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Jones AG, Aquilino M, Tinker RJ, Duncan L, Jenkins Z, Carvill GL, DeWard SJ, Grange DK, Hajianpour MJ, Halliday BJ, Holder-Espinasse M, Horvath J, Maitz S, Nigro V, Morleo M, Paul V, Spencer C, Esterhuizen AI, Polster T, Spano A, Gómez-Lozano I, Kumar A, Poke G, Phillips JA, Underhill HR, Gimenez G, Namba T, Robertson SP. Clustered de novo start-loss variants in GLUL result in a developmental and epileptic encephalopathy via stabilization of glutamine synthetase. Am J Hum Genet 2024; 111:729-741. [PMID: 38579670 PMCID: PMC11023914 DOI: 10.1016/j.ajhg.2024.03.005] [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: 12/19/2023] [Revised: 03/05/2024] [Accepted: 03/06/2024] [Indexed: 04/07/2024] Open
Abstract
Glutamine synthetase (GS), encoded by GLUL, catalyzes the conversion of glutamate to glutamine. GS is pivotal for the generation of the neurotransmitters glutamate and gamma-aminobutyric acid and is the primary mechanism of ammonia detoxification in the brain. GS levels are regulated post-translationally by an N-terminal degron that enables the ubiquitin-mediated degradation of GS in a glutamine-induced manner. GS deficiency in humans is known to lead to neurological defects and death in infancy, yet how dysregulation of the degron-mediated control of GS levels might affect neurodevelopment is unknown. We ascertained nine individuals with severe developmental delay, seizures, and white matter abnormalities but normal plasma and cerebrospinal fluid biochemistry with de novo variants in GLUL. Seven out of nine were start-loss variants and two out of nine disrupted 5' UTR splicing resulting in splice exclusion of the initiation codon. Using transfection-based expression systems and mass spectrometry, these variants were shown to lead to translation initiation of GS from methionine 18, downstream of the N-terminal degron motif, resulting in a protein that is stable and enzymatically competent but insensitive to negative feedback by glutamine. Analysis of human single-cell transcriptomes demonstrated that GLUL is widely expressed in neuro- and glial-progenitor cells and mature astrocytes but not in post-mitotic neurons. One individual with a start-loss GLUL variant demonstrated periventricular nodular heterotopia, a neuronal migration disorder, yet overexpression of stabilized GS in mice using in utero electroporation demonstrated no migratory deficits. These findings underline the importance of tight regulation of glutamine metabolism during neurodevelopment in humans.
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Affiliation(s)
- Amy G Jones
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Matilde Aquilino
- Neuroscience Center, HiLIFE - Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Rory J Tinker
- Vanderbilt University Medical Center, Nashville, TN, USA
| | - Laura Duncan
- Center for Individualized Medicine, Mayo Clinic, Jacksonville, FL, USA
| | - Zandra Jenkins
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Gemma L Carvill
- Department of Neurology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | | | | | | | - Benjamin J Halliday
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | | | | | - Silvia Maitz
- Medical Genetics Service, Oncology Department of Southern Switzerland, Ente Ospedaliero Cantonale, Lugano, Switzerland
| | - Vincenzo Nigro
- Department of Precision Medicine, University of Campania "Luigi Vanvitelli," Naples, Italy
| | - Manuela Morleo
- Department of Precision Medicine, University of Campania "Luigi Vanvitelli," Naples, Italy
| | | | - Careni Spencer
- Division of Human Genetics, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; Department of Medicine, Division of Human Genetics, Groote Schuur Hospital, Cape Town, South Africa
| | - Alina I Esterhuizen
- Division of Human Genetics, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa; Neuroscience Institute, University of Cape Town, Cape Town, South Africa; National Health Laboratory Service, Groote Schuur Hospital, Cape Town, South Africa
| | - Tilman Polster
- Department of Epileptology (Krankenhaus Mara, Bethel Epilepsy Center) Medical School OWL, Bielefeld University, Bielefeld, Germany
| | - Alice Spano
- Maggiore Della Carità Hospital, Novara, Italy
| | - Inés Gómez-Lozano
- Neuroscience Center, HiLIFE - Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Abhishek Kumar
- Centre for Protein Research, University of Otago, Dunedin, New Zealand
| | - Gemma Poke
- Genetics Health Service New Zealand, Wellington Hospital, Wellington, New Zealand
| | | | | | - Gregory Gimenez
- Department of Pathology, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
| | - Takashi Namba
- Neuroscience Center, HiLIFE - Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland
| | - Stephen P Robertson
- Department of Women's and Children's Health, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand.
