense Oligonucleotide Treatment. Biomolecules 2024; 14:1397. [PMID: 39595574 PMCID: PMC11591899 DOI: 10.3390/biom14111397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2024] [Revised: 10/20/2024] [Accepted: 10/29/2024] [Indexed: 11/28/2024] Open
Abstract
The potassium sodium-activated channel subtype T member 1 (KCNT1) gene encodes the Slack channel KNa1.1, which is expressed in neurons throughout the brain. Gain-of-function variants in KCNT1 are associated with a spectrum of epilepsy syndromes, and mice carrying those variants exhibit a robust phenotype similar to that observed in patients. Kcnt1 knockout (KO) mice, however, have a normal lifespan without any epileptic phenotype. To understand the molecular differences between these two models, we conducted a comprehensive proteomic analysis of the cerebral cortices of Kcnt1 KO and Kcnt1R455H/+ mice, an animal model bearing a cytoplasmic C-terminal mutation homologous to a human R474H variant that results in EIMFS. The greatest change observed in Kcnt1 KO mice compared to the wild-type mice was the increased expression of multiple proteins of the inner mitochondrial membrane. Electron microscopy studies of cortical mitochondria from Kcnt1 KO mice further confirmed a significant increase in the density of mitochondrial cristae compared to that in wild-type mice. Kcnt1 reduction by a murine-specific Kcnt1 antisense oligonucleotide (ASO) in Kcnt1R455H/+ mice partially corrected the proteomic dysregulations in the disease model. The results support the hypothesis that ASO-mediated KCNT1 reduction could be therapeutically useful in the treatment of KCNT1 epilepsies.
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Affiliation(s)
- Fangxu Sun
- Biogen Inc., Cambridge, MA 02142, USA (O.S.M.)
| | - Huafeng Wang
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Jing Wu
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Imran H. Quraishi
- Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Yalan Zhang
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Maysam Pedram
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Benbo Gao
- Biogen Inc., Cambridge, MA 02142, USA (O.S.M.)
| | - Elizabeth A. Jonas
- Department of Internal Medicine, Yale School of Medicine, New Haven, CT 06520, USA
| | - Viet Nguyen
- Biogen Inc., Cambridge, MA 02142, USA (O.S.M.)
| | - Sijia Wu
- Biogen Inc., Cambridge, MA 02142, USA (O.S.M.)
| | | | | | - Leonard K. Kaczmarek
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA
- Department of Cellular Molecular Physiology, Yale School of Medicine, New Haven, CT 06520, USA
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6
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D'Antoni S, Spatuzza M, Bonaccorso CM, Catania MV. Role of fragile X messenger ribonucleoprotein 1 in the pathophysiology of brain disorders: a glia perspective. Neurosci Biobehav Rev 2024; 162:105731. [PMID: 38763180 DOI: 10.1016/j.neubiorev.2024.105731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/14/2024] [Accepted: 05/15/2024] [Indexed: 05/21/2024]
Abstract
Fragile X messenger ribonucleoprotein 1 (FMRP) is a widely expressed RNA binding protein involved in several steps of mRNA metabolism. Mutations in the FMR1 gene encoding FMRP are responsible for fragile X syndrome (FXS), a leading genetic cause of intellectual disability and autism spectrum disorder, and fragile X-associated tremor-ataxia syndrome (FXTAS), a neurodegenerative disorder in aging men. Although FMRP is mainly expressed in neurons, it is also present in glial cells and its deficiency or altered expression can affect functions of glial cells with implications for the pathophysiology of brain disorders. The present review focuses on recent advances on the role of glial subtypes, astrocytes, oligodendrocytes and microglia, in the pathophysiology of FXS and FXTAS, and describes how the absence or reduced expression of FMRP in these cells can impact on glial and neuronal functions. We will also briefly address the role of FMRP in radial glial cells and its effects on neural development, and gliomas and will speculate on the role of glial FMRP in other brain disorders.
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Affiliation(s)
- S D'Antoni
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy
| | - M Spatuzza
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy
| | - C M Bonaccorso
- Oasi Research Institute - IRCCS, via Conte Ruggero 73, Troina 94018, Italy
| | - M V Catania
- Institute for Biomedical Research and Innovation (IRIB), National Research Council (CNR), Via Paolo Gaifami 18, Catania 95126, Italy.
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Catalano F, Santorelli D, Astegno A, Favretto F, D'Abramo M, Del Giudice A, De Sciscio ML, Troilo F, Giardina G, Di Matteo A, Travaglini-Allocatelli C. Conformational and dynamic properties of the KH1 domain of FMRP and its fragile X syndrome linked G266E variant. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2024; 1872:141019. [PMID: 38641086 DOI: 10.1016/j.bbapap.2024.141019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/26/2024] [Accepted: 04/14/2024] [Indexed: 04/21/2024]
Abstract
The Fragile X messenger ribonucleoprotein (FMRP) is a multi-domain protein involved in interactions with various macromolecules, including proteins and coding/non-coding RNAs. The three KH domains (KH0, KH1 and KH2) within FMRP are recognized for their roles in mRNA binding. In the context of Fragile X syndrome (FXS), over-and-above CGG triplet repeats expansion, three specific point mutations have been identified, each affecting one of the three KH domains (R138QKH0, G266EKH1, and I304NKH2) resulting in the expression of non-functional FMRP. This study aims to elucidate the molecular mechanism underlying the loss of function associated with the G266EKH1 pathological variant. We investigate the conformational and dynamic properties of the isolated KH1 domain and the two KH1 site-directed mutants G266EKH1 and G266AKH1. Employing a combined in vitro and in silico approach, we reveal that the G266EKH1 variant lacks the characteristic features of a folded domain. This observation provides an explanation for functional impairment observed in FMRP carrying the G266E mutation within the KH1 domain, as it renders the domain unable to fold properly. Molecular Dynamics simulations suggest a pivotal role for residue 266 in regulating the structural stability of the KH domains, primarily through stabilizing the α-helices of the domain. Overall, these findings enhance our comprehension of the molecular basis for the dysfunction associated with the G266EKH1 variant in FMRP.
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Affiliation(s)
- Flavia Catalano
- Department of Biochemical Sciences, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Daniele Santorelli
- Department of Biochemical Sciences, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Alessandra Astegno
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, Verona 37134, Italy
| | - Filippo Favretto
- Department of Biotechnology, University of Verona, Strada Le Grazie 15, Verona 37134, Italy
| | - Marco D'Abramo
- Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Alessandra Del Giudice
- Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Maria Laura De Sciscio
- Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Francesca Troilo
- CNR Institute of Molecular Biology and Pathology, P.le Aldo Moro 5, Rome 00185, Italy
| | - Giorgio Giardina
- Department of Biochemical Sciences, Sapienza University of Rome, P.le Aldo Moro 5, Rome 00185, Italy
| | - Adele Di Matteo
- CNR Institute of Molecular Biology and Pathology, P.le Aldo Moro 5, Rome 00185, Italy.
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Echeverría F, Gonzalez-Sanabria N, Alvarado-Sanchez R, Fernández M, Castillo K, Latorre R. Large conductance voltage-and calcium-activated K + (BK) channel in health and disease. Front Pharmacol 2024; 15:1373507. [PMID: 38584598 PMCID: PMC10995336 DOI: 10.3389/fphar.2024.1373507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/12/2024] [Indexed: 04/09/2024] Open
Abstract
Large Conductance Voltage- and Calcium-activated K+ (BK) channels are transmembrane pore-forming proteins that regulate cell excitability and are also expressed in non-excitable cells. They play a role in regulating vascular tone, neuronal excitability, neurotransmitter release, and muscle contraction. Dysfunction of the BK channel can lead to arterial hypertension, hearing disorders, epilepsy, and ataxia. Here, we provide an overview of BK channel functioning and the implications of its abnormal functioning in various diseases. Understanding the function of BK channels is crucial for comprehending the mechanisms involved in regulating vital physiological processes, both in normal and pathological conditions, controlled by BK. This understanding may lead to the development of therapeutic interventions to address BK channelopathies.
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Affiliation(s)
- Felipe Echeverría
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Naileth Gonzalez-Sanabria
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Rosangelina Alvarado-Sanchez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Miguel Fernández
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
- Centro de Investigación de Estudios Avanzados del Maule, Vicerrectoría de Investigación y Postgrado, Universidad Católica del Maule, Talca, Chile
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencia, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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Malone TJ, Wu J, Zhang Y, Licznerski P, Chen R, Nahiyan S, Pedram M, Jonas EA, Kaczmarek LK. Neuronal potassium channel activity triggers initiation of mRNA translation through binding of translation regulators. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.07.579306. [PMID: 38370631 PMCID: PMC10871293 DOI: 10.1101/2024.02.07.579306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Neuronal activity stimulates mRNA translation crucial for learning and development. While FMRP (Fragile X Mental Retardation Protein) and CYFIP1 (Cytoplasmic FMR1 Interacting Protein 1) regulate translation, the mechanism linking translation to neuronal activity is not understood. We now find that translation is stimulated when FMRP and CYFIP1 translocate to the potassium channel Slack (KCNT1, Slo2.2). When Slack is activated, both factors are released from eIF4E (Eukaryotic Initiation Factor 4E), where they normally inhibit translation initiation. A constitutively active Slack mutation and pharmacological stimulation of the wild-type channel both increase binding of FMRP and CYFIP1 to the channel, enhancing the translation of a reporter for β-actin mRNA in cell lines and the synthesis of β-actin in neuronal dendrites. Slack activity-dependent translation is abolished when both FMRP and CYFIP1 expression are suppressed. The effects of Slack mutations on activity-dependent translation may explain the severe intellectual disability produced by these mutations in humans. HIGHLIGHTS Activation of Slack channels triggers translocation of the FMRP/CYFIP1 complexSlack channel activation regulates translation initiation of a β-actin reporter constructA Slack gain-of-function mutation increases translation of β-actin reporter construct and endogenous cortical β-actinFMRP and CYFIP1 are required for Slack activity-dependent translation. IN BRIEF Malone et al . show that the activation of Slack channels triggers translocation of the FMRP/CYFIP1 complex from the translation initiation factor eIF4E to the channel. This translocation releases eIF4E and stimulates mRNA translation of a reporter for β-actin and cortical β-actin mRNA, elucidating the mechanism that connects neuronal activity with translational regulation.
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Mitchell ME, Cook LC, Shiers S, Tavares-Ferreira D, Akopian AN, Dussor G, Price TJ. Characterization of Fragile X Mental Retardation Protein expression in human nociceptors and their axonal projections to the spinal dorsal horn. J Comp Neurol 2023; 531:814-835. [PMID: 36808110 PMCID: PMC10038933 DOI: 10.1002/cne.25463] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 12/20/2022] [Accepted: 01/27/2023] [Indexed: 02/23/2023]
Abstract
Fragile X Mental Retardation Protein (FMRP) regulates activity-dependent RNA localization and local translation to modulate synaptic plasticity throughout the central nervous system. Mutations in the FMR1 gene that hinder or ablate FMRP function cause Fragile X Syndrome (FXS), a disorder associated with sensory processing dysfunction. FXS premutations are associated with increased FMRP expression and neurological impairments including sex dimorphic presentations of chronic pain. In mice, FMRP ablation causes dysregulated dorsal root ganglion (DRG) neuron excitability and synaptic vesicle exocytosis, spinal circuit activity, and decreased translation-dependent nociceptive sensitization. Activity-dependent, local translation is a key mechanism for enhancing primary nociceptor excitability that promotes pain in animals and humans. These works indicate that FMRP likely regulates nociception and pain at the level of the primary nociceptor or spinal cord. Therefore, we sought to better understand FMRP expression in the human DRG and spinal cord using immunostaining in organ donor tissues. We find that FMRP is highly expressed in DRG and spinal neuron subsets with substantia gelatinosa exhibiting the most abundant immunoreactivity in spinal synaptic fields. Here, it is expressed in nociceptor axons. FMRP puncta colocalized with Nav1.7 and TRPV1 receptor signals suggesting a pool of axoplasmic FMRP localizes to plasma membrane-associated loci in these branches. Interestingly, FMRP puncta exhibited notable colocalization with calcitonin gene-related peptide (CGRP) immunoreactivity selectively in female spinal cord. Our results support a regulatory role for FMRP in human nociceptor axons of the dorsal horn and implicate it in the sex dimorphic actions of CGRP signaling in nociceptive sensitization and chronic pain.
