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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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Zhang X, Han Y, Yang L, Xu N, Zhu L, Qiu S, Li Y, Xu L, Yu X. Clinical phenotype and genetic characteristics of SZT2 related diseases: A case report and literature review. Seizure 2024; 114:111-120. [PMID: 38134649 DOI: 10.1016/j.seizure.2023.12.008] [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: 05/30/2023] [Revised: 12/11/2023] [Accepted: 12/13/2023] [Indexed: 12/24/2023] Open
Abstract
PURPOSE Seizure threshold 2 protein homolog gene (SZT2, MIM: 615463) related diseases are extremely rare autosomal recessive disorders with a wide spectrum of clinical phenotypes ranging from mild intellectual impairment to severe developmental epileptic encephalopathy (DEE). Most SZT2 related diseases are accompanied by craniofacial malformation and corpus callosum malformation. This study attempts to analyze and summarize the clinical phenotype and genetic characteristics of SZT2 related diseases, providing a basis for early diagnosis, treatment, and prognosis. METHOD We analyzed the clinical characteristics of a Chinese child with pathogenic variants of SZT2. We also performed whole-exome sequencing (WES) on the patient. In addition, we conducted a literature review of previously reported patients with pathogenic mutations in the SZT2 gene. RESULT The proband was a boy aged 1 year and 9 months with severe global developmental delay, transient drug-controlled focal epilepsy, cluster epilepsy, autism spectrum disorder, craniofacial deformity, hypotonia, focal EEG discharge, corpus callosum malformation, and persistent cavum septum pellucidum. WES revealed that the patient carried the SZT2 gene c.7584dupA and c.6302A>C complex heterozygous variants; the former being Likely Pathogenic (LP) and the latter Uncertain Significance (VUS) according to ACMG classification guidelines. According to our literature review, 43 cases of SZT2 related diseases have been reported so far; these include 15 cases with homozygous variations and 28 cases with complex heterozygous variations. A total of 57 types of variation were found, including 47 genetic variants, 2 de novo variants, and 8 unknown genetic modes. In addition, 2 high-frequency variants were found (c.5949_5951delTGT and c.6553C>T). The main clinical manifestations of the 40 patients were global developmental delay (GDD) of varying degrees (38/40, 95.00 %), seizures (36/40, 90.00 %), cranial deformity (27/40, 67.50 %), facial deformity (22/40, 55.00 %), hypotonia (22/40, 55.00 %), abnormal interseizure EEG discharge (26/40, 65.00 %), slow background activity (20/40, 50.00 %), corpus callosum deformity (18/40, 45.00 %). There was also one case of sudden unexpected death in epilepsy (SUDEP) and 3 cases of death from infection. In addition, three fetuses with the same variant had hydrocephalus and encephalocele. CONCLUSION The compound heterozygous mutation of c.7584dupA and c.6302A>C in the SZT2 gene is the genetic etiology of this patient, expanding the mutation spectrum of SZT2 related diseases. Early genetic testing is the best choice for clear diagnosis, treatment, and prognosis.
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Affiliation(s)
- Xin Zhang
- Postgrad Training Base Jinzhou Med Univ, Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China; Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Yuzeng Han
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Li Yang
- Postgrad Training Base Jinzhou Med Univ, Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China; Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China.
| | - Na Xu
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Liping Zhu
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Shiyan Qiu
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Yufen Li
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Liyun Xu
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
| | - Xixi Yu
- Department of Pediatrics, Linyi People's Hospital, Linyi, Shandong 276003, PR China
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de Pedro Baena S, Sariego Jamardo A, Castro P, López González FJ, Sánchez Carpintero R, Cerisola A, Troncoso M, Witting S, Barrios A, Fons C, López Pisón J, Ortigoza‐Escobar JD. Exploring the Spectrum of RHOBTB2 Variants Associated with Developmental Encephalopathy 64: A Case Series and Literature Review. Mov Disord Clin Pract 2023; 10:1671-1679. [PMID: 37982109 PMCID: PMC10654829 DOI: 10.1002/mdc3.13880] [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: 09/13/2022] [Revised: 08/20/2023] [Accepted: 08/24/2023] [Indexed: 11/21/2023] Open
Abstract
Background Rho-related BTB domain-containing protein 2 (RHOBTB2) is a protein that interacts with cullin-3, a crucial E3 ubiquitin ligase for mitotic cell division. RHOBTB2 has been linked to early infantile epileptic encephalopathy, autosomal dominant type 64 (OMIM618004), in 34 reported patients. Methods We present a case series of seven patients with RHOBTB2-related disorders (RHOBTB2-RD), including a description of a novel heterozygous variant. We also reviewed previously published cases of RHOBTB2-RD. Results The seven patients had ages ranging from 2 years and 8 months to 26 years, and all had experienced seizures before the age of one (onset, 4-12 months, median, 4 months), including various types of seizures. All patients in this cohort also had a movement disorder (onset, 0.3-14 years, median, 1.5 years). Six of seven had a baseline movement disorder, and one of seven only had paroxysmal dystonia. Stereotypies were noted in four of six, choreodystonia in three of six, and ataxia in one case with multiple movement phenotypes at baseline. Paroxysmal movement disorders were observed in six of seven patients for whom carbamazepine or oxcarbazepine treatment was effective in controlling acute or paroxysmal movement disorders. Four patients had acute encephalopathic episodes at ages 4 (one patient) and 6 (three patients), which improved following treatment with methylprednisolone. Magnetic resonance imaging scans revealed transient fluid-attenuated inversion recovery abnormalities during these episodes, as well as myelination delay, thin corpus callosum, and brain atrophy. One patient had a novel RHOBTB2 variant (c.359G>A/p.Gly120Glu). Conclusion RHOBTB2-RD is characterized by developmental delay or intellectual disability, early-onset seizures, baseline movement disorders, acute or paroxysmal motor phenomena, acquired microcephaly, and episodes of acute encephalopathy. Early onsets of focal dystonia, acute encephalopathic episodes, episodes of tongue protrusion, or peripheral vasomotor disturbances are important diagnostic clues. Treatment with carbamazepine or oxcarbazepine was found to be effective in controlling acute or paroxysmal movement disorders. Our study highlights the clinical features and treatment response of RHOBTB2-RD.
