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Dainelli A, Iacomino M, Rossato S, Bugin S, Traverso M, Severino M, Gustincich S, Capra V, Di Duca M, Zara F, Scala M, Striano P. Refining the electroclinical spectrum of NPRL3-related epilepsy: A novel multiplex family and literature review. Epilepsia Open 2023; 8:1314-1330. [PMID: 37491868 PMCID: PMC10690669 DOI: 10.1002/epi4.12798] [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: 02/20/2023] [Accepted: 07/17/2023] [Indexed: 07/27/2023] Open
Abstract
OBJECTIVE NPRL3-related epilepsy (NRE) is an emerging condition set within the wide GATOR-1 spectrum with a particularly heterogeneous and elusive phenotypic expression. Here, we delineated the genotype-phenotype spectrum of NRE, reporting an illustrative familial case and reviewing pertinent literature. METHODS Through exome sequencing (ES), we investigated a 12-year-old girl with recurrent focal motor seizures during sleep, suggestive of sleep-related hypermotor epilepsy (SHE), and a family history of epilepsy in siblings. Variant segregation analysis was performed by Sanger sequencing. All previously published NRE patients were thoroughly reviewed and their electroclinical features were analyzed and compared with the reported subjects. RESULTS In the proband, ES detected the novel NPRL3 frameshift variant (NM_001077350.3): c.151_152del (p.Thr51Glyfs*5). This variant is predicted to cause a loss of function and segregated in one affected brother. The review of 76 patients from 18 publications revealed the predominance of focal-onset seizures (67/74-90%), with mainly frontal and frontotemporal (32/67-47.7%), unspecified (19/67-28%), or temporal (9/67-13%) onset. Epileptic syndromes included familial focal epilepsy with variable foci (FFEVF) (29/74-39%) and SHE (11/74-14.9%). Fifteen patients out of 60 (25%) underwent epilepsy surgery, 11 of whom achieved complete seizure remission (11/15-73%). Focal cortical dysplasia (FCD) type 2A was the most frequent histopathological finding. SIGNIFICANCE We reported an illustrative NPRL3-related epilepsy (NRE) family with incomplete penetrance. This condition consists of a heterogeneous spectrum of clinical and neuroradiological features. Focal-onset motor seizures are predominant, and almost half of the cases fulfill the criteria for SHE or FFEVF. MRI-negative cases are prevalent, but the association with malformations of cortical developments (MCDs) is significant, especially FCD type 2a. The beneficial impact of epilepsy surgery in patients with MCD-related epilepsy further supports the inclusion of brain MRI in the workup of NRE patients.
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Affiliation(s)
- Alice Dainelli
- Pediatric Neurology and Muscular Diseases UnitIRCCS Istituto Giannina GasliniGenoaItaly
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child HealthUniversità Degli Studi di GenovaGenoaItaly
| | | | - Sara Rossato
- U.O.C. Pediatria, Ospedale San BortoloVicenzaItaly
| | | | - Monica Traverso
- Pediatric Neurology and Muscular Diseases UnitIRCCS Istituto Giannina GasliniGenoaItaly
| | | | | | - Valeria Capra
- UOC Genetica MedicaIRCCS Istituto Giannina GasliniGenoaItaly
| | - Marco Di Duca
- UOC Genetica MedicaIRCCS Istituto Giannina GasliniGenoaItaly
| | - Federico Zara
- UOC Genetica MedicaIRCCS Istituto Giannina GasliniGenoaItaly
| | - Marcello Scala
- Pediatric Neurology and Muscular Diseases UnitIRCCS Istituto Giannina GasliniGenoaItaly
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child HealthUniversità Degli Studi di GenovaGenoaItaly
| | - Pasquale Striano
- Pediatric Neurology and Muscular Diseases UnitIRCCS Istituto Giannina GasliniGenoaItaly
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child HealthUniversità Degli Studi di GenovaGenoaItaly
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2
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Nguyen LH, Sharma M, Bordey A. 4E-BP1 expression in embryonic postmitotic neurons mitigates mTORC1-induced cortical malformations and behavioral seizure severity but does not prevent epilepsy in mice. Front Neurosci 2023; 17:1257056. [PMID: 37680968 PMCID: PMC10480503 DOI: 10.3389/fnins.2023.1257056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 07/31/2023] [Indexed: 09/09/2023] Open
Abstract
Hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) pathway during neurodevelopment leads to focal cortical malformations associated with intractable seizures. Recent evidence suggests that dysregulated cap-dependent translation downstream of mTORC1 contributes to cytoarchitectural abnormalities and seizure activity. Here, we examined whether reducing cap-dependent translation by expressing a constitutively active form of the translational repressor, 4E-BP1, downstream of mTORC1 would prevent the development of cortical malformations and seizures. 4E-BP1CA was expressed embryonically either in radial glia (neural progenitor cells) that generate cortical layer 2/3 pyramidal neurons or in migrating neurons destined to layer 2/3 using a conditional expression system. In both conditions, 4E-BP1CA expression reduced mTORC1-induced neuronal hypertrophy and alleviated cortical mislamination, but a subset of ectopic neurons persisted in the deep layers and the white matter. Despite the above improvements, 4E-BP1CA expression in radial glia had no effects on seizure frequency and further exacerbated behavioral seizure severity associated with mTORC1 hyperactivation. In contrast, conditional 4E-BP1CA expression in migratory neurons mitigated the severity of behavioral seizures but the seizure frequency remained unchanged. These findings advise against targeting 4E-BPs by 4E-BP1CA expression during embryonic development for seizure prevention and suggest the presence of a development-dependent role for 4E-BPs in mTORC1-induced epilepsy.