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Affiliation(s)
- Molly E Mitchell
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Lauren C Cook
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Stephanie Shiers
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Diana Tavares-Ferreira
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Armen N Akopian
- Department of Endodontics, UT Health San Antonio, San Antonio, Texas, USA
| | - Gregory Dussor
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Theodore J Price
- Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
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Geng J, Khaket TP, Pan J, Li W, Zhang Y, Ping Y, Cobos Sillero MI, Lu B. Deregulation of ER-mitochondria contact formation and mitochondrial calcium homeostasis mediated by VDAC in fragile X syndrome. Dev Cell 2023; 58:597-615.e10. [PMID: 37040696 PMCID: PMC10113018 DOI: 10.1016/j.devcel.2023.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 07/31/2022] [Accepted: 03/06/2023] [Indexed: 04/13/2023]
Abstract
Loss of fragile X messenger ribonucleoprotein (FMRP) causes fragile X syndrome (FXS), the most prevalent form of inherited intellectual disability. Here, we show that FMRP interacts with the voltage-dependent anion channel (VDAC) to regulate the formation and function of endoplasmic reticulum (ER)-mitochondria contact sites (ERMCSs), structures that are critical for mitochondrial calcium (mito-Ca2+) homeostasis. FMRP-deficient cells feature excessive ERMCS formation and ER-to-mitochondria Ca2+ transfer. Genetic and pharmacological inhibition of VDAC or other ERMCS components restored synaptic structure, function, and plasticity and rescued locomotion and cognitive deficits of the Drosophila dFmr1 mutant. Expressing FMRP C-terminal domain (FMRP-C), which confers FMRP-VDAC interaction, rescued the ERMCS formation and mito-Ca2+ homeostasis defects in FXS patient iPSC-derived neurons and locomotion and cognitive deficits in Fmr1 knockout mice. These results identify altered ERMCS formation and mito-Ca2+ homeostasis as contributors to FXS and offer potential therapeutic targets.
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Affiliation(s)
- Ji Geng
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Tejinder Pal Khaket
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Jie Pan
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Wen Li
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Yan Zhang
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Key Laboratory of Psychotic Disorders (No. 13dz2260500), Shanghai Mental Health Center, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
| | - Yong Ping
- Bio-X Institutes, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Key Laboratory of Psychotic Disorders (No. 13dz2260500), Shanghai Mental Health Center, School of Medicine, Shanghai Jiao Tong University, Shanghai 200030, China
| | | | - Bingwei Lu
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305, USA.
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12
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Wang X, Sela-Donenfeld D, Wang Y. Axonal and presynaptic FMRP: Localization, signal, and functional implications. Hear Res 2023; 430:108720. [PMID: 36809742 PMCID: PMC9998378 DOI: 10.1016/j.heares.2023.108720] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 01/22/2023] [Accepted: 02/09/2023] [Indexed: 02/12/2023]
Abstract
Fragile X mental retardation protein (FMRP) binds a selected set of mRNAs and proteins to guide neural circuit assembly and regulate synaptic plasticity. Loss of FMRP is responsible for Fragile X syndrome, a neuropsychiatric disorder characterized with auditory processing problems and social difficulty. FMRP actions in synaptic formation, maturation, and plasticity are site-specific among the four compartments of a synapse: presynaptic and postsynaptic neurons, astrocytes, and extracellular matrix. This review summarizes advancements in understanding FMRP localization, signals, and functional roles in axons and presynaptic terminals.
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Affiliation(s)
- Xiaoyu Wang
- Division of Histology & Embryology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Medical College, Jinan University, Guangzhou 510632, China
| | - Dalit Sela-Donenfeld
- Koret School of Veterinary Medicine, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Yuan Wang
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University College of Medicine, Tallahassee, FL 32306, USA.
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13
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Potassium channelopathies associated with epilepsy-related syndromes and directions for therapeutic intervention. Biochem Pharmacol 2023; 208:115413. [PMID: 36646291 DOI: 10.1016/j.bcp.2023.115413] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 01/06/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023]
Abstract
A number of mutations to members of several CNS potassium (K) channel families have been identified which result in rare forms of neonatal onset epilepsy, or syndromes of which one prominent characteristic is a form of epilepsy. Benign Familial Neonatal Convulsions or Seizures (BFNC or BFNS), also referred to as Self-Limited Familial Neonatal Epilepsy (SeLNE), results from mutations in 2 members of the KV7 family (KCNQ) of K channels; while generally self-resolving by about 15 weeks of age, these mutations significantly increase the probability of generalized seizure disorders in the adult, in some cases they result in more severe developmental syndromes. Epilepsy of Infancy with Migrating Focal Seizures (EIMSF), or Migrating Partial Seizures of Infancy (MMPSI), is a rare severe form of epilepsy linked primarily to gain of function mutations in a member of the sodium-dependent K channel family, KCNT1 or SLACK. Finally, KCNMA1 channelopathies, including Liang-Wang syndrome (LIWAS), are rare combinations of neurological symptoms including seizure, movement abnormalities, delayed development and intellectual disabilities, with Liang-Wang syndrome an extremely serious polymalformative syndrome with a number of neurological sequelae including epilepsy. These are caused by mutations in the pore-forming subunit of the large-conductance calcium-activated K channel (BK channel) KCNMA1. The identification of these rare but significant channelopathies has resulted in a resurgence of interest in their treatment by direct pharmacological or genetic modulation. We will briefly review the genetics, biophysics and pharmacology of these K channels, their linkage with the 3 syndromes described above, and efforts to more effectively target these syndromes.
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14
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Abstract
The fragile X-related disorders are an important group of hereditary disorders that are caused by expanded CGG repeats in the 5' untranslated region of the FMR1 gene or by mutations in the coding sequence of this gene. Two categories of pathological CGG repeats are associated with these disorders, full mutation alleles and shorter premutation alleles. Individuals with full mutation alleles develop fragile X syndrome, which causes autism and intellectual disability, whereas those with premutation alleles, which have shorter CGG expansions, can develop fragile X-associated tremor/ataxia syndrome, a progressive neurodegenerative disease. Thus, fragile X-related disorders can manifest as neurodegenerative or neurodevelopmental disorders, depending on the size of the repeat expansion. Here, we review mouse models of fragile X-related disorders and discuss how they have informed our understanding of neurodegenerative and neurodevelopmental disorders. We also assess the translational value of these models for developing rational targeted therapies for intellectual disability and autism disorders.
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Affiliation(s)
- Rob Willemsen
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
| | - R. Frank Kooy
- Department of Clinical Genetics, Erasmus University Medical Center, 3015 CN Rotterdam, the Netherlands. Department of Medical Genetics, University of Antwerp, 2000 Antwerp, Belgium
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15
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Folding Mechanism and Aggregation Propensity of the KH0 Domain of FMRP and Its R138Q Pathological Variant. Int J Mol Sci 2022; 23:ijms232012178. [PMID: 36293035 PMCID: PMC9603430 DOI: 10.3390/ijms232012178] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 11/16/2022] Open
Abstract
The K-homology (KH) domains are small, structurally conserved domains found in proteins of different origins characterized by a central conserved βααβ “core” and a GxxG motif in the loop between the two helices of the KH core. In the eukaryotic KHI type, additional αβ elements decorate the “core” at the C-terminus. Proteins containing KH domains perform different functions and several diseases have been associated with mutations in these domains, including those in the fragile X mental retardation protein (FMRP). FMRP is an RNA-binding protein crucial for the control of RNA metabolism whose lack or mutations lead to fragile X syndrome (FXS). Among missense mutations, the R138Q substitution is in the KH0 degenerated domain lacking the classical GxxG motif. By combining equilibrium and kinetic experiments, we present a characterization of the folding mechanism of the KH0 domain from the FMRP wild-type and of the R138Q variant showing that in both cases the folding mechanism implies the accumulation of an on-pathway transient intermediate. Moreover, by exploiting a battery of biophysical techniques, we show that the KH0 domain has the propensity to form amyloid-like aggregates in mild conditions in vitro and that the R138Q mutation leads to a general destabilization of the protein and to an increased fibrillogenesis propensity.
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16
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Deng PY, Kumar A, Cavalli V, Klyachko VA. FMRP regulates GABA A receptor channel activity to control signal integration in hippocampal granule cells. Cell Rep 2022; 39:110820. [PMID: 35584668 DOI: 10.1016/j.celrep.2022.110820] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 03/11/2022] [Accepted: 04/21/2022] [Indexed: 11/29/2022] Open
Abstract
Fragile X syndrome, the most common inherited form of intellectual disability, is caused by loss of fragile X mental retardation protein (FMRP). GABAergic system dysfunction is one of the hallmarks of FXS, yet the underlying mechanisms remain poorly understood. Here, we report that FMRP interacts with GABAA receptor (GABAAR) and modulates its single-channel activity. Specifically, FMRP regulates spontaneous GABAAR opening through modulating its single-channel conductance and open probability in dentate granule cells. FMRP loss reduces spontaneous GABAAR activity underlying tonic inhibition, while N-terminal FMRP fragment (aa 1-297) is sufficient to rapidly normalize tonic inhibition in Fmr1 knockout (KO) granule cells. FMRP-GABAAR interaction is supported by co-immunoprecipitation of FMRP with at least one GABAAR subunit, the α5. Functionally, FMRP-GABAAR interaction ensures accuracy of coincidence detection of granule cells, which is markedly reduced in Fmr1 KOs. Our study reveals a mechanism underlying FMRP regulation of the GABAergic system and information processing in the hippocampus.
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Affiliation(s)
- Pan-Yue Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Ajeet Kumar
- Department of Neuroscience, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Valeria Cavalli
- Department of Neuroscience, Washington University School of Medicine, St Louis, MO 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA; Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Vitaly A Klyachko
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, MO 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA.
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17
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Perche O, Lesne F, Patat A, Raab S, Twyman R, Ring RH, Briault S. Large-conductance calcium-activated potassium channel haploinsufficiency leads to sensory deficits in the visual system: a case report. J Med Case Rep 2022; 16:180. [PMID: 35509069 PMCID: PMC9069818 DOI: 10.1186/s13256-022-03387-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Accepted: 03/27/2022] [Indexed: 12/11/2022] Open
Abstract
Background Mutations in the genes encoding the large-conductance calcium-activated potassium channel, especially KCNMA1 encoding its α-subunit, have been linked to several neurological features, including intellectual disability or autism. Associated with neurodevelopmental phenotypes, sensory function disturbances are considered to be important clinical features contributing to a variety of behavioral impairments. Large-conductance calcium-activated potassium channels are important in regulating neurotransmission in sensory circuits, including visual pathways. Deficits in visual function can contribute substantially to poor quality of life, while therapeutic approaches aimed at addressing such visual deficits represent opportunities to improve neurocognitive and neurobehavioral outcomes. Case presentation We describe the case of a 25-year-old Caucasian male with autism spectrum disorder and severe intellectual disability presenting large-conductance calcium-activated potassium channel haploinsufficiency due to a de novo balanced translocation (46, XY, t [9; 10] [q23;q22]) disrupting the KCNMA1 gene. The visual processing pathway of the subject was evaluated using both electroretinography and visual contrast sensitivity, indicating that both retinal bipolar cell function and contrast discrimination performance were reduced by approximately 60% compared with normative control values. These findings imply a direct link between KCNMA1 gene disruption and visual dysfunction in humans. In addition, the subject reported photophobia but did not exhibit strabismus, nystagmus, or other visual findings on physical examination. Conclusions This case study of a subject with large-conductance calcium-activated potassium channel haploinsufficiency and photophobia revealed a visual pathway deficit at least at the retinal level, with diminished retinal light capture likely due to bipolar cell dysfunction and an associated loss of contrast sensitivity. The data suggest that large-conductance calcium-activated potassium channels play an important role in the normal functioning of the visual pathway in humans, and that their disruption may play a role in visual and other sensory system symptomatology in large-conductance calcium-activated potassium channelopathies or conditions where disruption of large-conductance calcium-activated potassium channel function is a relevant feature of the pathophysiology, such as fragile X syndrome. This work suggests that the combined use of physiological (electroretinography) and functional (contrast sensitivity) approaches may have utility as a biomarker strategy for identifying and characterizing visual processing deficits in individuals with large-conductance calcium-activated potassium channelopathy. Trial registration ID-RCB number 2019-A01015-52, registered 17/05/2019.