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Affiliation(s)
| | - Andrea Sariego Jamardo
- Pediatric Neurology DepartmentHospital Universitario Marqués de ValdecillaSantanderSpain
| | - Pedro Castro
- Department of Pediatric NeurologyHospital Gregorio MarañónMadridSpain
| | | | | | - Alfredo Cerisola
- Pediatric Neurology DepartmentInstitut de Recerca, Hospital Sant Joan de Déu BarcelonaBarcelonaSpain
| | - Mónica Troncoso
- Centro de Referencia Nacional en Defectos Congénitos y Enfermedades Raras (CRENADECER) del Banco de Previsión Social (BPS), Uruguay; Cátedra de Neuropediatría, Facultad de MedicinaUniversidad de la RepúblicaMontevideoUruguay
| | - Scarlet Witting
- Centro de Referencia Nacional en Defectos Congénitos y Enfermedades Raras (CRENADECER) del Banco de Previsión Social (BPS), Uruguay; Cátedra de Neuropediatría, Facultad de MedicinaUniversidad de la RepúblicaMontevideoUruguay
| | - Andrés Barrios
- Centro de Referencia Nacional en Defectos Congénitos y Enfermedades Raras (CRENADECER) del Banco de Previsión Social (BPS), Uruguay; Cátedra de Neuropediatría, Facultad de MedicinaUniversidad de la RepúblicaMontevideoUruguay
| | - Carmen Fons
- Pediatric Neurology DepartmentInstitut de Recerca, Hospital Sant Joan de Déu BarcelonaBarcelonaSpain
| | - Javier López Pisón
- Child Neurology ServiceHospital San Borja Arriarán, Universidad de ChileSantiagoChile
| | - Juan Darío Ortigoza‐Escobar
- Pediatric Neurology DepartmentHospital Infantil Universitario Miguel ServetZaragozaSpain
- Movement Disorders Unit, Pediatric Neurology DepartmentInstitut de Recerca, Hospital Sant Joan de Déu BarcelonaBarcelonaSpain
- U‐703 Centre for Biomedical Research on Rare Diseases (CIBER‐ER)Instituto de Salud Carlos IIIBarcelonaSpain
- European Reference Network for Rare Neurological Diseases (ERN‐RND)BarcelonaSpain
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4
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Muthaffar OY, Jan MMS, Alyazidi AS, Alotibi TK, Alsulami EA. Insight into Genetic Mutations of SZT2: Is It a Syndrome? Biomedicines 2023; 11:2402. [PMID: 37760843 PMCID: PMC10525120 DOI: 10.3390/biomedicines11092402] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 08/21/2023] [Accepted: 08/23/2023] [Indexed: 09/29/2023] Open
Abstract
BACKGROUND The seizure threshold 2 (SZT2) gene encodes a protein of unknown function, which is widely expressed, confers a low seizure threshold, and enhances epileptogenesis. It also comprises the KICSTOR protein complex, which inhibits the mTORC1 pathway. A pathogenic variant in the SZT2 gene could result in hyperactive mTORC1 signaling, which can lead to several neurological disorders. AIM OF THE STUDY To review every reported case and present two novel cases to expand the current knowledge and understanding of the mutation. METHODS Whole exome sequencing (WES) was used to identify the novel cases and present their clinical and radiological findings. A detailed revision of the literature was conducted to illustrate and compare findings. The clinical, genetical, neuroimaging, and electrophysiological data were extracted. RESULTS The study included 16 female patients and 13 male patients in addition to the 2 novel male cases. Eighteen patients had heterozygous mutations; others were homozygous. The majority presented with facial dysmorphism (n = 22). Seizures were noted as the predominant hallmark (n = 26). Developmental delay and hypotonia were reported in 27 and 15 patients, respectively. The majority of patients had multifocal epileptiform discharges on the electroencephalogram (EEG) and short and thick corpus callosum on the magnetic resonance imaging (MRI). CONCLUSION Several promising features are becoming strongly linked to patients with SZT2 mutations. High variability among the cases was observed. Developmental delay and facial dysmorphism can be investigated as potential hallmarks; aiding clinicians in diagnosing the condition and optimizing management plans.
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Affiliation(s)
- Osama Y. Muthaffar
- Department of Pediatrics, Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia; (O.Y.M.); (M.M.S.J.)
| | - Mohammed M. S. Jan
- Department of Pediatrics, Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia; (O.Y.M.); (M.M.S.J.)
| | - Anas S. Alyazidi
- Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia; (T.K.A.); (E.A.A.)
| | - Taif K. Alotibi
- Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia; (T.K.A.); (E.A.A.)
| | - Eman A. Alsulami
- Faculty of Medicine, King Abdulaziz University, Jeddah 21589, Saudi Arabia; (T.K.A.); (E.A.A.)
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5
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Figlia G, Müller S, Hagenston AM, Kleber S, Roiuk M, Quast JP, Ten Bosch N, Carvajal Ibañez D, Mauceri D, Martin-Villalba A, Teleman AA. Brain-enriched RagB isoforms regulate the dynamics of mTORC1 activity through GATOR1 inhibition. Nat Cell Biol 2022; 24:1407-1421. [PMID: 36097071 PMCID: PMC9481464 DOI: 10.1038/s41556-022-00977-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 07/13/2022] [Indexed: 12/26/2022]
Abstract
Mechanistic target of rapamycin complex 1 (mTORC1) senses nutrient availability to appropriately regulate cellular anabolism and catabolism. During nutrient restriction, different organs in an animal do not respond equally, with vital organs being relatively spared. This raises the possibility that mTORC1 is differentially regulated in different cell types, yet little is known about this mechanistically. The Rag GTPases, RagA or RagB bound to RagC or RagD, tether mTORC1 in a nutrient-dependent manner to lysosomes where mTORC1 becomes activated. Although the RagA and B paralogues were assumed to be functionally equivalent, we find here that the RagB isoforms, which are highly expressed in neurons, impart mTORC1 with resistance to nutrient starvation by inhibiting the RagA/B GTPase-activating protein GATOR1. We further show that high expression of RagB isoforms is observed in some tumours, revealing an alternative strategy by which cancer cells can retain elevated mTORC1 upon low nutrient availability.
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Affiliation(s)
- Gianluca Figlia
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Heidelberg University, Heidelberg, Germany
| | - Sandra Müller
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Heidelberg University, Heidelberg, Germany
| | - Anna M Hagenston
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, INF 366, Heidelberg, Germany
| | - Susanne Kleber
- Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Mykola Roiuk
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Heidelberg University, Heidelberg, Germany
| | - Jan-Philipp Quast
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany.,Heidelberg University, Heidelberg, Germany
| | - Nora Ten Bosch
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Damian Carvajal Ibañez
- Heidelberg University, Heidelberg, Germany.,Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Daniela Mauceri
- Department of Neurobiology, Interdisciplinary Center for Neurosciences (IZN), Heidelberg University, INF 366, Heidelberg, Germany
| | - Ana Martin-Villalba
- Molecular Neurobiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Aurelio A Teleman
- Signal Transduction in Cancer and Metabolism, German Cancer Research Center (DKFZ), Heidelberg, Germany. .,Heidelberg University, Heidelberg, Germany.
