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Mastrangelo M, Greco C, Tolve M, Bartolini E, Russo A, Nicita F, Pruna D, Galli J, Favaro J, Terrone G, De Felice C, Pisani F. Epilepsy phenotypes across the different age-ranges in IQSEC2-related encephalopathy: An Italian multicentre retrospective cohort study. Seizure 2024; 119:119-127. [PMID: 38851096 DOI: 10.1016/j.seizure.2024.06.002] [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: 04/23/2024] [Revised: 05/29/2024] [Accepted: 06/03/2024] [Indexed: 06/10/2024] Open
Abstract
BACKGROUND Epilepsy is a hallmark of IQSEC2-related encephalopathy within a phenotypic variability ranging between early onset epileptic and developmental encephalopathy and X-linked intellectual disability with epilepsy. PATIENTS AND METHODS Data including demographic aspects, gene variants, seizure semiology and timing, EEG features, neuroimaging and response to therapy were retrospectively collected in patients with IQSEC2-related epilepsy referring to 8 Italian tertiary centres. RESULTS The reported cohort included 11 patients (8 males and 3 females). Mean age at the onset of epilepsy was 3.90±2.80 years. No cases were reported in the first year of life. No specific epileptic syndromes were recognized. Predominant seizure-types in the age range 12-36 months included focal onset tonic seizures with impaired awareness, myoclonic seizures, and late onset spasms. Generalized motor seizures were predominant in patients between 3 and 6 years and between 12 and 18 years while focal motor seizures with impaired awareness were the most represented types between 6 and 12 years. No patients experienced status epilepticus. EEG patterns included a delayed maturation of EEG organization, irregular focal or diffuse slow activity, multifocal or diffuse epileptiform abnormalities. No structural epileptogenic lesions were detected at MRI. Valproate, lamotrigine, clobazam, topiramate and levetiracetam were the most used antiseizure medication. Complete seizure freedom was achieved only in 2 patients. CONCLUSIONS Onset of epilepsy after the first year of age, predominance of focal seizures with impaired awareness and generalized motor seizures, no pathognomonic underlying epileptic syndrome and infrequent occurrence of status epilepticus emerged as the main features of IQSEC2-related epilepsy phenotype.
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Affiliation(s)
- Mario Mastrangelo
- Woman/Child Health and Urological Sciences Department, Sapienza University of Rome, Rome, Italy; Unit of Child Neurology and Psychiatry, Department of Neuroscience/Mental Health-Azienda Ospedaliero Universitaria Policlinico Umberto, Rome, Italy.
| | - Carlo Greco
- Department of Human Neuroscience-Sapienza, University of Rome, Rome, Italy
| | - Manuela Tolve
- Unit of Clinical Pathology, Azienda Ospedalieo Universitaria Policilinico Umberto I, Rome, Italy
| | - Emanuele Bartolini
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Angelo Russo
- Istituto delle Scienze Neurologiche di Bologna, UOC Neuropsichiatria dell'età Pediatrica, IRCCS, Bologna, Italy
| | - Francesco Nicita
- Unit of Neuromuscolar and Neurodegenerative Disorders, IRCCS Bambino Gesù Children Hospital, Rome, Italy
| | - Dario Pruna
- Child Neurology and Epilepsy Unit Pediatric Department ARNAS Brotzu Cagliari, Italy
| | - Jessica Galli
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Jacopo Favaro
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children Health, University of Padua, Padua 35128, Italy
| | - Gaetano Terrone
- Child Neuropsychiatry Unit, Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy
| | - Claudio De Felice
- Pediatrics Unit, University Hospital Azienda Ospedaliera Universitaria Senese, Siena, Italy
| | - Francesco Pisani
- Unit of Child Neurology and Psychiatry, Department of Neuroscience/Mental Health-Azienda Ospedaliero Universitaria Policlinico Umberto, Rome, Italy; Department of Human Neuroscience-Sapienza, University of Rome, Rome, Italy
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Bai G, Li H, Qin P, Guo Y, Yang W, Lian Y, Ye F, Chen J, Wu M, Huang R, Li J, Lu Y, Zhang M. Ca2+-induced release of IQSEC2/BRAG1 autoinhibition under physiological and pathological conditions. J Cell Biol 2023; 222:e202307117. [PMID: 37787765 PMCID: PMC10548395 DOI: 10.1083/jcb.202307117] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/31/2023] [Accepted: 09/14/2023] [Indexed: 10/04/2023] Open