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Affiliation(s)
- Olivier Perche
- Genetic Department, Centre Hospitalier Régional d'Orléans, Orléans, France.,UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique (CNRS), Orléans, France.,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France.,Kaerus Bioscience Ltd, London, EC1Y 4YX, UK
| | | | | | | | | | - Robert H Ring
- Kaerus Bioscience Ltd, London, EC1Y 4YX, UK.,Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, USA
| | - Sylvain Briault
- Genetic Department, Centre Hospitalier Régional d'Orléans, Orléans, France. .,UMR7355, Immunologie et Neurogénétique Expérimentales et Moléculaires (INEM), Centre National de la Recherche Scientifique (CNRS), Orléans, France. .,Experimental and Molecular Immunology and Neurogenetics, University of Orléans, Orléans, France. .,Kaerus Bioscience Ltd, London, EC1Y 4YX, UK.
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18
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Hurley MJ, Deacon RMJ, Chan AWE, Baker D, Selwood DL, Cogram P. Reversal of behavioural phenotype by the cannabinoid-like compound VSN16R in fragile X syndrome mice. Brain 2022; 145:76-82. [PMID: 34196695 PMCID: PMC8967084 DOI: 10.1093/brain/awab246] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 04/27/2021] [Accepted: 06/06/2021] [Indexed: 11/14/2022] Open
Abstract
Fragile X syndrome is the most common inherited intellectual disability and mono-genetic cause of autism spectrum disorder. It is a neurodevelopmental condition occurring due to a CGG trinucleotide expansion in the FMR1 gene. Polymorphisms and variants in large-conductance calcium-activated potassium channels are increasingly linked to intellectual disability and loss of FMR protein causes reduced large-conductance calcium-activated potassium channel activity leading to abnormalities in synapse function. Using the cannabinoid-like large-conductance calcium-activated potassium channel activator VSN16R we rescued behavioural deficits such as repetitive behaviour, hippocampal dependent tests of daily living, hyperactivity and memory in a mouse model of fragile X syndrome. VSN16R has been shown to be safe in a phase 1 study in healthy volunteers and in a phase 2 study in patients with multiple sclerosis with high oral bioavailability and no serious adverse effects reported. VSN16R could therefore be directly utilized in a fragile X syndrome clinical study. Moreover, VSN16R showed no evidence of tolerance, which strongly suggests that chronic VSN16R may have great therapeutic value for fragile X syndrome and autism spectrum disorder. This study provides new insight into the pathophysiology of fragile X syndrome and identifies a new pathway for drug intervention for this debilitating disorder.
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Affiliation(s)
- Michael J Hurley
- Neuroimmunology, Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton SO16 6YD, UK
- Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London NW3 2PF, UK
| | - Robert M J Deacon
- Biomedicine Division, Fraunhofer Research Institute, Center for System Biotechnology, Santiago, Chile
| | - A W Edith Chan
- Drug Discovery, UCL Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
| | - David Baker
- Centre for Neuroscience and Trauma, Blizard Institute, Queen Mary University of London, London E1 2AT, UK
| | - David L Selwood
- Drug Discovery, UCL Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
| | - Patricia Cogram
- Biomedicine Division, Fraunhofer Research Institute, Center for System Biotechnology, Santiago, Chile
- Department of Ecological Sciences, Institute of Ecology and Biodiversity, Faculty of Sciences, Universidad de Chile, Santiago, Chile
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19
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Mangano GD, Fontana A, Salpietro V, Antona V, Mangano GR, Nardello R. Recurrent missense variant in the nuclear export signal of FMR1 associated with FXS-like phenotype including intellectual disability, ASD, facial abnormalities. Eur J Med Genet 2022; 65:104441. [PMID: 35091116 DOI: 10.1016/j.ejmg.2022.104441] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 01/13/2022] [Accepted: 01/22/2022] [Indexed: 11/21/2022]
Abstract
Fragile X syndrome (FXS; MIM 300624) is an X-linked genetic disorder characterized by physical abnormalities associated with intellectual disability and a wide spectrum of neurological and psychiatric impairments. FXS occurs more frequently in males, 1 in 5000 males and 1 in 8000 females accounting for 1-2% of overall intellectual disability (ID). In more than 99% of patients, FXS results from expansions of a CGG triplet repeat (>200 in male) of the FMR1 gene. In the last years an increasing number, albeit still limited, of FXS subjects carrying FMR1 mutations including deletions, splicing errors, missense, and nonsense variants was reported. Nevertheless, the studies concerning the functional consequences of mutations in the FMR1 gene are rare so far and, therefore, we do not have sufficient knowledge regarding the genotype/phenotype correlation. We report a child carrying a hemizygous missense FMR1 (NM_002024.5:c.1325G > A p.Arg442Gln) variant, maternally inherited, associated with facial abnormalities, developmental delay, and social and communication deficits assessed with formal neuropsychological tests. The study contributes to highlighting the clinical differences between the CGG triplet repeat dependent phenotype and FMR1variant dependent phenotype and it also confirms the pathogenicity of the variant being reported for the second time in the literature.
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Affiliation(s)
- Giuseppe Donato Mangano
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical, Specialities "G. D'Alessandro," University of Palermo, Palermo, Italy
| | - Antonina Fontana
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical, Specialities "G. D'Alessandro," University of Palermo, Palermo, Italy
| | - Vincenzo Salpietro
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK; Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Pediatric Neurology and Muscular Diseases Unit, IRCCS Giannina Gaslini Institute, Genoa, 16147, Italy
| | - Vincenzo Antona
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical, Specialities "G. D'Alessandro," University of Palermo, Palermo, Italy
| | - Giuseppa Renata Mangano
- Department of Psychology, Educational Sciences and Human Movement, University of Palermo, Italy
| | - Rosaria Nardello
- Department of Health Promotion, Mother and Child Care, Internal Medicine and Medical, Specialities "G. D'Alessandro," University of Palermo, Palermo, Italy.
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20
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FMRP Sustains Presynaptic Function via Control of Activity-Dependent Bulk Endocytosis. J Neurosci 2022; 42:1618-1628. [PMID: 34996816 PMCID: PMC8883869 DOI: 10.1523/jneurosci.0852-21.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 12/22/2021] [Accepted: 12/23/2021] [Indexed: 11/21/2022] Open
Abstract
Synaptic vesicle (SV) recycling is essential for the maintenance of neurotransmission, with a number of neurodevelopmental disorders linked to defects in this process. Fragile X syndrome (FXS) results from a loss of fragile X mental retardation protein (FMRP) encoded by the FMR1 gene. Hyperexcitability of neuronal circuits is a key feature of FXS, therefore we investigated whether SV recycling was affected by the absence of FMRP during increased neuronal activity. We revealed that primary neuronal cultures from male Fmr1 knock-out (KO) rats display a specific defect in activity-dependent bulk endocytosis (ADBE). ADBE is dominant during intense neuronal activity, and this defect resulted in an inability of Fmr1 KO neurons to sustain SV recycling during trains of high-frequency stimulation. Using a molecular replacement strategy, we also revealed that a human FMRP mutant that cannot bind BK channels failed to correct ADBE dysfunction in KO neurons, however this dysfunction was corrected by BK channel agonists. Therefore, FMRP performs a key role in sustaining neurotransmitter release via selective control of ADBE, suggesting intervention via this endocytosis mode may correct the hyperexcitability observed in FXS.SIGNIFICANCE STATEMENT Loss of fragile X mental retardation protein (FMRP) results in fragile X syndrome (FXS), however whether its loss has a direct role in neurotransmitter release remains a matter of debate. We demonstrate that neurons lacking FMRP display a specific defect in a mechanism that sustains neurotransmitter release during intense neuronal firing, called activity-dependent bulk endocytosis (ADBE). This discovery provides key insights into mechanisms of brain communication that occur because of loss of FMRP function. Importantly it also reveals ADBE as a potential therapeutic target to correct the circuit hyperexcitability observed in FXS.
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21
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Starke EL, Zius K, Barbee SA. FXS causing missense mutations disrupt FMRP granule formation, dynamics, and function. PLoS Genet 2022; 18:e1010084. [PMID: 35202393 PMCID: PMC8903291 DOI: 10.1371/journal.pgen.1010084] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 03/08/2022] [Accepted: 02/08/2022] [Indexed: 01/01/2023] Open
Abstract
Fragile X Syndrome (FXS) is the most prevalent cause of inherited mental deficiency and is the most common monogenetic cause of autism spectral disorder (ASD). Here, we demonstrate that disease-causing missense mutations in the conserved K homology (KH) RNA binding domains (RBDs) of FMRP cause defects in its ability to form RNA transport granules in neurons. Using molecular, genetic, and imaging approaches in the Drosophila FXS model system, we show that the KH1 and KH2 domains of FMRP regulate distinct aspects of neuronal FMRP granule formation, dynamics, and transport. Furthermore, mutations in the KH domains disrupt translational repression in cells and the localization of known FMRP target mRNAs in neurons. These results suggest that the KH domains play an essential role in neuronal FMRP granule formation and function which may be linked to the molecular pathogenesis of FXS. Fragile X Syndrome (FXS) is the most common inherited neurodevelopmental disorder in humans and single gene cause of autism. Most cases of FXS are caused by the complete loss of a single protein (called FMRP). This has made it particularly difficult to understand which of the normal functions of FMRP are disrupted in cases of FXS. Recently, advances in high-throughput sequencing technologies have led to the discovery of patients with severe FXS caused by single mutations in important regions of the FMRP protein. Using a well-characterized FXS model system, we have found that two disease-causing mutations in FMRP disrupt the formation, dynamics, and function of RNA- and protein-containing granules in neurons. These granules have been shown to be involved in the transport of mRNA cargos in axons and dendrites. Disruption of these granules is linked to defects in synaptic development and plasticity. Our results show that two regions of the FMRP protein play a critical role in the control of FMRP granules. These findings suggest the disruption of these processes may be linked to FXS pathogenesis.