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6
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Yang S, Yang LM, Liao HM, Fang HJ, Ning ZS, Liao CS, Wu LW. Genetic analysis of developmental and epileptic encephalopathy caused by novel biallelic SZT2 gene mutations in three Chinese Han infants: a case series and literature review. Neurol Sci 2022; 43:5039-5048. [DOI: 10.1007/s10072-022-06038-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 03/21/2022] [Indexed: 11/28/2022]
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7
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Calhoun JD, Aziz MC, Happ HC, Gunti J, Gleason C, Mohamed N, Zeng K, Hiller M, Bryant E, Mithal DS, Bellinski I, Kinsley L, Grimmel M, Schwaibold EMC, Smith-Hicks C, Chassevent A, Scala M, Accogli A, Torella A, Striano P, Capra V, Bird LM, Ben-Sahra I, Ekhilevich N, Hershkovitz T, Weiss K, Millichap J, Gerard EE, Carvill GL. mTORC1 functional assay reveals SZT2 loss-of-function variants and a founder in-frame deletion. Brain 2022; 145:1939-1948. [PMID: 35773235 PMCID: PMC9630660 DOI: 10.1093/brain/awab451] [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: 04/08/2021] [Revised: 10/27/2021] [Accepted: 11/19/2021] [Indexed: 11/14/2022] Open
Abstract
Biallelic pathogenic variants in SZT2 result in a neurodevelopmental disorder with shared features, including early-onset epilepsy, developmental delay, macrocephaly, and corpus callosum abnormalities. SZT2 is as a critical scaffolding protein in the amino acid sensing arm of the mTORC1 signalling pathway. Due to its large size (3432 amino acids), lack of crystal structure, and absence of functional domains, it is difficult to determine the pathogenicity of SZT2 missense and in-frame deletions, but these variants are increasingly detected and reported by clinical genetic testing in individuals with epilepsy. To exemplify this latter point, here we describe a cohort of 12 individuals with biallelic SZT2 variants and phenotypic overlap with SZT2-related neurodevelopmental disorders. However, the majority of individuals carried one or more SZT2 variants of uncertain significance (VUS), highlighting the need for functional characterization to determine, which, if any, of these VUS were pathogenic. Thus, we developed a novel individualized platform to identify SZT2 loss-of-function variants in the context of mTORC1 signalling and reclassify VUS. Using this platform, we identified a recurrent in-frame deletion (SZT2 p.Val1984del) which was determined to be a loss-of-function variant and therefore likely pathogenic. Haplotype analysis revealed that this single in-frame deletion is a founder variant in those of Ashkenazi Jewish ancestry. Moreover, this approach allowed us to tentatively reclassify all of the VUS in our cohort of 12 individuals, identifying five individuals with biallelic pathogenic or likely pathogenic variants. Clinical features of these five individuals consisted of early-onset seizures (median 24 months), focal seizures, developmental delay and macrocephaly similar to previous reports. However, we also show a widening of the phenotypic spectrum, as none of the five individuals had corpus callosum abnormalities, in contrast to previous reports. Overall, we present a rapid assay to resolve VUS in SZT2, identify a founder variant in individuals of Ashkenazi Jewish ancestry, and demonstrate that corpus callosum abnormalities is not a hallmark feature of this condition. Our approach is widely applicable to other mTORopathies including the most common causes of the focal genetic epilepsies, DEPDC5, TSC1/2, MTOR and NPRL2/3.
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Affiliation(s)
- Jeffrey D Calhoun
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Miriam C Aziz
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Hannah C Happ
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Jonathan Gunti
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Colleen Gleason
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Najma Mohamed
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Kristy Zeng
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Meredith Hiller
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Emily Bryant
- Ann and Robert H. Lurie Children's Hospital of Chicago Epilepsy Center and Division of Neurology, Chicago, IL 60610, USA
| | - Divakar S Mithal
- Ann and Robert H. Lurie Children's Hospital of Chicago Epilepsy Center and Division of Neurology, Chicago, IL 60610, USA
| | - Irena Bellinski
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Lisa Kinsley
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Mona Grimmel
- Ann & Robert H. Lurie Children's Hospital of Chicago, Department of Pediatrics, Epilepsy Center and Division of Neurology, Chicago, IL 60610, USA
| | - Eva M C Schwaibold
- Institute of Human Genetics, Heidelberg University, Heidelberg 69120, Germany
| | - Constance Smith-Hicks
- Department of Neurogenetics, Kennedy Krieger Institute, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Anna Chassevent
- Department of Neurogenetics, Kennedy Krieger Institute, Baltimore, MD 21205, USA
| | - Marcello Scala
- Giannina Gaslini Children's Hospital, Genova, GE 16147, Italy.,Medical Genetic Unit, IRCCS Istituto G.Gaslini, 16147 Genoa, Italy
| | - Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre (MUHC), Montreal, QC, H4A 3J1, Canada.,Department of Human Genetics, McGill University, Montreal, QC, Canada
| | - Annalaura Torella
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre (MUHC), Montreal, QC, H4A 3J1, Canada
| | - Pasquale Striano
- Giannina Gaslini Children's Hospital, Genova, GE 16147, Italy.,Medical Genetic Unit, IRCCS Istituto G.Gaslini, 16147 Genoa, Italy
| | - Valeria Capra
- Giannina Gaslini Children's Hospital, Genova, GE 16147, Italy.,Medical Genetic Unit, IRCCS Istituto G.Gaslini, 16147 Genoa, Italy
| | - Lynne M Bird
- Department of Human Genetics, McGill University, Montreal, QC, Canada
| | - Issam Ben-Sahra
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, NA 80078, Italy
| | - Nina Ekhilevich
- San Diego Department of Pediatrics and Rady Children's Hospital Division of Dysmorphology/Genetics, University of California, San Diego, CA 92161, USA
| | - Tova Hershkovitz
- San Diego Department of Pediatrics and Rady Children's Hospital Division of Dysmorphology/Genetics, University of California, San Diego, CA 92161, USA.,Department of Biochemistry and Molecular Genetics, Northwestern Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Karin Weiss
- San Diego Department of Pediatrics and Rady Children's Hospital Division of Dysmorphology/Genetics, University of California, San Diego, CA 92161, USA.,Department of Biochemistry and Molecular Genetics, Northwestern Feinberg School of Medicine, Chicago, IL 60610, USA
| | - John Millichap
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA.,Ann and Robert H. Lurie Children's Hospital of Chicago Epilepsy Center and Division of Neurology, Chicago, IL 60610, USA
| | - Elizabeth E Gerard
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA
| | - Gemma L Carvill
- Ken and Ruth Davee Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60610, USA.,Genetics Institute, Rambam Medical Center, Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.,Ruth and Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 3200003, Israel
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8
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Cherian A, Divya KP, Pavuluri H, Thomas B. The Dysfunctional Gangway: SZT2-associated Epilepsy with Thick Corpus Callosum. J Pediatr Neurosci 2021; 16:289-292. [PMID: 36531768 PMCID: PMC9757505 DOI: 10.4103/jpn.jpn_128_20] [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: 05/22/2020] [Accepted: 07/04/2020] [Indexed: 06/17/2023] Open
Abstract
Mutations in seizure threshold 2 (SZT2) gene on chromosome 1p34.2 are an of late identified cause of epilepsy and epileptic encephalopathy. We report a 3-year-old girl who presented with developmental delay, dysmorphic facies, refractory seizures, and subsequent developmental regression. Despite significant multifocal epileptiform abnormalities on her electroencephalogram, she had a paucity of generalized discharges indicating a functional deficiency of corpus callosum inspite of its increased thickness seen on magnetic resonance imaging. Her clinical exome sequencing revealed a homozygous single base pair duplication in the SZT2 gene that resulted in a frameshift mutation and premature truncation of the protein. Our case emphasizes the role of SZT2 gene in the diagnostic algorithm of early childhood refractory epilepsy especially in the context of a thick yet dysfunctional corpus callosum.
