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Man A, Di Scipio M, Grewal S, Suk Y, Trinari E, Ejaz R, Whitney R. The Genetics of Tuberous Sclerosis Complex and Related mTORopathies: Current Understanding and Future Directions. Genes (Basel) 2024; 15:332. [PMID: 38540392 PMCID: PMC10970281 DOI: 10.3390/genes15030332] [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: 02/12/2024] [Revised: 03/02/2024] [Accepted: 03/02/2024] [Indexed: 06/14/2024] Open
Abstract
The mechanistic target of rapamycin (mTOR) pathway serves as a master regulator of cell growth, proliferation, and survival. Upregulation of the mTOR pathway has been shown to cause malformations of cortical development, medically refractory epilepsies, and neurodevelopmental disorders, collectively described as mTORopathies. Tuberous sclerosis complex (TSC) serves as the prototypical mTORopathy. Characterized by the development of benign tumors in multiple organs, pathogenic variants in TSC1 or TSC2 disrupt the TSC protein complex, a negative regulator of the mTOR pathway. Variants in critical domains of the TSC complex, especially in the catalytic TSC2 subunit, correlate with increased disease severity. Variants in less crucial exons and non-coding regions, as well as those undetectable with conventional testing, may lead to milder phenotypes. Despite the assumption of complete penetrance, expressivity varies within families, and certain variants delay disease onset with milder neurological effects. Understanding these genotype-phenotype correlations is crucial for effective clinical management. Notably, 15% of patients have no mutation identified by conventional genetic testing, with the majority of cases postulated to be caused by somatic TSC1/TSC2 variants which present complex diagnostic challenges. Advancements in genetic testing, prenatal screening, and precision medicine hold promise for changing the diagnostic and treatment paradigm for TSC and related mTORopathies. Herein, we explore the genetic and molecular mechanisms of TSC and other mTORopathies, emphasizing contemporary genetic methods in understanding and diagnosing the condition.
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Affiliation(s)
- Alice Man
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Matteo Di Scipio
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Shan Grewal
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Yujin Suk
- Michael G. DeGroote School of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Elisabetta Trinari
- Division of Developmental Pediatrics, Department of Pediatrics, McMaster Children’s Hospital, Hamilton, ON L8N 3Z5, Canada
| | - Resham Ejaz
- Division of Genetics, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4L8, Canada
| | - Robyn Whitney
- Division of Neurology, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4L8, Canada
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Ancora C, Marchi M, Bonardi CM, Sartori G, Lopreiato R, Zuccarello D, D'Errico I, Nosadini M, Sartori S, Boniver C, Toldo I, Salviati L. Electroclinical Features in Two Novel STRADA Patients and a Functional Yeast Assay for the Validation of Missense STRADA Mutations. Pediatr Neurol 2023; 148:152-156. [PMID: 37722301 DOI: 10.1016/j.pediatrneurol.2023.08.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 08/11/2023] [Accepted: 08/14/2023] [Indexed: 09/20/2023]
Abstract
Loss of function of the STRADA gene, an upstream mTOR inhibitor, causes a rare neurodevelopmental disorder characterized by polyhydramnios, megalencephaly, and symptomatic epilepsy (PMSE syndrome). Patients display a homogeneous phenotype including early-onset drug-resistant epilepsy, severe psychomotor delay, multisystemic comorbidities, and increased risk of premature death. The administration of sirolimus, an mTOR inhibitor, is helpful in controlling seizures in this syndrome. We report the electroclinical phenotype of two novel patients and the development of a yeast model to validate the pathogenicity of missense variants. Patient 1 harbored a missense STRADA variant and had a peculiar electroclinical phenotype with a relatively mild epilepsy course. Patient 2 harbored a truncating STRADA variant and showed a typical PMSE phenotype and a favorable response to early treatment with sirolimus. When we modeled the p.(Ser264Arg) STRADA change in its yeast homolog SPS1, it impaired SPS1 function. The results underlie the importance of a timely molecular diagnosis in these patients and show that yeast is a simple yet effective model to validate the pathogenicity of missense variants.
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Affiliation(s)
- Caterina Ancora
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | - Marco Marchi
- Clinical Genetics Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy; Clinical Genetics Lab, Città della Speranza Pediatric Research Institute, Padua, Italy
| | - Claudia Maria Bonardi
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | - Geppo Sartori
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | | | - Daniela Zuccarello
- Clinical Genetics Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | | | - Margherita Nosadini
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | - Stefano Sartori
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | - Clementina Boniver
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy
| | - Irene Toldo
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy.
| | - Leonardo Salviati
- Clinical Genetics Unit, Department of Women's and Children's Health, University of Padua, Padua, Italy; Clinical Genetics Lab, Città della Speranza Pediatric Research Institute, Padua, Italy
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Al Anazi AH, Ammar AS, Al-Hajj M, Cyrus C, Aljaafari D, Khoda I, Abdelfatah AK, Alsulaiman AA, Alanazi F, Alanazi R, Gandla D, Lad H, Barayan S, Keating BJ, Al-Ali AK. Whole-exome sequencing of a Saudi epilepsy cohort reveals association signals in known and potentially novel loci. Hum Genomics 2022; 16:71. [PMID: 36539902 PMCID: PMC9764464 DOI: 10.1186/s40246-022-00444-6] [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: 09/08/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Epilepsy, a serious chronic neurological condition effecting up to 100 million people globally, has clear genetic underpinnings including common and rare variants. In Saudi Arabia, the prevalence of epilepsy is high and caused mainly by perinatal and genetic factors. No whole-exome sequencing (WES) studies have been performed to date in Saudi Arabian epilepsy cohorts. This offers a unique opportunity for the discovery of rare genetic variants impacting this disease as there is a high rate of consanguinity among large tribal pedigrees. RESULTS We performed WES on 144 individuals diagnosed with epilepsy, to interrogate known epilepsy-related genes for known and functional novel variants. We also used an American College of Medical Genetics (ACMG) guideline-based variant prioritization approach in an attempt to discover putative causative variants. We identified 32 potentially causative pathogenic variants across 30 different genes in 44/144 (30%) of these Saudi epilepsy individuals. We also identified 232 variants of unknown significance (VUS) across 101 different genes in 133/144 (92%) subjects. Strong enrichment of variants of likely pathogenicity was observed in previously described epilepsy-associated loci, and a number of putative pathogenic variants in novel loci are also observed. CONCLUSION Several putative pathogenic variants in known epilepsy-related loci were identified for the first time in our population, in addition to several potential new loci which may be prioritized for further investigation.