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Affiliation(s)
- Emily L. Starke
- Department of Biological Sciences, University of Denver, Denver, Colorado, United States of America
| | - Keelan Zius
- Department of Biological Sciences, University of Denver, Denver, Colorado, United States of America
| | - Scott A. Barbee
- Department of Biological Sciences, University of Denver, Denver, Colorado, United States of America
- Molecular and Cellular Biophysics Program, University of Denver, Denver, Colorado, United States of America
- * E-mail:
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22
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Liu X, Kumar V, Tsai NP, Auerbach BD. Hyperexcitability and Homeostasis in Fragile X Syndrome. Front Mol Neurosci 2022; 14:805929. [PMID: 35069112 PMCID: PMC8770333 DOI: 10.3389/fnmol.2021.805929] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/14/2021] [Indexed: 01/13/2023] Open
Abstract
Fragile X Syndrome (FXS) is a leading inherited cause of autism and intellectual disability, resulting from a mutation in the FMR1 gene and subsequent loss of its protein product FMRP. Despite this simple genetic origin, FXS is a phenotypically complex disorder with a range of physical and neurocognitive disruptions. While numerous molecular and cellular pathways are affected by FMRP loss, there is growing evidence that circuit hyperexcitability may be a common convergence point that can account for many of the wide-ranging phenotypes seen in FXS. The mechanisms for hyperexcitability in FXS include alterations to excitatory synaptic function and connectivity, reduced inhibitory neuron activity, as well as changes to ion channel expression and conductance. However, understanding the impact of FMR1 mutation on circuit function is complicated by the inherent plasticity in neural circuits, which display an array of homeostatic mechanisms to maintain activity near set levels. FMRP is also an important regulator of activity-dependent plasticity in the brain, meaning that dysregulated plasticity can be both a cause and consequence of hyperexcitable networks in FXS. This makes it difficult to separate the direct effects of FMR1 mutation from the myriad and pleiotropic compensatory changes associated with it, both of which are likely to contribute to FXS pathophysiology. Here we will: (1) review evidence for hyperexcitability and homeostatic plasticity phenotypes in FXS models, focusing on similarities/differences across brain regions, cell-types, and developmental time points; (2) examine how excitability and plasticity disruptions interact with each other to ultimately contribute to circuit dysfunction in FXS; and (3) discuss how these synaptic and circuit deficits contribute to disease-relevant behavioral phenotypes like epilepsy and sensory hypersensitivity. Through this discussion of where the current field stands, we aim to introduce perspectives moving forward in FXS research.
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Affiliation(s)
- Xiaopeng Liu
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Vipendra Kumar
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Nien-Pei Tsai
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Benjamin D. Auerbach
- Deparment of Molecular & Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- Beckman Institute for Advanced Science & Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
- *Correspondence: Benjamin D. Auerbach
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23
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Bleuzé L, Triaca V, Borreca A. FMRP-Driven Neuropathology in Autistic Spectrum Disorder and Alzheimer's disease: A Losing Game. Front Mol Biosci 2021; 8:699613. [PMID: 34760921 PMCID: PMC8573832 DOI: 10.3389/fmolb.2021.699613] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/24/2021] [Indexed: 12/28/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) is an RNA binding protein (RBP) whose absence is essentially associated to Fragile X Syndrome (FXS). As an RNA Binding Protein (RBP), FMRP is able to bind and recognize different RNA structures and the control of specific mRNAs is important for neuronal synaptic plasticity. Perturbations of this pathway have been associated with the autistic spectrum. One of the FMRP partners is the APP mRNA, the main protagonist of Alzheimer’s disease (AD), thereby regulating its protein level and metabolism. Therefore FMRP is associated to two neurodevelopmental and age-related degenerative conditions, respectively FXS and AD. Although these pathologies are characterized by different features, they have been reported to share a number of common molecular and cellular players. The aim of this review is to describe the double-edged sword of FMRP in autism and AD, possibly allowing the elucidation of key shared underlying mechanisms and neuronal circuits. As an RBP, FMRP is able to regulate APP expression promoting the production of amyloid β fragments. Indeed, FXS patients show an increase of amyloid β load, typical of other neurological disorders, such as AD, Down syndrome, Parkinson’s Disease, etc. Beyond APP dysmetabolism, the two neurodegenerative conditions share molecular targets, brain circuits and related cognitive deficits. In this review, we will point out the potential common neuropathological pattern which needs to be addressed and we will hopefully contribute to clarifying the complex phenotype of these two neurorological disorders, in order to pave the way for a novel, common disease-modifying therapy.
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Affiliation(s)
- Louis Bleuzé
- University de Rennes 1, Rennes, France.,Humanitas Clinical and Research Center-IRCCS, Rozzano (Mi), Italy
| | - Viviana Triaca
- Institute of Biochemistry and Cell Biology, National Research Council (CNR-IBBC), International Campus A. Buzzati Traverso, Monterotondo, Italy
| | - Antonella Borreca
- Humanitas Clinical and Research Center-IRCCS, Rozzano (Mi), Italy.,Institute of Neuroscience-National Research Council (CNR-IN), Milan, Italy
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24
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Beyond Trinucleotide Repeat Expansion in Fragile X Syndrome: Rare Coding and Noncoding Variants in FMR1 and Associated Phenotypes. Genes (Basel) 2021; 12:genes12111669. [PMID: 34828275 PMCID: PMC8623550 DOI: 10.3390/genes12111669] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 11/17/2022] Open
Abstract
FMR1 (FMRP translational regulator 1) variants other than repeat expansion are known to cause disease phenotypes but can be overlooked if they are not accounted for in genetic testing strategies. We collected and reanalyzed the evidence for pathogenicity of FMR1 coding, noncoding, and copy number variants published to date. There is a spectrum of disease-causing FMR1 variation, with clinical and functional evidence supporting pathogenicity of five splicing, five missense, one in-frame deletion, one nonsense, and four frameshift variants. In addition, FMR1 deletions occur in both mosaic full mutation patients and as constitutional pathogenic alleles. De novo deletions arise not only from full mutation alleles but also alleles with normal-sized CGG repeats in several patients, suggesting that the CGG repeat region may be prone to genomic instability even in the absence of repeat expansion. We conclude that clinical tests for potentially FMR1-related indications such as intellectual disability should include methods capable of detecting small coding, noncoding, and copy number variants.
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25
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Cattelani C, Lesiak D, Liebscher G, Singer II, Stasyk T, Wallnöfer MH, Heberle AM, Corti C, Hess MW, Pfaller K, Kwiatkowski M, Pramstaller PP, Hicks AA, Thedieck K, Müller T, Huber LA, Eca Guimaraes de Araujo M. The SZT2 Interactome Unravels New Functions of the KICSTOR Complex. Cells 2021; 10:2711. [PMID: 34685691 PMCID: PMC8534408 DOI: 10.3390/cells10102711] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/20/2021] [Accepted: 10/05/2021] [Indexed: 12/25/2022] Open
Abstract
Seizure threshold 2 (SZT2) is a component of the KICSTOR complex which, under catabolic conditions, functions as a negative regulator in the amino acid-sensing branch of mTORC1. Mutations in this gene cause a severe neurodevelopmental and epileptic encephalopathy whose main symptoms include epilepsy, intellectual disability, and macrocephaly. As SZT2 remains one of the least characterized regulators of mTORC1, in this work we performed a systematic interactome analysis under catabolic and anabolic conditions. Besides numerous mTORC1 and AMPK signaling components, we identified clusters of proteins related to autophagy, ciliogenesis regulation, neurogenesis, and neurodegenerative processes. Moreover, analysis of SZT2 ablated cells revealed increased mTORC1 signaling activation that could be reversed by Rapamycin or Torin treatments. Strikingly, SZT2 KO cells also exhibited higher levels of autophagic components, independent of the physiological conditions tested. These results are consistent with our interactome data, in which we detected an enriched pool of selective autophagy receptors/regulators. Moreover, preliminary analyses indicated that SZT2 alters ciliogenesis. Overall, the data presented form the basis to comprehensively investigate the physiological functions of SZT2 that could explain major molecular events in the pathophysiology of developmental and epileptic encephalopathy in patients with SZT2 mutations.
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Affiliation(s)
- Cecilia Cattelani
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, 39100 Bolzano, Italy; (C.C.); (P.P.P.); (A.A.H.)
| | - Dominik Lesiak
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
| | - Gudrun Liebscher
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
| | - Isabel I. Singer
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
| | - Taras Stasyk
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
| | - Moritz H. Wallnöfer
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
| | - Alexander M. Heberle
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, 6020 Innsbruck, Austria; (A.M.H.); (M.K.); (K.T.)
- Laboratory of Pediatrics, Section Systems Medicine of Metabolism and Signaling, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
| | - Corrado Corti
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, 39100 Bolzano, Italy; (C.C.); (P.P.P.); (A.A.H.)
| | - Michael W. Hess
- Institute of Histology and Embryology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.W.H.); (K.P.)
| | - Kristian Pfaller
- Institute of Histology and Embryology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.W.H.); (K.P.)
| | - Marcel Kwiatkowski
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, 6020 Innsbruck, Austria; (A.M.H.); (M.K.); (K.T.)
| | - Peter P. Pramstaller
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, 39100 Bolzano, Italy; (C.C.); (P.P.P.); (A.A.H.)
| | - Andrew A. Hicks
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, 39100 Bolzano, Italy; (C.C.); (P.P.P.); (A.A.H.)
| | - Kathrin Thedieck
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck, University of Innsbruck, 6020 Innsbruck, Austria; (A.M.H.); (M.K.); (K.T.)
- Laboratory of Pediatrics, Section Systems Medicine of Metabolism and Signaling, University of Groningen, University Medical Center Groningen, 9700 RB Groningen, The Netherlands
- Department for Neuroscience, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26129 Oldenburg, Germany
| | - Thomas Müller
- Department of Pediatrics I, Medical University of Innsbruck, 6020 Innsbruck, Austria;
| | - Lukas A. Huber
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
- Austrian Drug Screening Institute, ADSI, 6020 Innsbruck, Austria
| | - Mariana Eca Guimaraes de Araujo
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, 6020 Innsbruck, Austria; (C.C.); (D.L.); (G.L.); (I.I.S.); (T.S.); (M.H.W.); (L.A.H.)
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26
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Kshatri A, Cerrada A, Gimeno R, Bartolomé-Martín D, Rojas P, Giraldez T. Differential regulation of BK channels by fragile X mental retardation protein. J Gen Physiol 2021; 152:151651. [PMID: 32275741 PMCID: PMC7266151 DOI: 10.1085/jgp.201912502] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 03/12/2020] [Indexed: 01/28/2023] Open
Abstract
Fragile X mental retardation protein (FMRP) is an RNA-binding protein prominently expressed in neurons. Missense mutations or complete loss of FMRP can potentially lead to fragile X syndrome, a common form of inherited intellectual disability. In addition to RNA regulation, FMRP was also proposed to modulate neuronal function by direct interaction with the large conductance Ca2+- and voltage-activated potassium channel (BK) β4 regulatory subunits (BKβ4). However, the molecular mechanisms underlying FMRP regulation of BK channels were not studied in detail. We have used electrophysiology and super-resolution stochastic optical reconstruction microscopy (STORM) to characterize the effects of FMRP on pore-forming BKα subunits, as well as the association with regulatory subunits BKβ4. Our data indicate that, in the absence of coexpressed β4, FMRP alters the steady-state properties of BKα channels by decreasing channel activation and deactivation rates. Analysis using the Horrigan-Aldrich model revealed alterations in the parameters associated with channel opening (L0) and voltage sensor activation (J0). Interestingly, FMRP also altered the biophysical properties of BKαβ4 channels favoring channel opening, although not as dramatically as BKα. STORM experiments revealed clustered multi-protein complexes, consistent with FMRP interacting not only to BKαβ4 but also to BKα. Lastly, we found that a partial loss-of-function mutation in FMRP (R138Q) counteracts many of its functional effects on BKα and BKαβ4 channels. In summary, our data show that FMRP modulates the function of both BKα and BKαβ4 channels.