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Affiliation(s)
- Ajith Cherian
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, Kerala, India
| | - Kalikavil Puthanveedu Divya
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, Kerala, India
| | - Harini Pavuluri
- Department of Neurology, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, Kerala, India
| | - Bejoy Thomas
- Department of Imaging Sciences and Interventional Radiology, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Trivandrum, Kerala, India
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9
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Laighneach A, Desbonnet L, Kelly JP, Donohoe G, Morris DW. Meta-Analysis of Brain Gene Expression Data from Mouse Model Studies of Maternal Immune Activation Using Poly(I:C). Genes (Basel) 2021; 12:genes12091363. [PMID: 34573345 PMCID: PMC8471627 DOI: 10.3390/genes12091363] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Revised: 08/20/2021] [Accepted: 08/30/2021] [Indexed: 02/07/2023] Open
Abstract
Maternal immune activation (MIA) is a known risk factor for schizophrenia (SCZ) and autism spectrum disorder (ASD) and is often modelled in animal studies in order to study the effect of prenatal infection on brain function including behaviour and gene expression. Although the effect of MIA on gene expression are highly heterogeneous, combining data from multiple gene expression studies in a robust method may shed light on the true underlying biological effects caused by MIA and this could inform studies of SCZ and ASD. This study combined four RNA-seq and microarray datasets in an overlap analysis and ranked meta-analysis in order to investigate genes, pathways and cell types dysregulated in the MIA mouse models. Genes linked to SCZ and ASD and crucial in neurodevelopmental processes including neural tube folding, regulation of cellular stress and neuronal/glial cell differentiation were among the most consistently dysregulated in these ranked analyses. Gene ontologies including K+ ion channel function, neuron and glial cell differentiation, synaptic structure, axonal outgrowth, cilia function and lipid metabolism were also strongly implicated. Single-cell analysis identified excitatory and inhibitory cell types in the cortex, hippocampus and striatum that may be affected by MIA and are also enriched for genes associated with SCZ, ASD and cognitive phenotypes. This points to the cellular location of molecular mechanisms that may be consistent between the MIA model and neurodevelopmental disease, improving our understanding of its utility to study prenatal infection as an environmental stressor.
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Affiliation(s)
- Aodán Laighneach
- Centre for Neuroimaging, Cognition and Genomics, Discipline of Biochemistry and School of Psychology, National University of Ireland Galway, H91 TK33 Galway, Ireland; (A.L.); (G.D.)
| | - Lieve Desbonnet
- Discipline of Pharmacology and Therapeutics, National University of Ireland Galway, H91 TK33 Galway, Ireland; (L.D.); (J.P.K.)
| | - John P. Kelly
- Discipline of Pharmacology and Therapeutics, National University of Ireland Galway, H91 TK33 Galway, Ireland; (L.D.); (J.P.K.)
| | - Gary Donohoe
- Centre for Neuroimaging, Cognition and Genomics, Discipline of Biochemistry and School of Psychology, National University of Ireland Galway, H91 TK33 Galway, Ireland; (A.L.); (G.D.)
| | - Derek W. Morris
- Centre for Neuroimaging, Cognition and Genomics, Discipline of Biochemistry and School of Psychology, National University of Ireland Galway, H91 TK33 Galway, Ireland; (A.L.); (G.D.)
- Correspondence:
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10
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New avenues in molecular genetics for the diagnosis and application of therapeutics to the epilepsies. Epilepsy Behav 2021; 121:106428. [PMID: 31400936 DOI: 10.1016/j.yebeh.2019.07.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 06/14/2019] [Accepted: 07/06/2019] [Indexed: 11/22/2022]
Abstract
Genetic epidemiology studies have shown that most epilepsies involve some genetic cause. In addition, twin studies have helped strengthen the hypothesis that in most patients with epilepsy, a complex inheritance is involved. More recently, with the development of high-density single-nucleotide polymorphism (SNP) microarrays and next-generation sequencing (NGS) technologies, the discovery of genes related to the epilepsies has accelerated tremendously. Especially, the use of whole exome sequencing (WES) has had a considerable impact on the identification of rare genetic variants with large effect sizes, including inherited or de novo mutations in severe forms of childhood epilepsies. The identification of pathogenic variants in patients with these childhood epilepsies provides many benefits for patients and families, such as the confirmation of the genetic nature of the diseases. This process will allow for better genetic counseling, more accurate therapy decisions, and a significant positive emotional impact. However, to study the genetic component of the more common forms of epilepsy, the use of high-density SNP arrays in genome-wide association studies (GWAS) seems to be the strategy of choice. As such, researchers can identify loci containing genetic variants associated with the common forms of epilepsy. The knowledge generated over the past two decades about the effects of the mutations that cause the monogenic epilepsy is tremendous; however, the scientific community is just starting to apply this information in order to generate better target treatments.