Abstract
IQSEC2 (aka BRAG1) is a guanine nucleotide exchange factor (GEF) highly enriched in synapses. As a top neurodevelopmental disorder risk gene, numerous mutations are identified in Iqsec2 in patients with intellectual disabilities accompanied by other developmental, neurological, and psychiatric symptoms, though with poorly understood underlying molecular mechanisms. The atomic structures of IQSECs, together with biochemical analysis, presented in this study reveal an autoinhibition and Ca2+-dependent allosteric activation mechanism for all IQSECs and rationalize how each identified Iqsec2 mutation can alter the structure and function of the enzyme. Transgenic mice modeling two pathogenic variants of Iqsec2 (R359C and Q801P), with one activating and the other inhibiting the GEF activity of the enzyme, recapitulate distinct clinical phenotypes in patients. Our study demonstrates that different mutations on one gene such as Iqsec2 can have distinct neurological phenotypes and accordingly will require different therapeutic strategies.
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Affiliation(s)
- Guanhua Bai
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Hao Li
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Pengwei Qin
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Yiqing Guo
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Wanfa Yang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Yinmiao Lian
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Fei Ye
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Jianxin Chen
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Meiling Wu
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Ruifeng Huang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Youming Lu
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Mingjie Zhang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen, China
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Liu X, Zhang S, Wan L, Zhang X, Wang H, Zhang H, Zhu G, Liang Y, Yan H, Zhang B, Yang G. IQSEC2-related encephalopathy in male children: Novel mutations and phenotypes. Front Mol Neurosci 2022; 15:984776. [PMID: 36267700 PMCID: PMC9577604 DOI: 10.3389/fnmol.2022.984776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/30/2022] [Indexed: 11/13/2022] Open
Abstract
The isoleucine–glutamine (IQ) motif and Sec7 domain-containing protein 2 (IQSEC2) gene, located at Xp11. 2, are associated with nervous system diseases, such as epilepsy, autism, and intellectual disabilities. Gender-related differences in the severity of phenotype severity have been described previously. Here, we report the details of seven male children with IQSEC2 mutations from different families. During this investigation, we explored the relationship between the genotype and phenotype of IQSEC2 mutations; to do so, we recruited seven children with pathogenic/likely pathogenic IQSEC2 mutations who were diagnosed with global developmental delay and/or epilepsy. Their clinical features were assessed, and Trio-based whole-exome sequencing (trio WES) was conducted in seven pedigrees. A variety of algorithms and computational tools were used to calculate the pathogenicity, protein stability, conservation, side chain properties, and protein-protein interactions of mutated proteins. The seven patients ranged in age from 18 months to 5 years. Among them, six children were found to have both developmental delay and epilepsy, and one child only exhibited developmental delay. Four novel mutations (c.316C > T, c.443_4 44dup, c.3235T > C, and c.1417G > T) were newly reported. Two patients did not have truncated aberrant proteins caused by missense mutations. Still, they did have severe phenotypes, such as early-onset epilepsy in infancy, because the mutations were located in domains like the pleckstrin homology and IQ calmodulin-binding motif domains. The bioinformatics analysis also proved that missense mutations may be located in the functional region, which affects protein stability and is harmful. In summary, severe phenotypes, such as early-onset epilepsy in infancy, occur in male patients with a missense mutation in specific domains (e.g., pleckstrin homology and IQ calmodulin-binding motif domains). Some female individuals with IQSEC2 mutations may be asymptomatic because of the skewed inactivation of the X chromosome.