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Affiliation(s)
- Lena H. Nguyen
- Department of Neuroscience, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, United States
- Departments of Neurosurgery and Cellular & Molecular Physiology, Wu Tsai Institute, Yale University School of Medicine, New Haven, CT, United States
| | - Manas Sharma
- Departments of Neurosurgery and Cellular & Molecular Physiology, Wu Tsai Institute, Yale University School of Medicine, New Haven, CT, United States
| | - Angelique Bordey
- Departments of Neurosurgery and Cellular & Molecular Physiology, Wu Tsai Institute, Yale University School of Medicine, New Haven, CT, United States
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3
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Gerasimenko A, Baldassari S, Baulac S. mTOR pathway: Insights into an established pathway for brain mosaicism in epilepsy. Neurobiol Dis 2023; 182:106144. [PMID: 37149062 DOI: 10.1016/j.nbd.2023.106144] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Revised: 05/02/2023] [Accepted: 05/03/2023] [Indexed: 05/08/2023] Open
Abstract
The mechanistic target of rapamycin (mTOR) signaling pathway is an essential regulator of numerous cellular activities such as metabolism, growth, proliferation, and survival. The mTOR cascade recently emerged as a critical player in the pathogenesis of focal epilepsies and cortical malformations. The 'mTORopathies' comprise a spectrum of cortical malformations that range from whole brain (megalencephaly) and hemispheric (hemimegalencephaly) abnormalities to focal abnormalities, such as focal cortical dysplasia type II (FCDII), which manifest with drug-resistant epilepsies. The spectrum of cortical dysplasia results from somatic brain mutations in the mTOR pathway activators AKT3, MTOR, PIK3CA, and RHEB and from germline and somatic mutations in mTOR pathway repressors, DEPDC5, NPRL2, NPRL3, TSC1 and TSC2. The mTORopathies are characterized by excessive mTOR pathway activation, leading to a broad range of structural and functional impairments. Here, we provide a comprehensive literature review of somatic mTOR-activating mutations linked to epilepsy and cortical malformations in 292 patients and discuss the perspectives of targeted therapeutics for personalized medicine.
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Affiliation(s)
- Anna Gerasimenko
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, Hôpital de la Pitié Salpêtrière, 75013 Paris, France; APHP Sorbonne Université, GH Pitié Salpêtrière et Trousseau, Département de Génétique, Centre de référence "déficiences intellectuelles de causes rares", Paris, France
| | - Sara Baldassari
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, Hôpital de la Pitié Salpêtrière, 75013 Paris, France
| | - Stéphanie Baulac
- Sorbonne Université, Institut du Cerveau - Paris Brain Institute - ICM, Inserm, CNRS, Hôpital de la Pitié Salpêtrière, 75013 Paris, France.
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4
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Lee WS, Macdonald-Laurs E, Stephenson SEM, D'Arcy C, MacGregor D, Leventer RJ, Maixner W, Harvey AS, Lockhart PJ. Basal ganglia dysplasia and mTORopathy: A potential cause of postoperative seizures in focal cortical dysplasia. Epilepsia Open 2023; 8:205-210. [PMID: 36461712 PMCID: PMC9977751 DOI: 10.1002/epi4.12678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 12/01/2022] [Indexed: 12/05/2022] Open
Abstract
Pathogenic somatic MTOR variants in the cerebral cortex are a frequent cause of focal cortical dysplasia (FCD). We describe a child with drug and surgery-resistant focal epilepsy due to FCD type II who developed progressive enlargement and T2 signal hyperintensity in the ipsilateral caudate and lentiform nuclei. Histopathology of caudate nucleus biopsies showed dysmorphic neurons, similar to those in resected cortex. Genetic analysis of frontal and temporal cortex and caudate nucleus identified a pathogenic somatic MTOR variant [NM_004958.4:c.4375G > C (p.Ala1459Pro)] that was not present in blood-derived gDNA. The mean variant allele frequency ranged from 0.4% to 3.2% in cerebral cortex and up to 5.4% in the caudate nucleus. The basal ganglia abnormalities suggest more widespread, potentially hemispheric dysplasia in this patient, consistent with the pathogenic variant occurring in early cerebral development. This finding provides a potential explanation for persistent seizures in some patients with seemingly complete resection of FCD or disconnection of a dysplastic hemisphere.
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Affiliation(s)
- Wei Shern Lee
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - Emma Macdonald-Laurs
- Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia.,Department of Neurology, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Sarah E M Stephenson
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
| | - Colleen D'Arcy
- Department of Anatomical Pathology, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Duncan MacGregor
- Department of Anatomical Pathology, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Richard J Leventer
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia.,Department of Neurology, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Wirginia Maixner
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia.,Department of Neurosurgery, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - A Simon Harvey
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia.,Department of Neurology, The Royal Children's Hospital, Parkville, Victoria, Australia
| | - Paul J Lockhart
- Murdoch Children's Research Institute, Parkville, Victoria, Australia.,Department of Paediatrics, The University of Melbourne, Parkville, Victoria, Australia
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5
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Wang Y, Yu T, Blümcke I, Cai Y, Sun K, Gao R, Wang Y, Fu Y, Wang W, Wang Y, Zhang G, Piao Y. The clinico-pathological characterisation of focal cortical dysplasia type IIb genetically defined by MTOR mosaicism. Neuropathol Appl Neurobiol 2023; 49:e12874. [PMID: 36544434 DOI: 10.1111/nan.12874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 08/18/2022] [Accepted: 10/11/2022] [Indexed: 12/24/2022]
Abstract
AIMS Focal cortical dysplasia (FCD) is a major cause of drug-resistant paediatric epilepsy and is amenable to successful neurosurgical resection. FCD ILAE Type IIb is the most common FCD subtype, and brain somatic mutations affecting the mTOR pathway play a major pathogenic role. The aim of this study was to comprehensively describe the genotype-phenotype association of 20 patients with histopathologically confirmed FCDIIb using next generation sequencing (NGS) of paired blood-brain samples. METHODS Clinical and neuropathological data were retrospectively reviewed from the hospital archive. The NGS panel included 11 mTOR-pathway-related genes with maximum coverage of 2000×. The detected variants were validated by digital droplet PCR. RESULTS Pathogenic MTOR variants were identified in 10 patients (50%). Further comparison with MTOR-wildtype FCDIIb suggested a profound genotype-phenotype association characterised by (1) a non-temporal lobe lesion on MRI, (2) a larger lesion volume occupying grey and white matter (3.032 ± 1.859 cm3 vs 1.110 ± 0.856 cm3 , p = 0.014), (3) more balloon cells (50.20 ± 14.40 BC/mm2 vs 31.64 ± 30.56 BC/mm2 , p = 0.099) and dysmorphic neurons (48.72 ± 19.47DN/mm2 vs 15.28 ± 13.95DN/mm2 , p = 0.000) and (4) a positive correlation between VAF and the lesion volume (r = 0.802, p = 0.017). CONCLUSIONS Our study identified frequent MTOR mutations in the cell-rich FCDIIb phenotype, clinically characterised by a non-temporal location and large lesion volume. Comprehensive genotype-phenotype associations will help us further explore and define the broad spectrum of FCD lesions to make more targeted therapies available in the realm of epileptology.