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11
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ORN: Inferring patient-specific dysregulation status of pathway modules in cancer with OR-gate Network. PLoS Comput Biol 2021; 17:e1008792. [PMID: 33819263 PMCID: PMC8049496 DOI: 10.1371/journal.pcbi.1008792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 04/15/2021] [Accepted: 02/15/2021] [Indexed: 01/26/2023] Open
Abstract
Pathway level understanding of cancer plays a key role in precision oncology. However, the current amount of high-throughput data cannot support the elucidation of full pathway topology. In this study, instead of directly learning the pathway network, we adapted the probabilistic OR gate to model the modular structure of pathways and regulon. The resulting model, OR-gate Network (ORN), can simultaneously infer pathway modules of somatic alterations, patient-specific pathway dysregulation status, and downstream regulon. In a trained ORN, the differentially expressed genes (DEGs) in each tumour can be explained by somatic mutations perturbing a pathway module. Furthermore, the ORN handles one of the most important properties of pathway perturbation in tumours, the mutual exclusivity. We have applied the ORN to lower-grade glioma (LGG) samples and liver hepatocellular carcinoma (LIHC) samples in TCGA and breast cancer samples from METABRIC. Both datasets have shown abnormal pathway activities related to immune response and cell cycles. In LGG samples, ORN identified pathway modules closely related to glioma development and revealed two pathways closely related to patient survival. We had similar results with LIHC samples. Additional results from the METABRIC datasets showed that ORN could characterize critical mechanisms of cancer and connect them to less studied somatic mutations (e.g., BAP1, MIR604, MICAL3, and telomere activities), which may generate novel hypothesis for targeted therapy. Cellular functions are carried out by a set of gene products. Mutation of a single gene is often sufficient to disrupt certain biological functions and promote tumorigenesis. Therefore, genes participating in the same function are less likely to mutate in the same sample. Such phenomenon is called “mutual exclusivity”. In this study, our algorithm (ORN) has utilized this property to identify gene-level mutations that affect similar biological functions. It also considers mutations’ impact on mRNA expression. Functional modules identified by ORN tends to be mutually exclusive while causing similar differential expression profiles. When we applied ORN to lower-grade glioma and liver cancer datasets, we have identified gene modules significantly related to patient survival. Furthermore, across different types of cancer, ORN has connected well-known cancer driver mutations with genes whose functions remain unclear. These connections, once validated, can generate novel hypothesis for biologist to further investigate cancer mechanism and develop targeted therapy.
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12
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El Halabi T, Dirani M, Hotait M, Nasreddine W, Beydoun A. A novel possible familial cause of epilepsy of infancy with migrating focal seizures related to SZT2 gene variant. Epilepsia Open 2021; 6:73-78. [PMID: 33681650 PMCID: PMC7918305 DOI: 10.1002/epi4.12451] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 11/10/2020] [Accepted: 11/22/2020] [Indexed: 12/31/2022] Open
Abstract
Seizure threshold-2 (SZT2) gene variants have been associated with a decrease in seizure threshold resulting in variable phenotypic expressions ranging from mild-moderate intellectual disabilities without seizures, to an early-onset epileptic encephalopathy with severe cognitive impairment. In addition, hypotonia and distinctive facial dysmorphism, including a high forehead and to a lesser extent ptosis and down-slanting palpebral fissures, were present in the majority. We herein report a novel SZT2 variant in one of two siblings both diagnosed with epilepsy of infancy with migrating focal seizures (EIMFS). This report is the fourth to document a possible familial case in EIMFS, a condition that was not previously associated with SZT2 variant. This report expands the phenotypic expression of SZT2, corroborates the importance of genetic counseling in some cases of EIMFS, and highlights the efficacy of potassium bromide in controlling the seizures associated with this condition.
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Affiliation(s)
- Tarek El Halabi
- Neurology DepartmentAmerican University of Beirut Medical CenterBeirutLebanon
| | - Maya Dirani
- Neurology DepartmentAmerican University of Beirut Medical CenterBeirutLebanon
| | - Mostafa Hotait
- Neurology DepartmentAmerican University of Beirut Medical CenterBeirutLebanon
| | - Wassim Nasreddine
- Neurology DepartmentAmerican University of Beirut Medical CenterBeirutLebanon
| | - Ahmad Beydoun
- Neurology DepartmentAmerican University of Beirut Medical CenterBeirutLebanon
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13
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Trivisano M, Rivera M, Terracciano A, Ciolfi A, Napolitano A, Pepi C, Calabrese C, Digilio MC, Tartaglia M, Curatolo P, Vigevano F, Specchio N. Developmental and epileptic encephalopathy due to SZT2 genomic variants: Emerging features of a syndromic condition. Epilepsy Behav 2020; 108:107097. [PMID: 32402703 DOI: 10.1016/j.yebeh.2020.107097] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/04/2020] [Accepted: 04/04/2020] [Indexed: 10/24/2022]
Abstract
Seizure threshold 2 (SZT2) gene mutations have been associated with developmental and epileptic encephalopathies (DEEs). Following a literature review, we collected 22 patients and identified the main clinical features related to SZT2 variants that are epilepsy with onset within the first years of life, intellectual disability (ID), macrocephaly with dysmorphic facial features, corpus callosum (CC) shape abnormalities, and cortical migration disorders. Moreover, we identified the c.7825T>G homozygous missense variant in SZT2 in two female siblings presenting with focal seizures, mild-moderate ID, behavioral disturbances, and facial dysmorphisms. Interictal Electroencephalogram (EEG) and ictal EEG were both informative and revealed, respectively, temporal bilateral asynchronous slow and epileptiform abnormalities and a focal onset in both of them. Neuroimaging study revealed a thick and abnormally shaped CC. Seizure threshold 2 has been identified as a component of the KICSTOR complex, a newly recognized protein complex involved in the mammalian target of rapamycin (mTOR) pathway. mTOR signaling dysregulation represents common pathogenetic mechanisms that can explain the presence of both epileptogenesis and ID. Even if few cases had been reported, a new clinical phenotype is emerging, and recent hypothesis of hyperactivation of mTORC1 signaling might also open to targeted treatments, challenging an early diagnosis as of paramount importance.
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Affiliation(s)
- Marina Trivisano
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Manuel Rivera
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy; Departamento de Neuropediatria, Fleni, Montañeses 2325, C1428AQK Ciudad de Buenos Aires, Argentina
| | | | - Andrea Ciolfi
- Genetics and Rare Diseases Research Division, Bambino Gesù Children's Hospital, IRCSS, Rome, Italy
| | - Antonio Napolitano
- Neuroradiology Unit, Department of Imaging, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Chiara Pepi
- Child Neurology and Psychiatry Unit, Systems Medicine Department, Tor Vergata University, Via Montpellier 1, 00133 Rome, Italy
| | - Costanza Calabrese
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Maria Cristina Digilio
- Medical Genetics, Department of Pediatrics, Bambino Gesù Children's Hospital, IRCSS, Rome, Italy
| | - Marco Tartaglia
- Genetics and Rare Diseases Research Division, Bambino Gesù Children's Hospital, IRCSS, Rome, Italy
| | - Paolo Curatolo
- Child Neurology and Psychiatry Unit, Systems Medicine Department, Tor Vergata University, Via Montpellier 1, 00133 Rome, Italy
| | - Federico Vigevano
- Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Rome; Member of European Reference Network EpiCARE
| | - Nicola Specchio
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy; Member of European Reference Network EpiCARE.