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Affiliation(s)
- Aravind Kshatri
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Alejandro Cerrada
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Roger Gimeno
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - David Bartolomé-Martín
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
| | - Patricio Rojas
- Departamento de Biología, Facultad de Química y Biología, Universidad de Santiago de Chile, Santiago, Chile
| | - Teresa Giraldez
- Departamento de Ciencias Medicas Basicas-Fisiologia, Universidad de La Laguna, Tenerife, Spain.,Instituto de Tecnologías Biomedicas, Universidad de La Laguna, Tenerife, Spain
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27
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Fyke W, Velinov M. FMR1 and Autism, an Intriguing Connection Revisited. Genes (Basel) 2021; 12:genes12081218. [PMID: 34440392 PMCID: PMC8394635 DOI: 10.3390/genes12081218] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/03/2021] [Accepted: 08/04/2021] [Indexed: 12/27/2022] Open
Abstract
Autism Spectrum Disorder (ASD) represents a distinct phenotype of behavioral dysfunction that includes deficiencies in communication and stereotypic behaviors. ASD affects about 2% of the US population. It is a highly heritable spectrum of conditions with substantial genetic heterogeneity. To date, mutations in over 100 genes have been reported in association with ASD phenotypes. Fragile X syndrome (FXS) is the most common single-gene disorder associated with ASD. The gene associated with FXS, FMR1 is located on chromosome X. Accordingly, the condition has more severe manifestations in males. FXS results from the loss of function of FMR1 due to the expansion of an unstable CGG repeat located in the 5'' untranslated region of the gene. About 50% of the FXS males and 20% of the FXS females meet the Diagnostic Statistical Manual 5 (DSM-5) criteria for ASD. Among the individuals with ASD, about 3% test positive for FXS. FMRP, the protein product of FMR1, is a major gene regulator in the central nervous system. Multiple pathways regulated by FMRP are found to be dysfunctional in ASD patients who do not have FXS. Thus, FXS presents the opportunity to study cellular phenomena that may have wider applications in the management of ASD and to develop new strategies for ASD therapy.
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Affiliation(s)
- William Fyke
- SUNY Downstate Medical Center, SUNY Downstate College of Medicine, Brooklyn, NY 11203, USA;
- Graduate Program in Neural and Behavioral Science, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA
| | - Milen Velinov
- Rutgers Robert Wood Johnson Medical School, New Brunswick, NJ 08901, USA
- Child Health Institute of New Jersey, New Brunswick, NJ 08901, USA
- Correspondence:
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28
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El Khouri E, Ghoumid J, Haye D, Giuliano F, Drevillon L, Briand-Suleau A, De La Grange P, Nau V, Gaillon T, Bienvenu T, Jacquemin-Sablon H, Goossens M, Amselem S, Giurgea I. Wnt/β-catenin pathway and cell adhesion deregulation in CSDE1-related intellectual disability and autism spectrum disorders. Mol Psychiatry 2021; 26:3572-3585. [PMID: 33867523 DOI: 10.1038/s41380-021-01072-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 03/08/2021] [Accepted: 03/19/2021] [Indexed: 12/26/2022]
Abstract
Among the genetic factors playing a key role in the etiology of intellectual disabilities (IDs) and autism spectrum disorders (ASDs), several encode RNA-binding proteins (RBPs). In this study, we deciphered the molecular and cellular bases of ID-ASD in a patient followed from birth to the age of 21, in whom we identified a de novo CSDE1 (Cold Shock Domain-containing E1) nonsense variation. CSDE1 encodes an RBP that regulates multiple cellular pathways by monitoring the translation and abundance of target transcripts. Analyses performed on the patient's primary fibroblasts showed that the identified CSDE1 variation leads to haploinsufficiency. We identified through RNA-seq assays the Wnt/β-catenin signaling and cellular adhesion as two major deregulated pathways. These results were further confirmed by functional studies involving Wnt-specific luciferase and substrate adhesion assays. Additional data support a disease model involving APC Down-Regulated-1 (APCDD1) and cadherin-2 (CDH2), two components of the Wnt/β-catenin pathway, CDH2 being also pivotal for cellular adhesion. Our study, which relies on both the deep phenotyping and long-term follow-up of a patient with CSDE1 haploinsufficiency and on ex vivo studies, sheds new light on the CSDE1-dependent deregulated pathways in ID-ASD.
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Affiliation(s)
- E El Khouri
- Sorbonne Université, INSERM, Maladies génétiques d'expression pédiatrique, Département de Génétique médicale, Assistance Publique Hôpitaux de Paris, Hôpital Trousseau, Paris, France
| | - J Ghoumid
- Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France.,Service de Génétique Clinique, Hôpital Jeanne de Flandre, CHU Lille, Lille, France
| | - D Haye
- Service de Génétique Médicale Centre, Hospitalo-Universitaire de Nice, Nice, France
| | - F Giuliano
- Service de Génétique Médicale Centre, Hospitalo-Universitaire de Nice, Nice, France
| | - L Drevillon
- Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France.,CHU Caen Normandie, Caen, France
| | - A Briand-Suleau
- Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France.,Service de Génétique et Biologie Moléculaires, Hôpital Cochin, INSERM UMR1266 - Institute of Psychiatry and Neuroscience of Paris (IPNP) and University of Paris, Paris, France
| | | | - V Nau
- Sorbonne Université, INSERM, Maladies génétiques d'expression pédiatrique, Département de Génétique médicale, Assistance Publique Hôpitaux de Paris, Hôpital Trousseau, Paris, France
| | - T Gaillon
- Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France
| | - T Bienvenu
- Service de Génétique et Biologie Moléculaires, Hôpital Cochin, INSERM UMR1266 - Institute of Psychiatry and Neuroscience of Paris (IPNP) and University of Paris, Paris, France
| | - H Jacquemin-Sablon
- INSERM UMR1053 Bordeaux Research in Translational Oncology, BaRITOn, Bordeaux, France
| | - M Goossens
- Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France
| | - S Amselem
- Sorbonne Université, INSERM, Maladies génétiques d'expression pédiatrique, Département de Génétique médicale, Assistance Publique Hôpitaux de Paris, Hôpital Trousseau, Paris, France
| | - I Giurgea
- Sorbonne Université, INSERM, Maladies génétiques d'expression pédiatrique, Département de Génétique médicale, Assistance Publique Hôpitaux de Paris, Hôpital Trousseau, Paris, France. .,Département de Génétique, Groupe Hospitalier Henri Mondor, Créteil, France.
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29
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Lovelace JW, Rais M, Palacios AR, Shuai XS, Bishay S, Popa O, Pirbhoy PS, Binder DK, Nelson DL, Ethell IM, Razak KA. Deletion of Fmr1 from Forebrain Excitatory Neurons Triggers Abnormal Cellular, EEG, and Behavioral Phenotypes in the Auditory Cortex of a Mouse Model of Fragile X Syndrome. Cereb Cortex 2021; 30:969-988. [PMID: 31364704 DOI: 10.1093/cercor/bhz141] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2019] [Revised: 05/08/2019] [Accepted: 05/29/2019] [Indexed: 12/13/2022] Open
Abstract
Fragile X syndrome (FXS) is a leading genetic cause of autism with symptoms that include sensory processing deficits. In both humans with FXS and a mouse model [Fmr1 knockout (KO) mouse], electroencephalographic (EEG) recordings show enhanced resting state gamma power and reduced sound-evoked gamma synchrony. We previously showed that elevated levels of matrix metalloproteinase-9 (MMP-9) may contribute to these phenotypes by affecting perineuronal nets (PNNs) around parvalbumin (PV) interneurons in the auditory cortex of Fmr1 KO mice. However, how different cell types within local cortical circuits contribute to these deficits is not known. Here, we examined whether Fmr1 deletion in forebrain excitatory neurons affects neural oscillations, MMP-9 activity, and PV/PNN expression in the auditory cortex. We found that cortical MMP-9 gelatinase activity, mTOR/Akt phosphorylation, and resting EEG gamma power were enhanced in CreNex1/Fmr1Flox/y conditional KO (cKO) mice, whereas the density of PV/PNN cells was reduced. The CreNex1/Fmr1Flox/y cKO mice also show increased locomotor activity, but not the anxiety-like behaviors. These results indicate that fragile X mental retardation protein changes in excitatory neurons in the cortex are sufficient to elicit cellular, electrophysiological, and behavioral phenotypes in Fmr1 KO mice. More broadly, these results indicate that local cortical circuit abnormalities contribute to sensory processing deficits in autism spectrum disorders.
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Affiliation(s)
| | - Maham Rais
- Division of Biomedical Sciences, School of Medicine
| | | | | | | | - Otilia Popa
- Division of Biomedical Sciences, School of Medicine
| | | | - Devin K Binder
- Division of Biomedical Sciences, School of Medicine.,Graduate Neuroscience Program, University of California Riverside, Riverside, CA 92521,USA
| | - David L Nelson
- Molecular and Human Genetics, Baylor College of Medicine , Houston, TX 77030, USA
| | - Iryna M Ethell
- Division of Biomedical Sciences, School of Medicine.,Graduate Neuroscience Program, University of California Riverside, Riverside, CA 92521,USA
| | - Khaleel A Razak
- Department of Psychology.,Graduate Neuroscience Program, University of California Riverside, Riverside, CA 92521,USA
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30
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Abstract
Fragile X syndrome (FXS) is the most common inherited form of intellectual disability and the leading monogenic cause of autism. The condition stems from loss of fragile X mental retardation protein (FMRP), which regulates a wide range of ion channels via translational control, protein-protein interactions and second messenger pathways. Rapidly increasing evidence demonstrates that loss of FMRP leads to numerous ion channel dysfunctions (that is, channelopathies), which in turn contribute significantly to FXS pathophysiology. Consistent with this, pharmacological or genetic interventions that target dysregulated ion channels effectively restore neuronal excitability, synaptic function and behavioural phenotypes in FXS animal models. Recent studies further support a role for direct and rapid FMRP-channel interactions in regulating ion channel function. This Review lays out the current state of knowledge in the field regarding channelopathies and the pathogenesis of FXS, including promising therapeutic implications.
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31
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Prieto M, Folci A, Poupon G, Schiavi S, Buzzelli V, Pronot M, François U, Pousinha P, Lattuada N, Abelanet S, Castagnola S, Chafai M, Khayachi A, Gwizdek C, Brau F, Deval E, Francolini M, Bardoni B, Humeau Y, Trezza V, Martin S. Missense mutation of Fmr1 results in impaired AMPAR-mediated plasticity and socio-cognitive deficits in mice. Nat Commun 2021; 12:1557. [PMID: 33692361 PMCID: PMC7946954 DOI: 10.1038/s41467-021-21820-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 02/16/2021] [Indexed: 11/22/2022] Open
Abstract
Fragile X syndrome (FXS) is the most frequent form of inherited intellectual disability and the best-described monogenic cause of autism. CGG-repeat expansion in the FMR1 gene leads to FMR1 silencing, loss-of-expression of the Fragile X Mental Retardation Protein (FMRP), and is a common cause of FXS. Missense mutations in the FMR1 gene were also identified in FXS patients, including the recurrent FMRP-R138Q mutation. To investigate the mechanisms underlying FXS caused by this mutation, we generated a knock-in mouse model (Fmr1R138Q) expressing the FMRP-R138Q protein. We demonstrate that, in the hippocampus of the Fmr1R138Q mice, neurons show an increased spine density associated with synaptic ultrastructural defects and increased AMPA receptor-surface expression. Combining biochemical assays, high-resolution imaging, electrophysiological recordings, and behavioural testing, we also show that the R138Q mutation results in impaired hippocampal long-term potentiation and socio-cognitive deficits in mice. These findings reveal the functional impact of the FMRP-R138Q mutation in a mouse model of FXS.
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Affiliation(s)
- Marta Prieto
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France
| | | | | | | | | | - Marie Pronot
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France
| | | | | | - Norma Lattuada
- Università degli Studi di Milano, Dept. of Medical Biotechnology and Translational Medicine, Milan, Italy
| | | | | | - Magda Chafai
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France
| | | | | | - Frédéric Brau
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France
| | | | - Maura Francolini
- Università degli Studi di Milano, Dept. of Medical Biotechnology and Translational Medicine, Milan, Italy
| | - Barbara Bardoni
- Université Côte d'Azur, Inserm, CNRS, IPMC, Valbonne, France
| | - Yann Humeau
- University of Bordeaux, CNRS, IINS, Bordeaux, France
| | | | - Stéphane Martin
- Université Côte d'Azur, Inserm, CNRS, IPMC, Valbonne, France.