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Affiliation(s)
- Yajie Wang
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China
| | - Tao Yu
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.,Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Ingmar Blümcke
- Department of Neuropathology, University Hospital Erlangen, Erlangen, Germany
| | - Yanning Cai
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Department of Neurobiology and Clinical Biobank, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Ke Sun
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.,Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Runshi Gao
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.,Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yujiao Wang
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China
| | - Yongjuan Fu
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China
| | - Wei Wang
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yuping Wang
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Neuromodulation, Beijing, China.,Center of Epilepsy, Institute of Sleep and Consciousness Disorders, Beijing Institute for Brain Disorders, Capital Medical University, Beijing, China
| | - Guojun Zhang
- Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China.,Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.,Department of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yueshan Piao
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Clinical Research Center for Epilepsy, Capital Medical University, Beijing, China.,National Center for Neurological Disorders, Beijing, China
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6
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CfDNA Measurement as a Diagnostic Tool for the Detection of Brain Somatic Mutations in Refractory Epilepsy. Int J Mol Sci 2022; 23:ijms23094879. [PMID: 35563270 PMCID: PMC9102996 DOI: 10.3390/ijms23094879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/21/2022] [Accepted: 04/26/2022] [Indexed: 02/04/2023] Open
Abstract
Epilepsy is a neurological disorder that affects more than 50 million people. Its etiology is unknown in approximately 60% of cases, although the existence of a genetic factor is estimated in about 75% of these individuals. Hundreds of genes involved in epilepsy are known, and their number is increasing progressively, especially with next-generation sequencing techniques. However, there are still many cases in which the results of these molecular studies do not fully explain the phenotype of the patients. Somatic mutations specific to brain tissue could contribute to the phenotypic spectrum of epilepsy. Undetectable in the genomic DNA of blood cells, these alterations can be identified in cell-free DNA (cfDNA). We aim to review the current literature regarding the detection of somatic variants in cfDNA to diagnose refractory epilepsy, highlighting novel research directions and suggesting further studies.
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7
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Coleman N, Subbiah V, Pant S, Patel K, Roy-Chowdhuri S, Yedururi S, Johnson A, Yap TA, Rodon J, Shaw K, Meric-Bernstam F. Emergence of mTOR mutation as an acquired resistance mechanism to AKT inhibition, and subsequent response to mTORC1/2 inhibition. NPJ Precis Oncol 2021; 5:99. [PMID: 34853384 PMCID: PMC8636467 DOI: 10.1038/s41698-021-00240-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 11/09/2021] [Indexed: 01/14/2023] Open
Abstract
Acquired resistance to molecular targeted therapy is a significant challenge of the precision medicine era. The ability to understand these mechanisms of resistance may improve patient selection and allow for the development of rationally designed next-line or combination treatment strategies and improved patient outcomes. AKT is a critical effector of the phosphoinositide 3-kinase signaling cascade, one of the most commonly activated pathways in human cancer. Deregulation of signaling pathways, such as RAF/MEK/ERK are previously described mechanisms of resistance to AKT/PI3K inhibitors. Mutations in the mTOR gene, however, are exceedingly rare. We present a case of acquired mTOR resistance, following targeted AKT inhibition, and subsequent response to mTOR1/2 inhibitor in a patient with metastatic endometrial cancer, the first documented response to ATP-competitive mTOR inhibition in this setting. This case supports mTOR mutation as a mechanism of resistance, and underscores the importance of tumor molecular profiling, exemplifying precision medicine in action.
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Affiliation(s)
- Niamh Coleman
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA
| | - Vivek Subbiah
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA
| | - Shubham Pant
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA
| | - Keyur Patel
- Khalifa Institute for Personalized Cancer Therapy, MD Anderson Cancer Center, Houston, TX, USA
| | | | - Sireesha Yedururi
- Abdominal Imaging Department, MD Anderson Cancer Center, Houston, TX, USA
| | - Amber Johnson
- Khalifa Institute for Personalized Cancer Therapy, MD Anderson Cancer Center, Houston, TX, USA
| | - Timothy A Yap
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA
- Khalifa Institute for Personalized Cancer Therapy, MD Anderson Cancer Center, Houston, TX, USA
| | - Jordi Rodon
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA
| | - Kenna Shaw
- Khalifa Institute for Personalized Cancer Therapy, MD Anderson Cancer Center, Houston, TX, USA
| | - Funda Meric-Bernstam
- Department of Investigational Cancer Therapeutics (Phase I Program), The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX, 77030, USA.
- Khalifa Institute for Personalized Cancer Therapy, MD Anderson Cancer Center, Houston, TX, USA.
- Department of Surgical Oncology, MD Anderson Cancer Center, Houston, TX, USA.
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8
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Nguyen LH, Xu Y, Mahadeo T, Zhang L, Lin TV, Born HA, Anderson AE, Bordey A. Expression of 4E-BP1 in juvenile mice alleviates mTOR-induced neuronal dysfunction and epilepsy. Brain 2021; 145:1310-1325. [PMID: 34849602 DOI: 10.1093/brain/awab390] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/01/2021] [Accepted: 09/22/2021] [Indexed: 11/13/2022] Open
Abstract
Hyperactivation of the mechanistic target of rapamycin (mTOR) pathway during fetal neurodevelopment alters neuron structure and function, leading to focal malformation of cortical development (FMCD) and intractable epilepsy. Recent evidence suggests a role for dysregulated cap-dependent translation downstream of mTOR in the formation of FMCD and seizures. However, it is unknown whether modifying translation once the developmental pathologies are established can reverse neuronal abnormalities and seizures. Addressing these issues is crucial with regards to therapeutics since these neurodevelopmental disorders are predominantly diagnosed during childhood, when patients present with symptoms. Here, we report increased phosphorylation of the mTOR effector and translational repressor, 4E-BP1, in patient FMCD tissue and in a mouse model of FMCD. Using temporally regulated conditional gene expression systems, we found that expression of a constitutively active form of 4E-BP1 that resists phosphorylation by mTOR in juvenile mice reduced neuronal cytomegaly and corrected several neuronal electrophysiological alterations, including depolarized resting membrane potential, irregular firing pattern, and aberrant expression of HCN4 channels. Further, 4E-BP1 expression in juvenile FMCD mice after epilepsy onset resulted in improved cortical spectral activity and decreased spontaneous seizure frequency in adults. Overall, our study uncovered a remarkable plasticity of the juvenile brain that facilitates novel therapeutic opportunities to treat FMCD-related epilepsy during childhood with potentially long-lasting effects in adults.