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Affiliation(s)
- Xinting Liu
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- Medical School of Chinese PLA, Beijing, China
| | - Shan Zhang
- Medical School of Chinese PLA, Beijing, China
- Fuxing Road Clinic, Jingnan Medical District, Chinese PLA General Hospital, Beijing, China
| | - Lin Wan
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- Medical School of Chinese PLA, Beijing, China
| | - Xiaoli Zhang
- Department of Pediatrics, The Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | - Haiping Wang
- Department of Pediatric Neurology, Hangzhou Children's Hospital, Hangzhou, China
| | - Hongwei Zhang
- Department of Neurology, Jinan Children's Hospital, Jinan, China
| | - Gang Zhu
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- Medical School of Chinese PLA, Beijing, China
| | - Yan Liang
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- Medical School of Chinese PLA, Beijing, China
| | - Huimin Yan
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- Medical School of Chinese PLA, Beijing, China
| | - Bo Zhang
- Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
- Biostatistics and Research Design Center, Institutional Centers for Clinical and Translational Research, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
- Bo Zhang
| | - Guang Yang
- Department of Pediatrics, The First Medical Center, Chinese PLA General Hospital, Beijing, China
- Senior Department of Pediatrics, The Seventh Medical Center of PLA General Hospital, Beijing, China
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- *Correspondence: Guang Yang
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Wayhelova M, Vallova V, Broz P, Mikulasova A, Loubalova D, Filkova H, Smetana J, Drabova K, Gaillyova R, Kuglik P. Novel de novo pathogenic variant in the GNAI1 gene as a cause of severe disorders of intellectual development. J Hum Genet 2021; 67:209-214. [PMID: 34819662 DOI: 10.1038/s10038-021-00988-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 11/09/2022]
Abstract
Pathogenic sequence variant in the GNAI1 gene were recently introduced as a cause of novel syndrome with a manifestation of variable developmental delay and autistic features. In our study, we report a case of monozygotic twins with severe intellectual disability and motor delay and developmental dysphasia. Both probands and their parents were examined using multi-step molecular diagnostic algorithm including whole-exome sequencing (WES), resulting in the identification of a novel, de novo pathogenic sequence variant in the GNAI1 gene, NM_002069.6:c.815 A>G, p.(Asp272Gly) in probands. Using WES we also verified the microarray findings of a familial 8q24.23q24.3 duplication and heterozygous 5q13.2 deletion, not associated with clinical symptoms in probands. Our results confirmed the role of the GNAI1 gene in the pathogenesis of syndromic neurodevelopmental disorders. They support trio- or quatro-based WES as a suitable molecular diagnostics method for the simultaneous detection of clinically relevant sequence variants and CNVs in individuals with neurodevelopmental disorders and rare diseases.
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Affiliation(s)
- Marketa Wayhelova
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic. .,Laboratory of Cytogenomics, Centre of Molecular Biology and Genetics, Department of Internal Medicine, Haematology and Oncology, University Hospital Brno, Brno, Czech Republic. .,Department of Medical Genetics and Genomics, University Hospital Brno, Brno, Czech Republic.