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32
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Berry-Kravis E, Filipink RA, Frye RE, Golla S, Morris SM, Andrews H, Choo TH, Kaufmann WE. Seizures in Fragile X Syndrome: Associations and Longitudinal Analysis of a Large Clinic-Based Cohort. Front Pediatr 2021; 9:736255. [PMID: 35036394 PMCID: PMC8756611 DOI: 10.3389/fped.2021.736255] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 10/07/2021] [Indexed: 11/15/2022] Open
Abstract
Fragile X syndrome (FXS), the most common inherited cause of intellectual disability, learning disability, and autism spectrum disorder, is associated with an increased prevalence of certain medical conditions including seizures. The goal of this study was to better understand seizures in individuals with FXS using the Fragile X Online Registry with Accessible Research Database, a multisite observational study initiated in 2012 involving FXS clinics in the Fragile X Clinic and Research Consortium. Seizure data were available for 1,607 participants, mostly male (77%) and white (74.5%). The overall prevalence of at least one seizure was 12%, with this rate being significantly higher in males than females (13.7 vs. 6.2%, p < 0.001). As compared to individuals with FXS without seizures, those with seizures were more likely to have autism spectrum disorder, current sleep apnea, later acquisition of expressive language, more severe intellectual disability, hyperactivity, irritability, and stereotyped movements. The mean age of seizure onset was 6.4 (SD 6.1) years of age with the great majority (>80%) having onset of seizures which was before 10. For those with epilepsy, about half (52%) had seizures for more than 3 years. This group was found to have greater cognitive and language impairment, but not behavioral disruptions, compared with those with seizures for <3 years. Antiepileptic drugs were more often used in males (60.6%) than females (34.8%), and females more often required more than one medication. The most commonly used anticonvulsants were oxcarbazepine, valproic acid, lamotrigine, and levetiracetam. The current study is the largest and first longitudinal study ever conducted to describe seizures in FXS. Overall, this study confirms previous reports of seizures in FXS and extends previous findings by further defining the cognitive and behavioral phenotype of those with epilepsy in FXS. Future studies should further investigate the natural history of seizures in FXS and the characteristics of seizures in FXS in adulthood.
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Affiliation(s)
- Elizabeth Berry-Kravis
- Department of Pediatrics, Rush University Medical Center, Chicago, IL, United States.,Department of Neurological Sciences, Rush University Medical Center, Chicago, IL, United States
| | - Robyn A Filipink
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Richard E Frye
- Barrow Neurological Institute at Phoenix Children's Hospital, Phoenix, AZ, United States.,Department of Child Health, University of Arizona College of Medicine-Phoenix, Phoenix, AZ, United States
| | - Sailaja Golla
- Division of Neurodevelopmental Medicine, Department of Neurology, Thompson Autism Center, Children's Hospital of California, University of Irvine, Orange, CA, United States
| | - Stephanie M Morris
- Division of Pediatric and Developmental Neurology, Department of Neurology, Washington University in St. Louis, St. Louis, MO, United States
| | - Howard Andrews
- Department of Biostatistics, Mailman School of Public Health, Columbia University Medical Center, New York, NY, United States
| | - Tse-Hwei Choo
- Department of Psychiatry, New York State Psychiatric Institute, Columbia University Medical Center, New York, NY, United States
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Zeidler S, Severijnen LA, de Boer H, van der Toorn EC, Ruivenkamp CAL, Bijlsma EK, Willemsen R. A missense variant in the nuclear export signal of the FMR1 gene causes intellectual disability. Gene 2020; 768:145298. [PMID: 33181255 DOI: 10.1016/j.gene.2020.145298] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 10/14/2020] [Accepted: 11/04/2020] [Indexed: 11/15/2022]
Abstract
Fragile X syndrome (FXS) is the most common monogenetic cause of intellectual disability and autism spectrum disorders. Mostly, FXS is caused by transcriptional silencing of the FMR1 gene due to a repeat expansion in the 5' UTR, and consequently lack of the protein product FMRP. However, in rare cases FXS is caused by other types of variants in the FMR1 gene. We describe a missense variant in the FMR1 gene, identified through whole-exome sequencing, in a boy with intellectual disability and behavioral problems. The variant is located in the FMRP's nuclear export signal (NES). We performed expression and localization studies of the variant in hair roots and HEK293 cells. Our results show normal expression but significant retention of the FMRP in the cells' nucleus. This finding suggests a possible FMRP reduction at its essential functional sites in the dendrites and the synaptic compartments and possible interference of other cellular processes in the nucleus. Together, this might lead to a FXS phenotype in the boy.
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Affiliation(s)
- Shimriet Zeidler
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands.
| | | | - Helen de Boer
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
| | | | - Claudia A L Ruivenkamp
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Emilia K Bijlsma
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands
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Sears JC, Broadie K. FMRP-PKA Activity Negative Feedback Regulates RNA Binding-Dependent Fibrillation in Brain Learning and Memory Circuitry. Cell Rep 2020; 33:108266. [PMID: 33053340 PMCID: PMC7590955 DOI: 10.1016/j.celrep.2020.108266] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 09/07/2020] [Accepted: 09/22/2020] [Indexed: 11/29/2022] Open
Abstract
Fragile X mental retardation protein (FMRP) promotes cyclic AMP (cAMP) signaling. Using an in vivo protein kinase A activity sensor (PKA-SPARK), we find that Drosophila FMRP (dFMRP) and human FMRP (hFMRP) enhance PKA activity in a central brain learning and memory center. Increasing neuronal PKA activity suppresses FMRP in Kenyon cells, demonstrating an FMRP-PKA negative feedback loop. A patient-derived R140Q FMRP point mutation mislocalizes PKA-SPARK activity, whereas deletion of the RNA-binding argi-nine-glycine-glycine (RGG) box (hFMRP-ΔRGG) produces fibrillar PKA-SPARK assemblies colocalizing with ribonucleoprotein (RNP) and aggregation (thioflavin T) markers, demonstrating fibrillar partitioning of cytosolic protein aggregates. hFMRP-ΔRGG reduces dFMRP levels, indicating RGG-independent regulation. Short-term hFMRP-ΔRGG induction produces activated PKA-SPARK puncta, whereas long induction drives fibrillar assembly. Elevated temperature disassociates hFMRP-ΔRGG aggregates and blocks activated PKA-SPARK localization. These results suggest that FMRP regulates compartmentalized signaling via complex assembly, directing PKA activity localization, with FMRP RGG box RNA binding restricting separation via low-complexity interactions. FMRP is required for brain cAMP induction and cAMP-dependent PKA activation, but the FMRP mechanism is uncharacterized. Sears and Broadie test FXS patient-derived and FMRP domain-deficient mutants to reveal conserved FMRP functions regulating PKA activation, subcellular localization, and reversible partitioning into elongated fibrillar assemblies in brain learning/ memory circuit neurons.
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Affiliation(s)
- James C Sears
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN 37235, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
| | - Kendal Broadie
- Vanderbilt Brain Institute, Vanderbilt University Medical Center, Nashville, TN 37235, USA; Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA; Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37235, USA; Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37235, USA.
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35
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Prieto M, Folci A, Martin S. Post-translational modifications of the Fragile X Mental Retardation Protein in neuronal function and dysfunction. Mol Psychiatry 2020; 25:1688-1703. [PMID: 31822816 DOI: 10.1038/s41380-019-0629-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/22/2019] [Accepted: 11/27/2019] [Indexed: 12/17/2022]
Abstract
The Fragile X Mental Retardation Protein (FMRP) is an RNA-binding protein essential to the regulation of local translation at synapses. In the mammalian brain, synapses are constantly formed and eliminated throughout development to achieve functional neuronal networks. At the molecular level, thousands of proteins cooperate to accomplish efficient neuronal communication. Therefore, synaptic protein levels and their functional interactions need to be tightly regulated. FMRP generally acts as a translational repressor of its mRNA targets. FMRP is the target of several post-translational modifications (PTMs) that dynamically regulate its function. Here we provide an overview of the PTMs controlling the FMRP function and discuss how their spatiotemporal interplay contributes to the physiological regulation of FMRP. Importantly, FMRP loss-of-function leads to Fragile X syndrome (FXS), a rare genetic developmental condition causing a range of neurological alterations including intellectual disability (ID), learning and memory impairments, autistic-like features and seizures. Here, we also explore the possibility that recently reported missense mutations in the FMR1 gene disrupt the PTM homoeostasis of FMRP, thus participating in the aetiology of FXS. This suggests that the pharmacological targeting of PTMs may be a promising strategy to develop innovative therapies for patients carrying such missense mutations.
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Affiliation(s)
- Marta Prieto
- Université Côte d'Azur, CNRS, IPMC, Valbonne, France
| | | | - Stéphane Martin
- Université Côte d'Azur, INSERM, CNRS, IPMC, Valbonne, France.
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36
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Bonnycastle K, Davenport EC, Cousin MA. Presynaptic dysfunction in neurodevelopmental disorders: Insights from the synaptic vesicle life cycle. J Neurochem 2020; 157:179-207. [PMID: 32378740 DOI: 10.1111/jnc.15035] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/14/2020] [Accepted: 04/22/2020] [Indexed: 12/11/2022]
Abstract
The activity-dependent fusion, retrieval and recycling of synaptic vesicles is essential for the maintenance of neurotransmission. Until relatively recently it was believed that most mutations in genes that were essential for this process would be incompatible with life, because of this fundamental role. However, an ever-expanding number of mutations in this very cohort of genes are being identified in individuals with neurodevelopmental disorders, including autism, intellectual disability and epilepsy. This article will summarize the current state of knowledge linking mutations in presynaptic genes to neurodevelopmental disorders by sequentially covering the various stages of the synaptic vesicle life cycle. It will also discuss how perturbations of specific stages within this recycling process could translate into human disease. Finally, it will also provide perspectives on the potential for future therapy that are targeted to presynaptic function.
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Affiliation(s)
- Katherine Bonnycastle
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Elizabeth C Davenport
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Michael A Cousin
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK.,Muir Maxwell Epilepsy Centre, University of Edinburgh, Edinburgh, UK.,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
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37
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Golden CEM, Breen MS, Koro L, Sonar S, Niblo K, Browne A, Burlant N, Di Marino D, De Rubeis S, Baxter MG, Buxbaum JD, Harony-Nicolas H. Deletion of the KH1 Domain of Fmr1 Leads to Transcriptional Alterations and Attentional Deficits in Rats. Cereb Cortex 2020; 29:2228-2244. [PMID: 30877790 PMCID: PMC6458915 DOI: 10.1093/cercor/bhz029] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 12/11/2018] [Accepted: 02/06/2019] [Indexed: 12/27/2022] Open
Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene. It is a leading monogenic cause of autism spectrum disorder and inherited intellectual disability and is often comorbid with attention deficits. Most FXS cases are due to an expansion of CGG repeats leading to suppressed expression of fragile X mental retardation protein (FMRP), an RNA-binding protein involved in mRNA metabolism. We found that the previously published Fmr1 knockout rat model of FXS expresses an Fmr1 transcript with an in-frame deletion of exon 8, which encodes for the K-homology (KH) RNA-binding domain, KH1. Notably, 3 pathogenic missense mutations associated with FXS lie in the KH domains. We observed that the deletion of exon 8 in rats leads to attention deficits and to alterations in transcriptional profiles within the medial prefrontal cortex (mPFC), which map to 2 weighted gene coexpression network modules. These modules are conserved in human frontal cortex and enriched for known FMRP targets. Hub genes in these modules represent potential therapeutic targets for FXS. Taken together, these findings indicate that attentional testing might be a reliable cross-species tool for investigating FXS and identify dysregulated conserved gene networks in a relevant brain region.