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Affiliation(s)
- Lena H Nguyen
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA.,Department of Cellular and Molecular Physiology, Yale University School of Medicine; New Haven, CT 06510, USA
| | - Youfen Xu
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA
| | - Travorn Mahadeo
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA
| | - Longbo Zhang
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA
| | - Tiffany V Lin
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA
| | - Heather A Born
- Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital; Houston, TX 77030, USA.,Department of Pediatrics, Baylor College of Medicine; Houston, TX 77030, USA
| | - Anne E Anderson
- Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital; Houston, TX 77030, USA.,Department of Pediatrics, Baylor College of Medicine; Houston, TX 77030, USA
| | - Angélique Bordey
- Department of Neurosurgery, Yale University School of Medicine; New Haven, CT 06510, USA.,Department of Cellular and Molecular Physiology, Yale University School of Medicine; New Haven, CT 06510, USA
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9
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Vasic V, Jones MSO, Haslinger D, Knaus LS, Schmeisser MJ, Novarino G, Chiocchetti AG. Translating the Role of mTOR- and RAS-Associated Signalopathies in Autism Spectrum Disorder: Models, Mechanisms and Treatment. Genes (Basel) 2021; 12:genes12111746. [PMID: 34828352 PMCID: PMC8624393 DOI: 10.3390/genes12111746] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/25/2021] [Accepted: 10/28/2021] [Indexed: 12/23/2022] Open
Abstract
Mutations affecting mTOR or RAS signaling underlie defined syndromes (the so-called mTORopathies and RASopathies) with high risk for Autism Spectrum Disorder (ASD). These syndromes show a broad variety of somatic phenotypes including cancers, skin abnormalities, heart disease and facial dysmorphisms. Less well studied are the neuropsychiatric symptoms such as ASD. Here, we assess the relevance of these signalopathies in ASD reviewing genetic, human cell model, rodent studies and clinical trials. We conclude that signalopathies have an increased liability for ASD and that, in particular, ASD individuals with dysmorphic features and intellectual disability (ID) have a higher chance for disruptive mutations in RAS- and mTOR-related genes. Studies on rodent and human cell models confirm aberrant neuronal development as the underlying pathology. Human studies further suggest that multiple hits are necessary to induce the respective phenotypes. Recent clinical trials do only report improvements for comorbid conditions such as epilepsy or cancer but not for behavioral aspects. Animal models show that treatment during early development can rescue behavioral phenotypes. Taken together, we suggest investigating the differential roles of mTOR and RAS signaling in both human and rodent models, and to test drug treatment both during and after neuronal development in the available model systems.
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Affiliation(s)
- Verica Vasic
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany; (V.V.); (M.J.S.)
| | - Mattson S. O. Jones
- Autism Therapy and Research Center of Excellence, Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University Hospital Frankfurt, 60528 Frankfurt am Main, Germany; (M.S.O.J.); (D.H.)
- Center for Personalized Translational Epilepsy Research (CePTER), Goethe University Frankfurt, 60528 Frankfurt am Main, Germany
| | - Denise Haslinger
- Autism Therapy and Research Center of Excellence, Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University Hospital Frankfurt, 60528 Frankfurt am Main, Germany; (M.S.O.J.); (D.H.)
- Institute of Science and Technology (IST) Austria, 3400 Klosterneuburg, Austria; (L.S.K.); (G.N.)
| | - Lisa S. Knaus
- Institute of Science and Technology (IST) Austria, 3400 Klosterneuburg, Austria; (L.S.K.); (G.N.)
| | - Michael J. Schmeisser
- Institute for Microscopic Anatomy and Neurobiology, University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany; (V.V.); (M.J.S.)
- Focus Program Translational Neurosciences (FTN), University Medical Center of the Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Gaia Novarino
- Institute of Science and Technology (IST) Austria, 3400 Klosterneuburg, Austria; (L.S.K.); (G.N.)
| | - Andreas G. Chiocchetti
- Autism Therapy and Research Center of Excellence, Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University Hospital Frankfurt, 60528 Frankfurt am Main, Germany; (M.S.O.J.); (D.H.)
- Center for Personalized Translational Epilepsy Research (CePTER), Goethe University Frankfurt, 60528 Frankfurt am Main, Germany
- Correspondence: ; Tel.: +49-69-6301-80658
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10
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Nguyen LH, Bordey A. Corrigendum: Convergent and Divergent Mechanisms of Epileptogenesis in mTORopathies. Front Neuroanat 2021; 15:715363. [PMID: 34295225 PMCID: PMC8290855 DOI: 10.3389/fnana.2021.715363] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 05/28/2021] [Indexed: 01/16/2023] Open
Affiliation(s)
- Lena H Nguyen
- Department of Neurosurgery, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Cellular & Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Angélique Bordey
- Department of Neurosurgery, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Cellular & Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
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11
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Proietti Onori M, Koene LMC, Schäfer CB, Nellist M, de Brito van Velze M, Gao Z, Elgersma Y, van Woerden GM. RHEB/mTOR hyperactivity causes cortical malformations and epileptic seizures through increased axonal connectivity. PLoS Biol 2021; 19:e3001279. [PMID: 34038402 PMCID: PMC8186814 DOI: 10.1371/journal.pbio.3001279] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 06/08/2021] [Accepted: 05/10/2021] [Indexed: 01/03/2023] Open
Abstract
Hyperactivation of the mammalian target of rapamycin (mTOR) pathway can cause malformation of cortical development (MCD) with associated epilepsy and intellectual disability (ID) through a yet unknown mechanism. Here, we made use of the recently identified dominant-active mutation in Ras Homolog Enriched in Brain 1 (RHEB), RHEBp.P37L, to gain insight in the mechanism underlying the epilepsy caused by hyperactivation of the mTOR pathway. Focal expression of RHEBp.P37L in mouse somatosensory cortex (SScx) results in an MCD-like phenotype, with increased mTOR signaling, ectopic localization of neurons, and reliable generalized seizures. We show that in this model, the mTOR-dependent seizures are caused by enhanced axonal connectivity, causing hyperexcitability of distally connected neurons. Indeed, blocking axonal vesicle release from the RHEBp.P37L neurons alone completely stopped the seizures and normalized the hyperexcitability of the distally connected neurons. These results provide new evidence of the extent of anatomical and physiological abnormalities caused by mTOR hyperactivity, beyond local malformations, which can lead to generalized epilepsy. Hyperactivation of the mTOR pathway can cause cortical malformations and epilepsy. This study reveals that these effects can be uncoupled and that mTOR hyperactivity in a limited set of neurons induces hyperexcitability in non-targeted, healthy neurons, suggesting that it is actually these changes that may underlie mTOR-driven epileptogenesis.