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Papandreou A, Danti FR, Spaull R, Leuzzi V, Mctague A, Kurian MA. The expanding spectrum of movement disorders in genetic epilepsies. Dev Med Child Neurol 2020; 62:178-191. [PMID: 31784983 DOI: 10.1111/dmcn.14407] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/01/2019] [Indexed: 12/27/2022]
Abstract
An ever-increasing number of neurogenetic conditions presenting with both epilepsy and atypical movements are now recognized. These disorders within the 'genetic epilepsy-dyskinesia' spectrum are clinically and genetically heterogeneous. Increased clinical awareness is therefore necessary for a rational diagnostic approach. Furthermore, careful interpretation of genetic results is key to establishing the correct diagnosis and initiating disease-specific management strategies in a timely fashion. In this review we describe the spectrum of movement disorders associated with genetically determined epilepsies. We also propose diagnostic strategies and putative pathogenic mechanisms causing these complex syndromes associated with both seizures and atypical motor control. WHAT THIS PAPER ADDS: Implicated genes encode proteins with very diverse functions. Pathophysiological mechanisms by which epilepsy and movement disorder phenotypes manifest are often not clear. Early diagnosis of treatable disorders is essential and next generation sequencing may be required.
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Affiliation(s)
- Apostolos Papandreou
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Department of Neurology, Great Ormond Street Hospital, London, UK
| | - Federica Rachele Danti
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Department of Human Neuroscience, Unit of Child Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy
| | - Robert Spaull
- Department of Paediatric Neurology, Bristol Royal Hospital for Children, Bristol, UK
- Bristol Medical School, University of Bristol, Bristol, UK
| | - Vincenzo Leuzzi
- Department of Human Neuroscience, Unit of Child Neurology and Psychiatry, Sapienza University of Rome, Rome, Italy
| | - Amy Mctague
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Department of Neurology, Great Ormond Street Hospital, London, UK
| | - Manju A Kurian
- Molecular Neurosciences, Developmental Neurosciences Programme, UCL Great Ormond Street Institute of Child Health, London, UK
- Department of Neurology, Great Ormond Street Hospital, London, UK
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15
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Nakamura Y, Kato K, Tsuchida N, Matsumoto N, Takahashi Y, Saitoh S. Constitutive activation of mTORC1 signaling induced by biallelic loss-of-function mutations in SZT2 underlies a discernible neurodevelopmental disease. PLoS One 2019; 14:e0221482. [PMID: 31430354 PMCID: PMC6701784 DOI: 10.1371/journal.pone.0221482] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Accepted: 08/07/2019] [Indexed: 12/11/2022] Open
Abstract
There have been increasing number of reports of SZT2-related neurological diseases, the main symptoms of which are epilepsy, developmental delay, macrocephaly and a dysmorphic corpus callosum. SZT2 functions as a regulator of mechanistic target of rapamycin complex 1 (mTORC1) signaling in cultured human cell lines and mouse tissues. However, it remains to be determined whether mutations in SZT2 in human patients alter mTORC1 signaling. In this study, we aimed to investigate the functional consequence of biallelic SZT2 variants in Epstein-Barr virus-induced lymphoblastoid cell lines (LCLs) established from two patients with a typical SZT2-related neurodevelopmental disease. Increased phosphorylation of S6 kinase and S6 was identified in patient-derived cell lines under amino acid-starved condition, suggestive of constitutive hyperactivation of mTORC1 signaling. This result was validated by constitutive lysosomal localization of mTOR in patients’ LCLs. Furthermore, patients’ LCLs display an excessive response to slight amino acid stimulation. Our data suggest the loss-of-function nature of SZT2 mutations in the patients, and consequent hyperactivation of mTORC1 signaling in response to both amino acid starvation and stimulation in their LCLs. By these functional analyses, the pathogenicity of newly identified SZT2 variants can be determined, allowing for more detailed characterization of genotype-phenotype correlations.
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Affiliation(s)
- Yuji Nakamura
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Kohji Kato
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
- Department of Pediatrics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Naomi Tsuchida
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Yoshiyuki Takahashi
- Department of Pediatrics, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shinji Saitoh
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
- * E-mail:
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16
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Sun X, Zhong X, Li T. Novel SZT2 mutations in three patients with developmental and epileptic encephalopathies. Mol Genet Genomic Med 2019; 7:e926. [PMID: 31397114 PMCID: PMC6732301 DOI: 10.1002/mgg3.926] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 07/15/2019] [Accepted: 07/26/2019] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The seizure threshold 2 (SZT2) gene encodes a large, highly conserved protein that lowers seizure threshold and may also enhance epileptogenesis. In this study, three patients diagnosed with SZT2-related developmental and epileptic encephalopathies (DEEs) were reviewed aiming to expand knowledge of the genotype and phenotype of SZT2 mutations. METHODS Targeted next-generation sequencing was performed to identify pathogenic mutations in 205 cases with DEEs of unknown etiology. Detailed clinical and genetic data were collected from SZT2-associated patients. RESULTS Four novel mutations were found (c.1626 + 1G>A, c.5772dupA, c.4209C > A, c.7307_7308insG) in three patients. All the variants were inherited from their parents. Two patients were siblings and harbored the same mutations and presented developmental delay prior to the onset of seizures. All the individuals were diagnosed as DEEs, drug refractory epilepsy, and experienced status epilepticus (SE); one patient died of SE. One subject showed subependymal nodules as similar as those of tuberous sclerosis complex (TSC) in cranial magnetic resonance imaging (MRI). CONCLUSION Our results expand the genotype and phenotypes of SZT2-related DEEs, suggesting that SZT2 mutations play a role in developmental delay and epileptic encephalopathy, with high susceptibility to SE and relatively specific MRI findings.