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Affiliation(s)
- Abdulrahman H. Al Anazi
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Ahmed S. Ammar
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Mahmoud Al-Hajj
- grid.415296.d0000 0004 0607 1539Department of Neurosurgery, King Fahd Hospital, Alhafof, Saudi Arabia
| | - Cyril Cyrus
- grid.411975.f0000 0004 0607 035XDepartment of Clinical Biochemistry, College of Medicine, Imam Abdulrahman Bin Faisal University, P. O. Box 1982, 31441 Dammam, Saudi Arabia
| | - Danah Aljaafari
- grid.411975.f0000 0004 0607 035XDepartment of Neurology, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Iname Khoda
- grid.411975.f0000 0004 0607 035XDepartment of Neurology, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Ahmed K. Abdelfatah
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Abdullah A. Alsulaiman
- grid.411975.f0000 0004 0607 035XDepartment of Neurology, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Firas Alanazi
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Rawan Alanazi
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Divya Gandla
- grid.25879.310000 0004 1936 8972Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA USA
| | - Hetal Lad
- grid.25879.310000 0004 1936 8972Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA USA
| | - Samar Barayan
- grid.411975.f0000 0004 0607 035XDepartment of Neurosurgery, King Fahd Hospital of the University, Alkhobar, College of Medicine, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
| | - Brendan J. Keating
- grid.25879.310000 0004 1936 8972Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA USA
| | - Amein K. Al-Ali
- grid.411975.f0000 0004 0607 035XDepartment of Clinical Biochemistry, College of Medicine, Imam Abdulrahman Bin Faisal University, P. O. Box 1982, 31441 Dammam, Saudi Arabia
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Moloney PB, Cavalleri GL, Delanty N. Epilepsy in the mTORopathies: opportunities for precision medicine. Brain Commun 2021; 3:fcab222. [PMID: 34632383 PMCID: PMC8495134 DOI: 10.1093/braincomms/fcab222] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 08/23/2021] [Accepted: 08/30/2021] [Indexed: 01/16/2023] Open
Abstract
The mechanistic target of rapamycin signalling pathway serves as a ubiquitous regulator of cell metabolism, growth, proliferation and survival. The main cellular activity of the mechanistic target of rapamycin cascade funnels through mechanistic target of rapamycin complex 1, which is inhibited by rapamycin, a macrolide compound produced by the bacterium Streptomyces hygroscopicus. Pathogenic variants in genes encoding upstream regulators of mechanistic target of rapamycin complex 1 cause epilepsies and neurodevelopmental disorders. Tuberous sclerosis complex is a multisystem disorder caused by mutations in mechanistic target of rapamycin regulators TSC1 or TSC2, with prominent neurological manifestations including epilepsy, focal cortical dysplasia and neuropsychiatric disorders. Focal cortical dysplasia type II results from somatic brain mutations in mechanistic target of rapamycin pathway activators MTOR, AKT3, PIK3CA and RHEB and is a major cause of drug-resistant epilepsy. DEPDC5, NPRL2 and NPRL3 code for subunits of the GTPase-activating protein (GAP) activity towards Rags 1 complex (GATOR1), the principal amino acid-sensing regulator of mechanistic target of rapamycin complex 1. Germline pathogenic variants in GATOR1 genes cause non-lesional focal epilepsies and epilepsies associated with malformations of cortical development. Collectively, the mTORopathies are characterized by excessive mechanistic target of rapamycin pathway activation and drug-resistant epilepsy. In the first large-scale precision medicine trial in a genetically mediated epilepsy, everolimus (a synthetic analogue of rapamycin) was effective at reducing seizure frequency in people with tuberous sclerosis complex. Rapamycin reduced seizures in rodent models of DEPDC5-related epilepsy and focal cortical dysplasia type II. This review outlines a personalized medicine approach to the management of epilepsies in the mTORopathies. We advocate for early diagnostic sequencing of mechanistic target of rapamycin pathway genes in drug-resistant epilepsy, as identification of a pathogenic variant may point to an occult dysplasia in apparently non-lesional epilepsy or may uncover important prognostic information including, an increased risk of sudden unexpected death in epilepsy in the GATORopathies or favourable epilepsy surgery outcomes in focal cortical dysplasia type II due to somatic brain mutations. Lastly, we discuss the potential therapeutic application of mechanistic target of rapamycin inhibitors for drug-resistant seizures in GATOR1-related epilepsies and focal cortical dysplasia type II.
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Affiliation(s)
- Patrick B Moloney
- FutureNeuro, the Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, Dublin, D02 VN51, Ireland
| | - Gianpiero L Cavalleri
- FutureNeuro, the Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, Dublin, D02 VN51, Ireland
| | - Norman Delanty
- FutureNeuro, the Science Foundation Ireland Research Centre for Chronic and Rare Neurological Diseases, Royal College of Surgeons in Ireland, Dublin, D02 VN51, Ireland
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