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Affiliation(s)
- Martina Proietti Onori
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
- The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Linda M. C. Koene
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
- The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Carmen B. Schäfer
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Mark Nellist
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, Zuid Holland, the Netherlands
| | | | - Zhenyu Gao
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Ype Elgersma
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
- The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus Medical Center, Rotterdam, the Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, Zuid Holland, the Netherlands
- * E-mail: (YE); (GMvW)
| | - Geeske M. van Woerden
- Department of Neuroscience, Erasmus Medical Center, Rotterdam, the Netherlands
- The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus Medical Center, Rotterdam, the Netherlands
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, Zuid Holland, the Netherlands
- * E-mail: (YE); (GMvW)
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12
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Nguyen LH, Bordey A. Convergent and Divergent Mechanisms of Epileptogenesis in mTORopathies. Front Neuroanat 2021; 15:664695. [PMID: 33897381 PMCID: PMC8064518 DOI: 10.3389/fnana.2021.664695] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 03/17/2021] [Indexed: 12/30/2022] Open
Abstract
Hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1) due to mutations in genes along the PI3K-mTOR pathway and the GATOR1 complex causes a spectrum of neurodevelopmental disorders (termed mTORopathies) associated with malformation of cortical development and intractable epilepsy. Despite these gene variants’ converging impact on mTORC1 activity, emerging findings suggest that these variants contribute to epilepsy through both mTORC1-dependent and -independent mechanisms. Here, we review the literature on in utero electroporation-based animal models of mTORopathies, which recapitulate the brain mosaic pattern of mTORC1 hyperactivity, and compare the effects of distinct PI3K-mTOR pathway and GATOR1 complex gene variants on cortical development and epilepsy. We report the outcomes on cortical pyramidal neuronal placement, morphology, and electrophysiological phenotypes, and discuss some of the converging and diverging mechanisms responsible for these alterations and their contribution to epileptogenesis. We also discuss potential therapeutic strategies for epilepsy, beyond mTORC1 inhibition with rapamycin or everolimus, that could offer personalized medicine based on the gene variant.
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Affiliation(s)
- Lena H Nguyen
- Department of Neurosurgery, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Cellular & Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
| | - Angélique Bordey
- Department of Neurosurgery, Yale School of Medicine, Yale University, New Haven, CT, United States.,Department of Cellular & Molecular Physiology, Yale School of Medicine, Yale University, New Haven, CT, United States
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13
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Lee WS, Stephenson SEM, Pope K, Gillies G, Maixner W, Macdonald-Laurs E, MacGregor D, D'Arcy C, Jackson G, Harvey AS, Leventer RJ, Lockhart PJ. Genetic characterization identifies bottom-of-sulcus dysplasia as an mTORopathy. Neurology 2020; 95:e2542-e2551. [PMID: 32847954 DOI: 10.1212/wnl.0000000000010670] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 06/03/2020] [Indexed: 01/16/2023] Open
Abstract
OBJECTIVE To determine the genetic basis of bottom-of-sulcus dysplasia (BOSD), which is a highly focal and epileptogenic cortical malformation in which the imaging, electrophysiologic, and pathologic abnormalities are maximal at the bottom of sulcus, tapering to a normal gyral crown. METHODS Targeted panel deep sequencing (>500×) was performed on paired blood and brain-derived genomic DNA from 20 operated patients with drug-resistant focal epilepsy and BOSD. Histopathology was assessed using immunohistochemistry. RESULTS Brain-specific pathogenic somatic variants were found in 6 patients and heterozygous pathogenic germline variants were found in 2. Somatic variants were identified in MTOR and germline variants were identified in DEPDC5 and NPRL3. Two patients with somatic MTOR variants showed a mutation gradient, with higher mutation load at the bottom of sulcus compared to the gyral crown. Immunohistochemistry revealed an abundance of dysmorphic neurons and balloon cells in the bottom of sulcus but not in the gyral crown or adjacent gyri. CONCLUSIONS BOSD is associated with mTOR pathway dysregulation and shares common genetic etiologies and pathogenic mechanisms with other forms of focal and hemispheric cortical dysplasia, suggesting these disorders are on a genetic continuum.
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Affiliation(s)
- Wei Shern Lee
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Sarah E M Stephenson
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Kate Pope
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Greta Gillies
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Wirginia Maixner
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Emma Macdonald-Laurs
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Duncan MacGregor
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Colleen D'Arcy
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Graeme Jackson
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - A Simon Harvey
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Richard J Leventer
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - Paul J Lockhart
- From the Bruce Lefroy Centre (W.S.L., S.E.M.S., K.P., G.G., P.J.L.), Murdoch Children's Research Institute (W.M., A.S.H., R.J.L.); Department of Paediatrics (W.S.L., S.E.M.S., W.M., E.M.-L., A.S.H., R.J.L., P.J.L.), The University of Melbourne; Departments of Neurosurgery (W.M.), Neurology (E.M.-L., A.S.H., R.J.L.), and Anatomical Pathology (D.M., C.D.), The Royal Children's Hospital, Parkville; and Melbourne Brain Centre (G.J.), The Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia.