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Affiliation(s)
- Xiaomin Sun
- Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China.,Key Laboratory of Pediatrics in Chongqing, Chongqing, China.,Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, China
| | - Xuefei Zhong
- Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China.,Key Laboratory of Pediatrics in Chongqing, Chongqing, China.,Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, China
| | - Tingsong Li
- Ministry of Education Key Laboratory of Child Development and Disorders, Children's Hospital of Chongqing Medical University, Chongqing, China.,Key Laboratory of Pediatrics in Chongqing, Chongqing, China.,Chongqing International Science and Technology Cooperation Center for Child Development and Disorders, Chongqing, China
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17
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Domingues FS, König E, Schwienbacher C, Volpato CB, Picard A, Cantaloni C, Mascalzoni D, Lackner P, Heimbach A, Hoffmann P, Stanzial F, Hicks AA, Parmeggiani L, Benedicenti F, Pellegrin S, Casara G, Pramstaller PP. Compound heterozygous SZT2 mutations in two siblings with early-onset epilepsy, intellectual disability and macrocephaly. Seizure 2019; 66:81-85. [PMID: 30818181 DOI: 10.1016/j.seizure.2018.12.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/02/2018] [Accepted: 12/22/2018] [Indexed: 01/22/2023] Open
Abstract
PURPOSE Mutations in SZT2 have been previously reported in several cases of early onset epilepsy and intellectual disability. In this study we investigate potential causal mutations in two male siblings affected by early onset epilepsy, intellectual disability and macrocephaly. METHODS We use family-based whole-exome sequencing to identify candidate variants. RESULTS We report the identification of two potential causal SZT2 mutations in compound heterozygous state. We observe considerable differences in the clinical phenotype severity of the two affected individuals. The cerebral MRI revealed no abnormalities in the older affected brother, while in the youngest one it revealed a right frontal polymicrogiria. Moreover, while good seizure control was achieved in the older affected individual the younger brother is affected by pharmacoresistant epilepsy, progressive spastic paraplegia, cortical myoclonus and a more severe intellectual disability. We also analyzed the relative location of the reported pathogenic mutations in the SZT2 protein. CONCLUSION Variable phenotypic expressivity is observed for this condition, while the location and type of mutations in SZT2 also has a potential impact on epilepsy severity. These findings extend our knowledge of epileptogenic conditions related to SZT2 and mTOR signaling.
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Affiliation(s)
- Francisco S Domingues
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy.
| | - Eva König
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy; Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - Christine Schwienbacher
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Claudia B Volpato
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Anne Picard
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Chiara Cantaloni
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Deborah Mascalzoni
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Peter Lackner
- Department of Biosciences, University of Salzburg, Salzburg, Austria
| | - André Heimbach
- NGS Core Facility, Life & Brain Center, University of Bonn, Bonn, Germany
| | - Per Hoffmann
- Human Genomics Research Group, Department of Biomedicine, University of Basel, Basel, Switzerland; Department of Genomics, Life & Brain Center, University of Bonn, Bonn, Germany
| | - Franco Stanzial
- Genetic Counseling Service, Department of Pediatrics, Regional Hospital of Bolzano, Bolzano, Italy
| | - Andrew A Hicks
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy
| | - Lucio Parmeggiani
- Child Neurology and Neurorehabilitation Unit, Department of Pediatrics, Regional Hospital of Bolzano, Bolzano, Italy
| | - Francesco Benedicenti
- Genetic Counseling Service, Department of Pediatrics, Regional Hospital of Bolzano, Bolzano, Italy
| | - Serena Pellegrin
- Child Neurology and Neurorehabilitation Unit, Department of Pediatrics, Regional Hospital of Bolzano, Bolzano, Italy
| | - Gianluca Casara
- Child Neurology and Neurorehabilitation Unit, Department of Pediatrics, Regional Hospital of Bolzano, Bolzano, Italy
| | - Peter P Pramstaller
- Institute for Biomedicine, Eurac Research, Affiliated Institute of the University of Lübeck, Bolzano, Italy; Department of Neurology, University of Lübeck, Lübeck, Germany
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18
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Imaizumi T, Kumakura A, Yamamoto-Shimojima K, Ondo Y, Yamamoto T. Identification of a rare homozygous SZT2 variant due to uniparental disomy in a patient with a neurodevelopmental disorder. Intractable Rare Dis Res 2018; 7:245-250. [PMID: 30560016 PMCID: PMC6290849 DOI: 10.5582/irdr.2018.01117] [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] [Indexed: 12/31/2022] Open
Abstract
Because biallelic SZT2 variants have been reported in patients with neurodevelopmental disorders associated with various degrees of developmental delay, intractable seizures, and distinctive features; this condition is recognized as an autosomal recessive disorder. Previously, eleven patients have been reported and most of them have compound heterozygous SZT2 variants, leading to premature termination. In these patients, all reported variants were unique and there were no common pathogenic variants identified. In this study, we identified a paternal uniparental disomy of chromosome 1 in a patient with a neurodevelopmental disorder associated with severe intellectual disability, intractable epilepsy, autistic features, distinctive features, and transient macrocephaly. This resulted in homozygous patterns through chromosome 1. Among the variants in chromosome 1, a rare SZT2 variant, NM_015284.3:c.6553C>T (p.Arg2185Trp), was selected as a powerful candidate variant in this patient. Although the clinical features of this patient are relatively milder than that reported previously, it may be derived from genetic heterogeneity. This is the first report of a homozygous missense SZT2 variant.
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Affiliation(s)
- Taichi Imaizumi
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
- Department of Pediatrics, St. Marianna University School of Medicine, Kawasaki, Japan
| | | | - Keiko Yamamoto-Shimojima
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
- Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan
| | - Yumko Ondo
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
| | - Toshiyuki Yamamoto
- Institute of Medical Genetics, Tokyo Women's Medical University, Tokyo, Japan
- Tokyo Women's Medical University Institute for Integrated Medical Sciences, Tokyo, Japan
- Address correspondence to:Professor Toshiyuki Yamamoto, Institute of Medical Genetics, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ward, Tokyo 162-8666, Japan. E-mail:
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19
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Uittenbogaard M, Gropman A, Brantner CA, Chiaramello A. Novel metabolic signatures of compound heterozygous Szt2 variants in a case of early-onset of epileptic encephalopathy. Clin Case Rep 2018; 6:2376-2384. [PMID: 30564332 PMCID: PMC6293145 DOI: 10.1002/ccr3.1868] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/25/2018] [Indexed: 01/06/2023] Open
Abstract
Our study reports the case of a patient with early onset of epileptic encephalopathy harboring compound heterozygous Szt2 variants. We provide the first evidence that these Szt2 variants impair mitochondrial energy metabolism. Our results shed light on their pathogenic molecular mechanism and clinical implications for brain development and disease progression.
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Affiliation(s)
- Martine Uittenbogaard
- Department of Anatomy and Regenerative Biology George Washington University School of Medicine and Health Sciences Washington District of Columbia
| | - Andrea Gropman
- Division of Neurogenetics and Developmental Pediatrics Children's National Medical Center Washington District of Columbia
| | - Christine A Brantner
- GW Nanofabrication and Imaging Center Office of the Vice President for Research George Washington University Washington District of Columbia
| | - Anne Chiaramello
- Department of Anatomy and Regenerative Biology George Washington University School of Medicine and Health Sciences Washington District of Columbia
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20
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Calhoun JD, Carvill GL. Unravelling the genetic architecture of autosomal recessive epilepsy in the genomic era. J Neurogenet 2018; 32:295-312. [PMID: 30247086 DOI: 10.1080/01677063.2018.1513509] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The technological advancement of next-generation sequencing has greatly accelerated the pace of variant discovery in epilepsy. Despite an initial focus on autosomal dominant epilepsy due to the tractable nature of variant discovery with trios under a de novo model, more and more variants are being reported in families with epilepsies consistent with autosomal recessive (AR) inheritance. In this review, we touch on the classical AR epilepsy variants such as the inborn errors of metabolism and malformations of cortical development. However, we also highlight recently reported genes that are being identified by next-generation sequencing approaches and online 'matchmaking' platforms. Syndromes mainly characterized by seizures and complex neurodevelopmental disorders comorbid with epilepsy are discussed as an example of the wide phenotypic spectrum associated with the AR epilepsies. We conclude with a foray into the future, from the application of whole-genome sequencing to identify elusive epilepsy variants, to the promise of precision medicine initiatives to provide novel targeted therapeutics specific to the individual based on their clinical genetic testing.