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Affiliation(s)
- Carla E M Golden
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Michael S Breen
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Lacin Koro
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sankalp Sonar
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Kristi Niblo
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Andrew Browne
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Natalie Burlant
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Daniele Di Marino
- Faculty of Biomedical Sciences, Institute of Computational Science, Center for Computational Medicine in Cardiology, Università della Svizzera Italiana (USI), Lugano, Switzerland.,Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy
| | - Silvia De Rubeis
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Mark G Baxter
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Joseph D Buxbaum
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hala Harony-Nicolas
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Seaver Autism Center for Research and Treatment, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Mindich Child Health and Development Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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Loss of the KH1 domain of FMR1 in humans due to a synonymous variant causes global developmental retardation. Gene 2020; 753:144793. [PMID: 32446918 DOI: 10.1016/j.gene.2020.144793] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/30/2020] [Accepted: 05/18/2020] [Indexed: 11/20/2022]
Abstract
BACKGROUND Fragile X syndrome (FXS) is a monogenic disorder and a common cause of intellectual disability (ID). Up to now, very few pathological variants other than the typical CGG-repeat expansion have been reported in the FMR1 gene. METHODS A panel of 56 intellectual disability (ID) genes including the FMR1 gene was sequenced in a cohort of 300 patients with unexplained ID. To determine the effect of a new FMR1 variant, total RNA from peripheral blood cells was reverse transcribed, amplified by polymerase chain reaction and sequenced. RESULTS We report a novel G to A point variant (c.801G > A) located at the last nucleotide of exon 8 in the FMR1 gene in one patient with ID. Direct sequencing of the RT-PCR products revealed that the transcript from the allele with G to A variant skips exon 8 entirely, resulting in a joining of exons 7 and 9. Skipping of exon 8 may result in an abnormal FMR1 protein (FMRP), which removes the highly conserved region that encoding the KH1 domain of FMRP. CONCLUSIONS This report describes for the first time that a synonymous variant in the FMR1 gene is associated with an error in mRNA processing, leading preferentially to the production of an aberrant transcript without exon 8. This splice variant was associated with an unspecific clinical presentation, suggesting the need for more detailed investigation of silent variants in ID patients with a large spectrum of phenotypes.
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McCullagh EA, Rotschafer SE, Auerbach BD, Klug A, Kaczmarek LK, Cramer KS, Kulesza RJ, Razak KA, Lovelace JW, Lu Y, Koch U, Wang Y. Mechanisms underlying auditory processing deficits in Fragile X syndrome. FASEB J 2020; 34:3501-3518. [PMID: 32039504 DOI: 10.1096/fj.201902435r] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 12/31/2019] [Accepted: 01/18/2020] [Indexed: 01/14/2023]
Abstract
Autism spectrum disorders (ASD) are strongly associated with auditory hypersensitivity or hyperacusis (difficulty tolerating sounds). Fragile X syndrome (FXS), the most common monogenetic cause of ASD, has emerged as a powerful gateway for exploring underlying mechanisms of hyperacusis and auditory dysfunction in ASD. This review discusses examples of disruption of the auditory pathways in FXS at molecular, synaptic, and circuit levels in animal models as well as in FXS individuals. These examples highlight the involvement of multiple mechanisms, from aberrant synaptic development and ion channel deregulation of auditory brainstem circuits, to impaired neuronal plasticity and network hyperexcitability in the auditory cortex. Though a relatively new area of research, recent discoveries have increased interest in auditory dysfunction and mechanisms underlying hyperacusis in this disorder. This rapidly growing body of data has yielded novel research directions addressing critical questions regarding the timing and possible outcomes of human therapies for auditory dysfunction in ASD.
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Affiliation(s)
- Elizabeth A McCullagh
- Department of Physiology and Biophysics, University of Colorado Anschutz, Aurora, CO, USA.,Department of Integrative Biology, Oklahoma State University, Stillwater, OK, USA
| | - Sarah E Rotschafer
- Department of Neurobiology and Behavior, University of California, Irvine, CA, USA.,Department of Biomedical Sciences, Mercer University School of Medicine, Savannah, GA, USA
| | - Benjamin D Auerbach
- Center for Hearing and Deafness, Department of Communicative Disorders & Sciences, SUNY at Buffalo, Buffalo, NY, USA
| | - Achim Klug
- Department of Physiology and Biophysics, University of Colorado Anschutz, Aurora, CO, USA
| | - Leonard K Kaczmarek
- Departments of Pharmacology and Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Karina S Cramer
- Department of Neurobiology and Behavior, University of California, Irvine, CA, USA
| | - Randy J Kulesza
- Department of Anatomy, Lake Erie College of Osteopathic Medicine, Erie, PA, USA
| | - Khaleel A Razak
- Department of Psychology, University of California, Riverside, CA, USA
| | | | - Yong Lu
- Department of Anatomy and Neurobiology, College of Medicine, Northeast Ohio Medical University, Rootstown, OH, USA
| | - Ursula Koch
- Institute of Biology, Neurophysiology, Freie Universität Berlin, Berlin, Germany
| | - Yuan Wang
- Department of Biomedical Sciences, Program in Neuroscience, Florida State University, Tallahassee, FL, USA
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40
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The loss of β adrenergic receptor mediated release potentiation in a mouse model of fragile X syndrome. Neurobiol Dis 2019; 130:104482. [DOI: 10.1016/j.nbd.2019.104482] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/17/2019] [Accepted: 05/22/2019] [Indexed: 11/23/2022] Open
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41
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Disruption of GpI mGluR-Dependent Cav2.3 Translation in a Mouse Model of Fragile X Syndrome. J Neurosci 2019; 39:7453-7464. [PMID: 31350260 DOI: 10.1523/jneurosci.1443-17.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 06/13/2019] [Accepted: 06/19/2019] [Indexed: 11/21/2022] Open
Abstract
Fragile X syndrome (FXS) is an inherited intellectual impairment that results from the loss of fragile X mental retardation protein (FMRP), an mRNA binding protein that regulates mRNA translation at synapses. The absence of FMRP leads to neuronal and circuit-level hyperexcitability that is thought to arise from the aberrant expression and activity of voltage-gated ion channels, although the identification and characterization of these ion channels have been limited. Here, we show that FMRP binds the mRNA of the R-type voltage-gated calcium channel Cav2.3 in mouse brain synaptoneurosomes and represses Cav2.3 translation under basal conditions. Consequently, in hippocampal neurons from male and female FMRP KO mice, we find enhanced Cav2.3 protein expression by western blotting and abnormally large R currents in whole-cell voltage-clamp recordings. In agreement with previous studies showing that FMRP couples Group I metabotropic glutamate receptor (GpI mGluR) signaling to protein translation, we find that GpI mGluR stimulation results in increased Cav2.3 translation and R current in hippocampal neurons which is disrupted in FMRP KO mice. Thus, FMRP serves as a key translational regulator of Cav2.3 expression under basal conditions and in response to GpI mGluR stimulation. Loss of regulated Cav2.3 expression could underlie the neuronal hyperactivity and aberrant calcium spiking in FMRP KO mice and contribute to FXS, potentially serving as a novel target for future therapeutic strategies.SIGNIFICANCE STATEMENT Patients with fragile X syndrome (FXS) exhibit signs of neuronal and circuit hyperexcitability, including anxiety and hyperactive behavior, attention deficit disorder, and seizures. FXS is caused by the loss of fragile X mental retardation protein (FMRP), an mRNA binding protein, and the neuronal hyperexcitability observed in the absence of FMRP likely results from its ability to regulate the expression and activity of voltage-gated ion channels. Here we find that FMRP serves as a key translational regulator of the voltage-gated calcium channel Cav2.3 under basal conditions and following activity. Cav2.3 impacts cellular excitability and calcium signaling, and the alterations in channel translation and expression observed in the absence of FMRP could contribute to the neuronal hyperactivity that underlies FXS.
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Abstract
Fragile X syndrome (FXS) is a neurodevelopmental disorder that causes intellectual disability. It is a leading known genetic cause of autism. In addition to cognitive, social, and communication deficits, humans with FXS demonstrate abnormal sensory processing including sensory hypersensitivity. Sensory hypersensitivity commonly manifests as auditory, tactile, or visual defensiveness or avoidance. Clinical, behavioral, and electrophysiological studies consistently show auditory hypersensitivity, impaired habituation to repeated sounds, and reduced auditory attention in humans with FXS. Children with FXS also exhibit significant visuospatial impairments. Studies in infants and toddlers with FXS have documented impairments in processing texture-defined motion stimuli, temporal flicker, perceiving ordinal numerical sequence, and the ability to maintain the identity of dynamic object information during occlusion. Consistent with the observations in humans with FXS, fragile X mental retardation 1 ( Fmr1) gene knockout (KO) rodent models of FXS also show seizures, abnormal visual-evoked responses, auditory hypersensitivity, and abnormal processing at multiple levels of the auditory system, including altered acoustic startle responses. Among other sensory symptoms, individuals with FXS exhibit tactile defensiveness. Fmr1 KO mice also show impaired encoding of tactile stimulation frequency and larger size of receptive fields in the somatosensory cortex. Since sensory deficits are relatively more tractable from circuit mechanisms and developmental perspectives than more complex social behaviors, the focus of this review is on clinical, functional, and structural studies that outline the auditory, visual, and somatosensory processing deficits in FXS. The similarities in sensory phenotypes between humans with FXS and animal models suggest a likely conservation of basic sensory processing circuits across species and may provide a translational platform to not just develop biomarkers but also to understand underlying mechanisms. We argue that preclinical studies in animal models of FXS can facilitate the ongoing search for new therapeutic approaches in FXS by understanding mechanisms of basic sensory processing circuits and behaviors that are conserved across species.
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Affiliation(s)
- Maham Rais
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA
| | - Devin K Binder
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA
| | - Khaleel A Razak
- 2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA.,4 Psychology Department, University of California Riverside, CA, USA
| | - Iryna M Ethell
- 1 Division of Biomedical Sciences, University of California Riverside School of Medicine, CA, USA.,2 Biomedical Sciences Graduate Program, University of California Riverside, CA, USA.,3 Neuroscience Graduate Program, University of California Riverside, CA, USA
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43
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Bodaleo F, Tapia-Monsalves C, Cea-Del Rio C, Gonzalez-Billault C, Nunez-Parra A. Structural and Functional Abnormalities in the Olfactory System of Fragile X Syndrome Models. Front Mol Neurosci 2019; 12:135. [PMID: 31191246 PMCID: PMC6548058 DOI: 10.3389/fnmol.2019.00135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 05/09/2019] [Indexed: 12/18/2022] Open
Abstract
Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability. It is produced by mutation of the Fmr1 gene that encodes for the Fragile Mental Retardation Protein (FMRP), an important RNA-binding protein that regulates the expression of multiple proteins located in neuronal synapses. Individuals with FXS exhibit abnormal sensory information processing frequently leading to hypersensitivity across sensory modalities and consequently a wide array of behavioral symptoms. Insects and mammals engage primarily their sense of smell to create proper representations of the external world and guide adequate decision-making processes. This feature in combination with the exquisitely organized neuronal circuits found throughout the olfactory system (OS) and the wide expression of FMRP in brain regions that process olfactory information makes it an ideal model to study sensory alterations in FXS models. In the last decade several groups have taken advantage of these features and have used the OS of fruit fly and rodents to understand neuronal alteration giving rise to sensory perception issues. In this review article, we will discuss molecular, morphological and physiological aspects of the olfactory information processing in FXS models. We will highlight the decreased inhibitory/excitatory synaptic balance and the diminished synaptic plasticity found in this system resulting in behavioral alteration of individuals in the presence of odorant stimuli.