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14
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Feliciano DM. The Neurodevelopmental Pathogenesis of Tuberous Sclerosis Complex (TSC). Front Neuroanat 2020; 14:39. [PMID: 32765227 PMCID: PMC7381175 DOI: 10.3389/fnana.2020.00039] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/10/2020] [Indexed: 12/22/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a model disorder for understanding brain development because the genes that cause TSC are known, many downstream molecular pathways have been identified, and the resulting perturbations of cellular events are established. TSC, therefore, provides an intellectual framework to understand the molecular and biochemical pathways that orchestrate normal brain development. The TSC1 and TSC2 genes encode Hamartin and Tuberin which form a GTPase activating protein (GAP) complex. Inactivating mutations in TSC genes (TSC1/TSC2) cause sustained Ras homologue enriched in brain (RHEB) activation of the mammalian isoform of the target of rapamycin complex 1 (mTORC1). TOR is a protein kinase that regulates cell size in many organisms throughout nature. mTORC1 inhibits catabolic processes including autophagy and activates anabolic processes including mRNA translation. mTORC1 regulation is achieved through two main upstream mechanisms. The first mechanism is regulation by growth factor signaling. The second mechanism is regulation by amino acids. Gene mutations that cause too much or too little mTORC1 activity lead to a spectrum of neuroanatomical changes ranging from altered brain size (micro and macrocephaly) to cortical malformations to Type I neoplasias. Because somatic mutations often underlie these changes, the timing, and location of mutation results in focal brain malformations. These mutations, therefore, provide gain-of-function and loss-of-function changes that are a powerful tool to assess the events that have gone awry during development and to determine their functional physiological consequences. Knowledge about the TSC-mTORC1 pathway has allowed scientists to predict which upstream and downstream mutations should cause commensurate neuroanatomical changes. Indeed, many of these predictions have now been clinically validated. A description of clinical imaging and histochemical findings is provided in relation to laboratory models of TSC that will allow the reader to appreciate how human pathology can provide an understanding of the fundamental mechanisms of development.
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Affiliation(s)
- David M Feliciano
- Department of Biological Sciences, Clemson University, Clemson, SC, United States
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15
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Tarkowski B, Kuchcinska K, Blazejczyk M, Jaworski J. Pathological mTOR mutations impact cortical development. Hum Mol Genet 2020; 28:2107-2119. [PMID: 30789219 DOI: 10.1093/hmg/ddz042] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/08/2019] [Accepted: 02/11/2019] [Indexed: 02/03/2023] Open
Abstract
Several mosaic mutations of the mammalian/mechanistic target of rapamycin (mTOR) have recently been found in patients with cortical malformations, such as hemimegalencephaly (HME) and focal cortical dysplasia (FCD). Although all of them should activate mTOR signaling, comparisons of the impact of different mTOR mutations on brain development have been lacking. Also it remains unknown if any potential differences these mutations may have on cortical development are directly related to a degree of mTOR signaling increase. The present study assessed levels of mTORC1 pathway activity in cell lines and rat primary neurons overexpressing several mTOR mutants that were previously found in HME, FCD, cancer patients and in vitro mutagenesis screens. Next we introduced the mutants, enhancing mTORC1 signaling most potently, into developing mouse brains and assessed electroporated cell morphology and migratory phenotype using immunofluorescent staining. We observed the differential inhibition of neuronal progenitor cortical migration, which partly corresponded with a degree of mTORC1 signaling enhancement these mutants induced in cultured cells. The most potent quadruple mutant prevented most of the progenitors from entering the cortical plate. Cells that expressed less potent, single-point, mTOR mutants entered the cortical plate but failed to reach its upper layers and had enlarged soma. Our findings suggest a correlation between the potency of mTOR mutation to activate mTORC1 pathway and disruption of cortical migration.
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Affiliation(s)
- Bartosz Tarkowski
- International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Kinga Kuchcinska
- International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Jacek Jaworski
- International Institute of Molecular and Cell Biology, Warsaw, Poland
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16
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A novel de novo MTOR gain-of-function variant in a patient with Smith-Kingsmore syndrome and Antiphospholipid syndrome. Eur J Hum Genet 2019; 27:1369-1378. [PMID: 31053780 DOI: 10.1038/s41431-019-0418-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 03/21/2019] [Accepted: 04/16/2019] [Indexed: 01/22/2023] Open
Abstract
We report the clinical, biochemical and genetic findings from a Spanish girl of Caucasian origin who presented with macrocephaly, dysmorphic facial features, developmental delay, hypotonia, combined oxidative phosphorylation (OxPhos) deficiency, epilepsy and anti-phospholipid antibodies (aPL). Whole-exome sequencing (WES) uncovered a heterozygous variant in the MTOR gene (NM_004958.3: c.7235A>T: p.(Asp2412Val)) that encodes for the Serine/threonine-protein kinase mTOR. The substrates phosphorylation experiments demonstrated that this variant exerts its effect by gain-of-function (GOF) and autosomal dominant mechanism. GOF variants in this protein have been associated with Smith-Kingsmore syndrome (SKS), a rare autosomal dominant disorder characterized by intellectual disability, macrocephaly, seizure, developmental delay and dysmorphic facial features. Furthermore, the mTOR pathway has been demonstrated previously to be involved in many types of endothelium injuries including the antiphospholipid syndrome (APS), a systemic autoimmune disease characterized by the production of aPL with recurrent vascular thrombosis. Therefore, our patient is the first one with an mTOR variant and diagnosed with SKS and APS. In conclusion, our data expand both the genetic and phenotypic spectrum associated with MTOR gene variants.