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Eidhof I, Krebbers A, van de Warrenburg B, Schenck A. Ataxia-associated DNA repair genes protect the Drosophila mushroom body and locomotor function against glutamate signaling-associated damage. Front Neural Circuits 2023; 17:1148947. [PMID: 37476399 PMCID: PMC10354283 DOI: 10.3389/fncir.2023.1148947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 06/20/2023] [Indexed: 07/22/2023] Open
Abstract
The precise control of motor movements is of fundamental importance to all behaviors in the animal kingdom. Efficient motor behavior depends on dedicated neuronal circuits - such as those in the cerebellum - that are controlled by extensive genetic programs. Autosomal recessive cerebellar ataxias (ARCAs) provide a valuable entry point into how interactions between genetic programs maintain cerebellar motor circuits. We previously identified a striking enrichment of DNA repair genes in ARCAs. How dysfunction of ARCA-associated DNA repair genes leads to preferential cerebellar dysfunction and impaired motor function is however unknown. The expression of ARCA DNA repair genes is not specific to the cerebellum. Only a limited number of animal models for DNA repair ARCAs exist, and, even for these, the interconnection between DNA repair defects, cerebellar circuit dysfunction, and motor behavior is barely established. We used Drosophila melanogaster to characterize the function of ARCA-associated DNA repair genes in the mushroom body (MB), a structure in the Drosophila central brain that shares structural features with the cerebellum. Here, we demonstrate that the MB is required for efficient startle-induced and spontaneous motor behaviors. Inhibition of synaptic transmission and loss-of-function of ARCA-associated DNA repair genes in the MB affected motor behavior in several assays. These motor deficits correlated with increased levels of MB DNA damage, MB Kenyon cell apoptosis and/or alterations in MB morphology. We further show that expression of genes involved in glutamate signaling pathways are highly, specifically, and persistently elevated in the postnatal human cerebellum. Manipulation of glutamate signaling in the MB induced motor defects, Kenyon cell DNA damage and apoptosis. Importantly, pharmacological reduction of glutamate signaling in the ARCA DNA repair models rescued the identified motor deficits, suggesting a role for aberrant glutamate signaling in ARCA-DNA repair disorders. In conclusion, our data highlight the importance of ARCA-associated DNA repair genes and glutamate signaling pathways to the cerebellum, the Drosophila MB and motor behavior. We propose that glutamate signaling may confer preferential cerebellar vulnerability in ARCA-associated DNA repair disorders. Targeting glutamate signaling could provide an exciting therapeutic entry point in this large group of so far untreatable disorders.
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Affiliation(s)
- Ilse Eidhof
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands
| | - Alina Krebbers
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands
| | - Bart van de Warrenburg
- Department of Neurology, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands
| | - Annette Schenck
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, Netherlands
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Urinary mRNA Expression of Glomerular Podocyte Markers in Glomerular Disease and Renal Transplant. Diagnostics (Basel) 2021; 11:diagnostics11081499. [PMID: 34441433 PMCID: PMC8392587 DOI: 10.3390/diagnostics11081499] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/10/2021] [Accepted: 08/11/2021] [Indexed: 11/20/2022] Open
Abstract
The research of novel markers in urinary samples, for the description of renal damage, is of high interest, and several works demonstrated the value of urinary mRNA quantification for the search of events related to renal disease or affecting the outcome of transplant kidneys. In the present pilot study, a comparison of the urine mRNA expression of specific podocyte markers among patients who had undergone clinical indication to renal transplanted (RTx, n = 20) and native (N, n = 18) renal biopsy was performed. The aim of this work was to identify genes involved in podocytes signaling and cytoskeletal regulation (NPHS1, NPHS2, SYNPO, WT1, TRPC6, GRM1, and NEUROD) in respect to glomerular pathology. We considered some genes relevant for podocytes signaling and for the function of the glomerular filter applying an alternative normalization approach. Our results demonstrate the WT1 urinary mRNA increases in both groups and it is helpful for podocyte normalization. Furthermore, an increase in the expression of TRPC6 after all kinds of normalizations was observed. According to our data, WT1 normalization might be considered an alternative approach to correct the expression of urinary mRNA. In addition, our study underlines the importance of slit diaphragm proteins involved in calcium disequilibrium, such as TRPC6.
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Huang M, Verbeek DS. Why do so many genetic insults lead to Purkinje Cell degeneration and spinocerebellar ataxia? Neurosci Lett 2018; 688:49-57. [PMID: 29421540 DOI: 10.1016/j.neulet.2018.02.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/02/2018] [Indexed: 12/29/2022]
Abstract
The genetically heterozygous spinocerebellar ataxias are all characterized by cerebellar atrophy and pervasive Purkinje Cell degeneration. Up to date, more than 35 functionally diverse spinocerebellar ataxia genes have been identified. The main question that remains yet unsolved is why do some many genetic insults lead to Purkinje Cell degeneration and spinocerebellar ataxia? To address this question it is important to identify intrinsic pathways important for Purkinje Cell function and survival. In this review, we discuss the current consensus on shared mechanisms underlying the pervasive Purkinje Cell loss in spinocerebellar ataxia. Additionally, using recently published cell type specific expression data, we identified several Purkinje Cell-specific genes and discuss how the corresponding pathways might underlie the vulnerability of Purkinje Cells in response to the diverse genetic insults causing spinocerebellar ataxia.
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Affiliation(s)
- Miaozhen Huang
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands
| | - Dineke S Verbeek
- University of Groningen, University Medical Center Groningen, Department of Genetics, Groningen, The Netherlands.
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