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Affiliation(s)
- Felipe Bodaleo
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Science, Universidad de Chile, Santiago, Chile.,Geroscience Center for Brain Health and Metabolism (GERO), Santiago, Chile
| | | | - Christian Cea-Del Rio
- Laboratory of Neurophysiopathology, Centro de Investigacion Biomedica y Aplicada (CIBAP), School of Medicine, Universidad de Santiago de Chile, Santiago, Chile
| | - Christian Gonzalez-Billault
- Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Science, Universidad de Chile, Santiago, Chile.,Geroscience Center for Brain Health and Metabolism (GERO), Santiago, Chile.,The Buck Institute for Research on Aging, Novato, CA, United States
| | - Alexia Nunez-Parra
- Department of Biology, Faculty of Science, Universidad de Chile, Santiago, Chile.,Cell Physiology Center, Universidad de Chile, Santiago, Chile
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Kinase pathway inhibition restores PSD95 induction in neurons lacking fragile X mental retardation protein. Proc Natl Acad Sci U S A 2019; 116:12007-12012. [PMID: 31118285 DOI: 10.1073/pnas.1812056116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Fragile X syndrome (FXS) is the leading monogenic cause of autism and intellectual disability. FXS is caused by loss of expression of fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates translation of numerous mRNA targets, some of which are present at synapses. While protein synthesis deficits have long been postulated as an etiology of FXS, how FMRP loss affects distributions of newly synthesized proteins is unknown. Here we investigated the role of FMRP in regulating expression of new copies of the synaptic protein PSD95 in an in vitro model of synaptic plasticity. We find that local BDNF application promotes persistent accumulation of new PSD95 at stimulated synapses and dendrites of cultured neurons, and that this accumulation is absent in FMRP-deficient mouse neurons. New PSD95 accumulation at sites of BDNF stimulation does not require known mechanisms regulating FMRP-mRNA interactions but instead requires the PI3K-mTORC1-S6K1 pathway. Surprisingly, in FMRP-deficient neurons, BDNF induction of new PSD95 accumulation can be restored by mTORC1-S6K1 blockade, suggesting that constitutively high mTORC1-S6K1 activity occludes PSD95 regulation by BDNF and that alternative pathways exist to mediate induction when mTORC1-S6K1 is inhibited. This study provides direct evidence for deficits in local protein synthesis and accumulation of newly synthesized protein in response to local stimulation in FXS, and supports mTORC1-S6K1 pathway inhibition as a potential therapeutic approach for FXS.
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Modulators of Kv3 Potassium Channels Rescue the Auditory Function of Fragile X Mice. J Neurosci 2019; 39:4797-4813. [PMID: 30936239 DOI: 10.1523/jneurosci.0839-18.2019] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 03/15/2019] [Accepted: 03/26/2019] [Indexed: 11/21/2022] Open
Abstract
Fragile X syndrome (FXS) is characterized by hypersensitivity to sensory stimuli, including environmental sounds. We compared the auditory brainstem response (ABR) recorded in vivo in mice lacking the gene (Fmr1 -/y ) for fragile X mental retardation protein (FMRP) with that in wild-type animals. We found that ABR wave I, which represents input from the auditory nerve, is reduced in Fmr1 -/y animals, but only at high sound levels. In contrast, wave IV, which represents the activity of auditory brainstem nuclei is enhanced at all sound levels, suggesting that loss of FMRP alters the central processing of auditory signals. Current-clamp recordings of neurons in the medial nucleus of the trapezoid body in the auditory brainstem revealed that, in contrast to neurons from wild-type animals, sustained depolarization triggers repetitive firing rather than a single action potential. In voltage-clamp recordings, K+ currents that activate at positive potentials ("high-threshold" K+ currents), which are required for high-frequency firing and are carried primarily by Kv3.1 channels, are elevated in Fmr1 -/y mice, while K+ currents that activate near the resting potential and inhibit repetitive firing are reduced. We therefore tested the effects of AUT2 [((4-({5-[(4R)-4-ethyl-2,5-dioxo-1-imidazolidinyl]-2-pyridinyl}oxy)-2-(1-methylethyl) benzonitrile], a compound that modulates Kv3.1 channels. AUT2 reduced the high-threshold K+ current and increased the low-threshold K+ currents in neurons from Fmr1 -/y animals by shifting the activation of the high-threshold current to more negative potentials. This reduced the firing rate and, in vivo, restored wave IV of the ABR. Our results from animals of both sexes suggest that the modulation of the Kv3.1 channel may have potential for the treatment of sensory hypersensitivity in patients with FXS.SIGNIFICANCE STATEMENT mRNA encoding the Kv3.1 potassium channel was one of the first described targets of the fragile X mental retardation protein (FMRP). Fragile X syndrome is caused by loss of FMRP and, in humans and mice, causes hypersensitivity to auditory stimuli. We found that components of the auditory brain response (ABR) corresponding to auditory brainstem activity are enhanced in mice lacking FMRP. This is accompanied by hyperexcitability and altered potassium currents in auditory brainstem neurons. Treatment with a drug that alters the voltage dependence of Kv3.1 channels normalizes the imbalance of potassium currents, as well as ABR responses in vivo, suggesting that such compounds may be effective in treating some symptoms of fragile X syndrome.
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A Species-Correlated Transitional Residue D132 on Human FMRP Plays a Role in Nuclear Localization via an RNA-Dependent Interaction With PABP1. Neuroscience 2019; 404:282-296. [DOI: 10.1016/j.neuroscience.2019.01.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 12/16/2018] [Accepted: 01/17/2019] [Indexed: 11/22/2022]
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47
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FERREIRA JORGEF, BATISTA JACQUELINES, FANTIN CLEITON. Screening for FMR1 expanded alleles in patients with Autism Spectrum Disorders in Manaus, Northern Brazil. AN ACAD BRAS CIENC 2019; 91:e20180882. [DOI: 10.1590/0001-3765201920180882] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 10/04/2018] [Indexed: 11/22/2022] Open
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Wang C, Ge L, Wu J, Wang X, Yuan L. MiR-219 represses expression of dFMR1 in Drosophila melanogaster. Life Sci 2018; 218:31-37. [PMID: 30528775 DOI: 10.1016/j.lfs.2018.12.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 11/27/2018] [Accepted: 12/05/2018] [Indexed: 11/19/2022]
Abstract
AIMS Fragile X mental retardation protein (FMRP) plays a vital role in mRNA trafficking and translation inhibition to regulate the synthesis of local proteins in neuronal axons and dendritic terminals. However, there are no reports on microRNA (miRNA)-mediated regulation of FMRP levels in Drosophila. Here, we aimed to identify miRNAs regulating FMRP levels in Drosophila. MAIN METHODS Using online software, we predicted and selected 11 miRNAs potentially acting on the Drosophila fragile X mental retardation 1 (dFMR1) transcript. These candidates were screened for modulation of dFMR1 transcript levels at the cellular level using a dual luciferase reporter system. In addition, we constructed a transgenic Drosophila model overexpressing miR-219 in the nervous system and quantified dFMRP by western blotting. The neuromuscular junction phenotype in the model was studied by immunofluorescence staining. KEY FINDINGS Among the 11 miRNAs screened, miR-219 and miR-960 reduced luciferase gene activity by binding to the 3'-UTR of the dFMR1 transcript. Mutation of the miR-219 or miR-960 binding sites on the transcript resulted in complete or partial elimination of the miRNA-induced repression. Western blots revealed that dFMRP expression was decreased in the miR-219 overexpression model (Elav>miR-219). Drosophila larvae overexpressing miR-219 showed morphological abnormalities at the neuromuscular junction (increased synaptic boutons and synaptic branches). This finding is consistent with some phenotypes observed in dfmr1 mutants. SIGNIFICANCE Our results suggest that miR-219 regulates dFMR1 expression in Drosophila and is involved in fragile X syndrome pathogenesis. Collectively, these findings expand the current understanding of miRNA-mediated regulation of target molecule-related functions.
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Affiliation(s)
- Chao Wang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China; State Key Laboratory for Pharmaceutical Biotechnology, Nanjing University, Nanjing 210023, China
| | - Liang Ge
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Jianban Wu
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Xuan Wang
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Liudi Yuan
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Institute of Life Sciences, Southeast University, Nanjing 210096, China; School of Medicine, Southeast University, Nanjing 210009, China.
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Voltage-Independent SK-Channel Dysfunction Causes Neuronal Hyperexcitability in the Hippocampus of Fmr1 Knock-Out Mice. J Neurosci 2018; 39:28-43. [PMID: 30389838 DOI: 10.1523/jneurosci.1593-18.2018] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 10/08/2018] [Accepted: 10/25/2018] [Indexed: 12/11/2022] Open
Abstract
Neuronal hyperexcitability is one of the major characteristics of fragile X syndrome (FXS), yet the molecular mechanisms of this critical dysfunction remain poorly understood. Here we report a major role of voltage-independent potassium (K+)-channel dysfunction in hyperexcitability of CA3 pyramidal neurons in Fmr1 knock-out (KO) mice. We observed a reduction of voltage-independent small conductance calcium (Ca2+)-activated K+ (SK) currents in both male and female mice, leading to decreased action potential (AP) threshold and reduced medium afterhyperpolarization. These SK-channel-dependent deficits led to markedly increased AP firing and abnormal input-output signal transmission of CA3 pyramidal neurons. The SK-current defect was mediated, at least in part, by loss of FMRP interaction with the SK channels (specifically the SK2 isoform), without changes in channel expression. Intracellular application of selective SK-channel openers or a genetic reintroduction of an N-terminal FMRP fragment lacking the ability to associate with polyribosomes normalized all observed excitability defects in CA3 pyramidal neurons of Fmr1 KO mice. These results suggest that dysfunction of voltage-independent SK channels is the primary cause of CA3 neuronal hyperexcitability in Fmr1 KO mice and support the critical translation-independent role for the fragile X mental retardation protein as a regulator of neural excitability. Our findings may thus provide a new avenue to ameliorate hippocampal excitability defects in FXS.SIGNIFICANCE STATEMENT Despite two decades of research, no effective treatment is currently available for fragile X syndrome (FXS). Neuronal hyperexcitability is widely considered one of the hallmarks of FXS. Excitability research in the FXS field has thus far focused primarily on voltage-gated ion channels, while contributions from voltage-independent channels have been largely overlooked. Here we report that voltage-independent small conductance calcium-activated potassium (SK)-channel dysfunction causes hippocampal neuron hyperexcitability in the FXS mouse model. Our results support the idea that translation-independent function of fragile X mental retardation protein has a major role in regulating ion-channel activity, specifically the SK channels, in hyperexcitability defects in FXS. Our findings may thus open a new direction to ameliorate hippocampal excitability defects in FXS.
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50
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Li Y, Shen M, Stockton ME, Zhao X. Hippocampal deficits in neurodevelopmental disorders. Neurobiol Learn Mem 2018; 165:106945. [PMID: 30321651 DOI: 10.1016/j.nlm.2018.10.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 10/08/2018] [Accepted: 10/11/2018] [Indexed: 12/17/2022]
Abstract
Neurodevelopmental disorders result from impaired development or maturation of the central nervous system. Both genetic and environmental factors can contribute to the pathogenesis of these disorders; however, the exact causes are frequently complex and unclear. Individuals with neurodevelopmental disorders may have deficits with diverse manifestations, including challenges with sensory function, motor function, learning, memory, executive function, emotion, anxiety, and social ability. Although these functions are mediated by multiple brain regions, many of them are dependent on the hippocampus. Extensive research supports important roles of the mammalian hippocampus in learning and cognition. In addition, with its high levels of activity-dependent synaptic plasticity and lifelong neurogenesis, the hippocampus is sensitive to experience and exposure and susceptible to disease and injury. In this review, we first summarize hippocampal deficits seen in several human neurodevelopmental disorders, and then discuss hippocampal impairment including hippocampus-dependent behavioral deficits found in animal models of these neurodevelopmental disorders.
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Affiliation(s)
- Yue Li
- Institute of Traditional Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China; Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Minjie Shen
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Michael E Stockton
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA
| | - Xinyu Zhao
- Waisman Center, University of Wisconsin-Madison, Madison, WI 53705, USA; Department of Neuroscience, University of Wisconsin-Madison, Madison, WI 53705, USA.
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