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17
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Xu Q, Uliel-Sibony S, Dunham C, Sarnat H, Flores-Sarnat L, Brunga L, Davidson S, Lo W, Shlien A, Connolly M, Boelman C, Datta A. mTOR Inhibitors as a New Therapeutic Strategy in Treatment Resistant Epilepsy in Hemimegalencephaly: A Case Report. J Child Neurol 2019; 34:132-138. [PMID: 30514132 DOI: 10.1177/0883073818813238] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Hemimegalencephaly is a hamartomatous malformation of one hemisphere. Functional hemispherectomy, the definitive treatment, is associated with significant morbidity and mortality in early infancy. Dysregulation of the mTOR pathway can result in malformations of cortical development, and mTOR inhibitors can effectively reduce seizures in tuberous sclerosis complex. We report a 6-day-old female with hemimegalencephaly and frequent seizures despite 9 antiseizure medications. At 3 months of age, while awaiting hemispherectomy, an mTOR inhibitor, rapamycin, was initiated by the neurologist. After 1 week of treatment, there was >50% reduction in seizures and total seizure burden, and after 2 weeks, development improved, resulting in deferral of surgery by 2.5 months with an increased body weight. Pathology demonstrated cortical dysplasia with upregulation of the mTOR pathway. Deep-sequencing of brain tissue demonstrated 16% mosaicism for a pathogenic de novo MTOR gene mutation. This case exemplifies how mTOR inhibitors could be considered for seizure reduction in patients with hemimegalencephaly while awaiting surgery.
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Affiliation(s)
- Qi Xu
- 1 Division of Neurology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
| | - Shimrit Uliel-Sibony
- 1 Division of Neurology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
| | - Christopher Dunham
- 2 Department of Pathology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
| | - Harvey Sarnat
- 3 Division of Pediatric Neurology, University of Calgary, Alberta Children's Hospital, Calgary, AB, Canada
| | - Laura Flores-Sarnat
- 3 Division of Pediatric Neurology, University of Calgary, Alberta Children's Hospital, Calgary, AB, Canada
| | - Ledia Brunga
- 4 University of Toronto, Program in Genetics and Genome Biology, the Hospital for Sick Children, Toronto, ON, Canada
| | - Scott Davidson
- 4 University of Toronto, Program in Genetics and Genome Biology, the Hospital for Sick Children, Toronto, ON, Canada
| | - Winnie Lo
- 4 University of Toronto, Program in Genetics and Genome Biology, the Hospital for Sick Children, Toronto, ON, Canada
| | - Adam Shlien
- 4 University of Toronto, Program in Genetics and Genome Biology, the Hospital for Sick Children, Toronto, ON, Canada
| | - Mary Connolly
- 1 Division of Neurology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
| | - Cyrus Boelman
- 1 Division of Neurology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
| | - Anita Datta
- 1 Division of Neurology, University of British Columbia, BC Children's Hospital, Vancouver, BC, Canada
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18
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Lu DS, Karas PJ, Krueger DA, Weiner HL. Central nervous system manifestations of tuberous sclerosis complex. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2018; 178:291-298. [PMID: 30230171 DOI: 10.1002/ajmg.c.31647] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/28/2018] [Accepted: 06/30/2018] [Indexed: 01/21/2023]
Abstract
Tuberous sclerosis complex (TSC) is a neurocutaneous autosomal-dominant genetic syndrome marked by development of hamartomatous lesions arising from dysfunction of the mammalian target of rapamycin (mTOR) pathway. Although TSC remains a heterogeneous clinical entity, the recent inclusion of genetic diagnostic criteria reflects advancement in our understanding of its underlying etiopathogenesis. Abnormal cellular growth, differentiation, and migration result in multisystem sequelae, with neurologic manifestations of TSC representing the primary cause of morbidity and mortality for the majority of individuals. Modern imaging techniques aid in the diagnosis of TSC and guide treatment strategies by revealing central nervous system findings. Cortical tubers are the namesake lesion of the disorder and occur in up to 90% of cases, often exerting significant epileptogenic potential. Subependymal nodules are found in 80% of patients as calcified tumors lining the ependyma of the lateral ventricles. In some cases, these nodules are thought to progress to subependymal giant cell astrocytomas and may present with obstructive hydrocephalus. Retinal astrocytic hamartomas are also common, present in 50% of patients. Surgery remains the treatment of choice for large or symptomatic lesions, though clinical trials have highlighted a potential role for mTOR pathway antagonism. A multidisciplinary approach is necessary for achieving optimal patient outcomes.
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Affiliation(s)
- Derek S Lu
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas
| | - Patrick J Karas
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas
| | - Darcy A Krueger
- Division of Child Neurology, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Howard L Weiner
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas.,Division of Pediatric Neurosurgery, Department of Surgery, Texas Children's Hospital, Houston, Texas
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19
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Zucco AJ, Pozzo VD, Afinogenova A, Hart RP, Devinsky O, D'Arcangelo G. Neural progenitors derived from Tuberous Sclerosis Complex patients exhibit attenuated PI3K/AKT signaling and delayed neuronal differentiation. Mol Cell Neurosci 2018; 92:149-163. [PMID: 30144504 DOI: 10.1016/j.mcn.2018.08.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 07/23/2018] [Accepted: 08/20/2018] [Indexed: 12/20/2022] Open
Abstract
Tuberous Sclerosis Complex (TSC) is a disease caused by autosomal dominant mutations in the TSC1 or TSC2 genes, and is characterized by tumor susceptibility, brain lesions, seizures and behavioral impairments. The TSC1 and TSC2 genes encode proteins forming a complex (TSC), which is a major regulator and suppressor of mammalian target of rapamycin complex 1 (mTORC1), a signaling complex that promotes cell growth and proliferation. TSC1/2 loss of heterozygosity (LOH) and the subsequent complete loss of TSC regulatory activity in null cells causes mTORC1 dysregulation and TSC-associated brain lesions or other tissue tumors. However, it is not clear whether TSC1/2 heterozygous brain cells are abnormal and contribute to TSC neuropathology. To investigate this issue, we generated induced pluripotent stem cells (iPSCs) from TSC patients and unaffected controls, and utilized these to obtain neural progenitor cells (NPCs) and differentiated neurons in vitro. These patient-derived TSC2 heterozygous NPCs were delayed in their ability to differentiate into neurons. Patient-derived progenitor cells also exhibited a modest activation of mTORC1 signaling downstream of TSC, and a marked attenuation of upstream PI3K/AKT signaling. We further show that pharmacologic PI3K or AKT inhibition, but not mTORC1 inhibition, causes a neuronal differentiation delay, mimicking the patient phenotype. Together these data suggest that heterozygous TSC2 mutations disrupt neuronal development, potentially contributing to the disease neuropathology, and that this defect may result from dysregulated PI3K/AKT signaling in neural progenitor cells.