| | - Vladimira Vallova
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.,Laboratory of Cytogenomics, Centre of Molecular Biology and Genetics, Department of Internal Medicine, Haematology and Oncology, University Hospital Brno, Brno, Czech Republic
| | - Petr Broz
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic.,Department of Biology and Medical Genetics, 2nd Faculty of Medicine, Charles University Prague and Faculty Hospital Motol, Prague, Czech Republic
| | - Aneta Mikulasova
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Dominika Loubalova
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Hana Filkova
- Laboratory of Cytogenomics, Centre of Molecular Biology and Genetics, Department of Internal Medicine, Haematology and Oncology, University Hospital Brno, Brno, Czech Republic
| | - Jan Smetana
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic
| | - Klara Drabova
- Department of Medical Genetics and Genomics, University Hospital Brno, Brno, Czech Republic
| | - Renata Gaillyova
- Department of Medical Genetics and Genomics, University Hospital Brno, Brno, Czech Republic
| | - Petr Kuglik
- Department of Experimental Biology, Faculty of Science, Masaryk University, Brno, Czech Republic. .,Laboratory of Cytogenomics, Centre of Molecular Biology and Genetics, Department of Internal Medicine, Haematology and Oncology, University Hospital Brno, Brno, Czech Republic.
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Brand BA, Blesson AE, Smith-Hicks CL. The Impact of X-Chromosome Inactivation on Phenotypic Expression of X-Linked Neurodevelopmental Disorders. Brain Sci 2021; 11:brainsci11070904. [PMID: 34356138 PMCID: PMC8305405 DOI: 10.3390/brainsci11070904] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 06/16/2021] [Accepted: 06/20/2021] [Indexed: 12/20/2022] Open
Abstract
Nearly 20% of genes located on the X chromosome are associated with neurodevelopmental disorders (NDD) due to their expression and role in brain functioning. Given their location, several of these genes are either subject to or can escape X-chromosome inactivation (XCI). The degree to which genes are subject to XCI can influence the NDD phenotype between males and females. We provide a general review of X-linked NDD genes in the context of XCI and detailed discussion of the sex-based differences related to MECP2 and FMR1, two common X-linked causes of NDD that are subject to XCI. Understanding the effects of XCI on phenotypic expression of NDD genes may guide the development of stratification biomarkers in X-linked disorders.
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Affiliation(s)
- Boudewien A Brand
- Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, MD 21205, USA; (B.A.B.); (A.E.B.)
| | - Alyssa E Blesson
- Center for Autism and Related Disorders, Kennedy Krieger Institute, Baltimore, MD 21205, USA; (B.A.B.); (A.E.B.)
| | - Constance L. Smith-Hicks
- Department of Neurology and Developmental Medicine, Kennedy Krieger Institute, Baltimore, MD 21205, USA
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
- Correspondence:
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IQSEC2 mutation associated with epilepsy, intellectual disability, and autism results in hyperexcitability of patient-derived neurons and deficient synaptic transmission. Mol Psychiatry 2021; 26:7498-7508. [PMID: 34535765 PMCID: PMC8873005 DOI: 10.1038/s41380-021-01281-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 07/09/2021] [Accepted: 08/24/2021] [Indexed: 12/03/2022]
Abstract
Mutations in the IQSEC2 gene are associated with drug-resistant, multifocal infantile and childhood epilepsy; autism; and severe intellectual disability (ID). We used induced pluripotent stem cell (iPSC) technology to obtain hippocampal neurons to investigate the neuropathology of IQSEC2-mediated disease. The neurons were characterized at three-time points during differentiation to assess developmental progression. We showed that immature IQSEC2 mutant dentate gyrus (DG) granule neurons were extremely hyperexcitable, exhibiting increased sodium and potassium currents compared to those of CRISPR-Cas9-corrected isogenic controls, and displayed dysregulation of genes involved in differentiation and development. Immature IQSEC2 mutant cultured neurons exhibited a marked reduction in the number of inhibitory neurons, which contributed further to hyperexcitability. As the mutant neurons aged, they became hypoexcitable, exhibiting reduced sodium and potassium currents and a reduction in the rate of synaptic and network activity, and showed dysregulation of genes involved in synaptic transmission and neuronal differentiation. Mature IQSEC2 mutant neurons were less viable than wild-type mature neurons and had reduced expression of surface AMPA receptors. Our studies provide mechanistic insights into severe infantile epilepsy and neurodevelopmental delay associated with this mutation and present a human model for studying IQSEC2 mutations in vitro.
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