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Affiliation(s)
- Jeffrey D Calhoun
- a Department of Neurology , Northwestern University Feinberg School of Medicine , Chicago , IL , USA
| | - Gemma L Carvill
- a Department of Neurology , Northwestern University Feinberg School of Medicine , Chicago , IL , USA
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21
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Pizzino A, Whitehead M, Sabet Rasekh P, Murphy J, Helman G, Bloom M, Evans SH, Murnick JG, Conry J, Taft RJ, Simons C, Vanderver A, Adang LA. Mutations in SZT2 result in early-onset epileptic encephalopathy and leukoencephalopathy. Am J Med Genet A 2018; 176:1443-1448. [PMID: 29696782 DOI: 10.1002/ajmg.a.38717] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 02/13/2018] [Accepted: 03/28/2018] [Indexed: 11/06/2022]
Abstract
Early-onset epileptic encephalopathies (EOEEs) are a genetically heterogeneous collection of severe epilepsies often associated with psychomotor regression. Mutations in SZT2, a known seizure threshold regulator gene, are a newly identified cause of EOEE. We present an individual with EOEE, macrocephaly, and developmental regression with compound heterozygous mutations in SZT2 as identified by whole exome sequencing. Serial imaging characterized the novel finding of progressive loss of central myelination. This case expands our clinical understanding of the SZT2-phenotype and emphasizes the role of this gene in the diagnostic investigation for EOEE and leukoencephalopathies.
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Affiliation(s)
- Amy Pizzino
- Department of Neurology, Children's National Medical Center, Washington, DC
| | - Matthew Whitehead
- Department of Neuroradiology, The George Washington University School of Medicine, Washington, DC.,Department of Diagnostic Imaging and Radiology, Children's National Medical Center, Washington, DC
| | | | - Jennifer Murphy
- Undiagnosed Disease Program, National Human Genome Research Institute (NHGRI), Bethesda, Maryland
| | - Guy Helman
- Institute for Molecular Bioscience, University of Queensland, St. Lucia, Queensland, Australia
| | - Miriam Bloom
- Department of Pediatrics, Children's National Medical Center, Washington, DC
| | - Sarah H Evans
- Department of Neurology, Children's National Medical Center, Washington, DC
| | - John G Murnick
- Department of Diagnostic Imaging and Radiology, Children's National Medical Center, Washington, DC
| | - Joan Conry
- Department of Neurology, Children's National Medical Center, Washington, DC
| | - Ryan J Taft
- Undiagnosed Disease Program, National Human Genome Research Institute (NHGRI), Bethesda, Maryland.,Illumina, Inc., San Diego, California
| | - Cas Simons
- Undiagnosed Disease Program, National Human Genome Research Institute (NHGRI), Bethesda, Maryland
| | - Adeline Vanderver
- Department of Neurology, Children's National Medical Center, Washington, DC.,Center for Genetic Medicine Research, Children's National Medical Center, Washington, DC.,School of Medicine and Health Sciences, George Washington University, Washington, DC.,Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Laura A Adang
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
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22
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Nakamura Y, Togawa Y, Okuno Y, Muramatsu H, Nakabayashi K, Kuroki Y, Ieda D, Hori I, Negishi Y, Togawa T, Hattori A, Kojima S, Saitoh S. Biallelic mutations in SZT2 cause a discernible clinical entity with epilepsy, developmental delay, macrocephaly and a dysmorphic corpus callosum. Brain Dev 2018; 40:134-139. [PMID: 28893434 DOI: 10.1016/j.braindev.2017.08.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 08/01/2017] [Accepted: 08/19/2017] [Indexed: 11/25/2022]
Abstract
Mutations in SZT2 were first reported in 2013 as a cause of early-onset epileptic encephalopathy. Because only five reports have been published to date, the clinical features associated with SZT2 remain unclear. We herein report an additional patient with biallelic mutations in SZT2. The proband, a four-year-old girl, showed developmental delay and seizures from two years of age. Her seizures were not intractable and readily controlled by valproate. She showed mildly dysmorphic facies with macrocephaly, high forehead, and hypertelorism, and also had pectus carinatum. An EEG showed epileptic discharges which rarely occurred. A brain MRI revealed a short and thick corpus callosum. Whole-exome sequencing detected compound heterozygous biallelic mutations (c.8596dup (p.Tyr2866Leufs∗42) and c.2930-17_2930-3delinsCTCGTG) in SZT2, both of which were novel and predicted to be truncating. This case suggested a broad phenotypic spectrum arises from SZT2 mutations, forming a continuum from epileptic encephalopathy and severe developmental delay to mild intellectual disability without epilepsy. The characteristic thick and short corpus callosum observed in 7/8 cases with epilepsy, including the proband, but not in three non-syndromic cases, appears to be specific, and thus useful for indicating the possibility of SZT2 mutations. This feature has the potential to make loss of SZT2 a clinically discernible disorder despite a wide clinical spectrum.
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Affiliation(s)
- Yuji Nakamura
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Yasuko Togawa
- Department of Pediatrics, Toyohashi Municipal Hospital, Japan
| | - Yusuke Okuno
- Center for Advanced Medicine and Clinical Research, Nagoya University Hospital, Japan
| | - Hideki Muramatsu
- Department of Pediatrics, Nagoya University Graduate School of Medicine, Japan
| | - Kazuhiko Nakabayashi
- Department of Maternal-Fetal Biology, National Research Institute for Child Health and Development, Tokyo, Japan
| | - Yoko Kuroki
- Department of Genome Medicine, National Research Institute for Child Health and Development, Tokyo, Japan
| | - Daisuke Ieda
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Ikumi Hori
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Yutaka Negishi
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Takao Togawa
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Ayako Hattori
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan
| | - Seiji Kojima
- Department of Pediatrics, Nagoya University Graduate School of Medicine, Japan
| | - Shinji Saitoh
- Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, Japan.
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