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Affiliation(s)
- Avery J Zucco
- Graduate Program in Neuroscience, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, United States of America; Department of Cell Biology and Neuroscience, Rutgers, the State University of New Jersey, Piscataway, NJ, United States of America
| | - Valentina Dal Pozzo
- Graduate Program in Neuroscience, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ, United States of America; Department of Cell Biology and Neuroscience, Rutgers, the State University of New Jersey, Piscataway, NJ, United States of America
| | - Alina Afinogenova
- Department of Cell Biology and Neuroscience, Rutgers, the State University of New Jersey, Piscataway, NJ, United States of America
| | - Ronald P Hart
- Department of Cell Biology and Neuroscience, Rutgers, the State University of New Jersey, Piscataway, NJ, United States of America; Human Genetics Institute of New Jersey, Piscataway, NJ, United States of America
| | - Orrin Devinsky
- NYU Comprehensive Epilepsy Center, NYU Langone School of Medicine, New York, NY, United States of America
| | - Gabriella D'Arcangelo
- Department of Cell Biology and Neuroscience, Rutgers, the State University of New Jersey, Piscataway, NJ, United States of America; Human Genetics Institute of New Jersey, Piscataway, NJ, United States of America.
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20
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MTOR pathway in focal cortical dysplasia type 2: What do we know? Epilepsy Behav 2018; 85:157-163. [PMID: 29945038 DOI: 10.1016/j.yebeh.2018.05.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/08/2018] [Accepted: 05/09/2018] [Indexed: 01/15/2023]
Abstract
Focal cortical dysplasia (FCD) is the most commonly encountered developmental malformation that causes refractory epilepsy. Focal cortical dysplasia type 2 is one of the most usual neuropathological findings in tissues resected therapeutically from patients with drug-resistant epilepsy. Unlike other types of FCD, it is characterized by laminar disorganization and dysplastic neurons, which compromise the organization of the six histologically known layers in the cortex; the morphology and/or cell location can also be altered. A comprehensive review about the pathogenesis of this disease is important because of the necessity to update the results reported over the past years. Here, we present an updated review through Pubmed about the mammalian target of rapamycin (MTOR) pathway in FCD type 2. A wide variety of aspects was covered in 44 articles related to molecular and cellular biology, including experiments in animal and human models. The first publications appeared in 2004, but there is still a lack of studies specifically for one type of FCD. With the advancement of techniques and greater access to molecular and cellular experiments, such as induced pluripotent stem cells (iPSCs) and organoids, it is believed that the trend is increasing the number of publications contributing to the achievement of new discoveries.
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21
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Reijnders MRF, Kousi M, van Woerden GM, Klein M, Bralten J, Mancini GMS, van Essen T, Proietti-Onori M, Smeets EEJ, van Gastel M, Stegmann APA, Stevens SJC, Lelieveld SH, Gilissen C, Pfundt R, Tan PL, Kleefstra T, Franke B, Elgersma Y, Katsanis N, Brunner HG. Variation in a range of mTOR-related genes associates with intracranial volume and intellectual disability. Nat Commun 2017; 8:1052. [PMID: 29051493 PMCID: PMC5648772 DOI: 10.1038/s41467-017-00933-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Accepted: 08/08/2017] [Indexed: 11/09/2022] Open
Abstract
De novo mutations in specific mTOR pathway genes cause brain overgrowth in the context of intellectual disability (ID). By analyzing 101 mMTOR-related genes in a large ID patient cohort and two independent population cohorts, we show that these genes modulate brain growth in health and disease. We report the mTOR activator gene RHEB as an ID gene that is associated with megalencephaly when mutated. Functional testing of mutant RHEB in vertebrate animal models indicates pathway hyperactivation with a concomitant increase in cell and head size, aberrant neuronal migration, and induction of seizures, concordant with the human phenotype. This study reveals that tight control of brain volume is exerted through a large community of mTOR-related genes. Human brain volume can be altered, by either rare disruptive events causing hyperactivation of the pathway, or through the collective effects of common alleles.
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Affiliation(s)
- M R F Reijnders
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - M Kousi
- Center for Human Disease Modeling, Duke University, Durham, NC, 27701, USA
| | - G M van Woerden
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, 3015 CN, Rotterdam, The Netherlands
| | - M Klein
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - J Bralten
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - G M S Mancini
- Department of Clinical Genetics, Erasmus MC, Sophia Children's Hospital, 3000 CA, Rotterdam, The Netherlands
| | - T van Essen
- Department of Genetics, University of Groningen, University Medical Center of Groningen, 9700 RB, Groningen, The Netherlands
| | - M Proietti-Onori
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, 3015 CN, Rotterdam, The Netherlands
| | - E E J Smeets
- Department of Clinical Genetics and School for Oncology & Developmental Biology (GROW), Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands
| | - M van Gastel
- Department of Medical Care, SWZ zorg, 5691 AG, Son, The Netherlands
| | - A P A Stegmann
- Department of Clinical Genetics and School for Oncology & Developmental Biology (GROW), Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands
| | - S J C Stevens
- Department of Clinical Genetics and School for Oncology & Developmental Biology (GROW), Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands
| | - S H Lelieveld
- Department of Human Genetics, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, 6500 GA, Nijmegen, The Netherlands
| | - C Gilissen
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - R Pfundt
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - P L Tan
- Center for Human Disease Modeling, Duke University, Durham, NC, 27701, USA
| | - T Kleefstra
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands
| | - B Franke
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands.,Department of Psychiatry, Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6500 GA, Nijmegen, The Netherlands
| | - Y Elgersma
- Department of Neuroscience and ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus University Medical Center, 3015 CN, Rotterdam, The Netherlands
| | - N Katsanis
- Center for Human Disease Modeling, Duke University, Durham, NC, 27701, USA
| | - H G Brunner
- Department of Human Genetics, Radboud University Medical Center, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, 6500 GA, The Netherlands. .,Department of Clinical Genetics and School for Oncology & Developmental Biology (GROW), Maastricht University Medical Center, 6202 AZ, Maastricht, The Netherlands.
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