Kazuyuki Nakamura1, Mitsuhiro Kato, Hitoshi Osaka, Sumimasa Yamashita, Eiji Nakagawa, Kazuhiro Haginoya, Jun Tohyama, Mitsuko Okuda, Takahito Wada, Shuichi Shimakawa, Katsumi Imai, Saoko Takeshita, Hisako Ishiwata, Dorit Lev, Tally Lerman-Sagie, David E Cervantes-Barragán, Camilo E Villarroel, Masaharu Ohfu, Karin Writzl, Barbara Gnidovec Strazisar, Shinichi Hirabayashi, David Chitayat, Diane Myles Reid, Kiyomi Nishiyama, Hirofumi Kodera, Mitsuko Nakashima, Yoshinori Tsurusaki, Noriko Miyake, Kiyoshi Hayasaka, Naomichi Matsumoto, Hirotomo Saitsu. 1. From the Department of Human Genetics (K. Nakamura, K. Nishiyama, H.K., M.N., Y.T., N. Miyake, N. Matsumoto, H.S.), Yokohama City University Graduate School of Medicine, Yokohama; Department of Pediatrics (K. Nakamura, M.K., K. Hayasaka), Yamagata University Faculty of Medicine, Yamagata; Division of Neurology (H.O., S.Y., M. Okuda, T.W.), Clinical Research Institute, Kanagawa Children's Medical Center, Yokohama; Department of Child Neurology (E.N.), National Center Hospital, National Center of Neurology and Psychiatry, Tokyo; Department of Pediatric Neurology (K. Haginoya), Takuto Rehabilitation Center for Children, Sendai; Department of Pediatrics (J.T.), Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata; Department of Pediatrics (S.S.), Osaka Medical College Hospital, Osaka; National Epilepsy Center (K.I.), Shizuoka Institute of Epilepsy and Neurological Disorders, Shizuoka; Department of Pediatrics (S.T.), Yokohama City University Medical Center, Yokohama; Department of Pediatrics (H.I.), Tokyo Metropolitan Bokuto Hospital, Tokyo, Japan; Metabolic Neurogenetic Clinic (D.L., T.L.-S.), Wolfson Medical Center, Holon, Israel; Department of Human Genetics (D.E.C.-B., C.E.V.), National Institute of Pediatrics, Mexico City, Mexico; Division of Child Neurology (M. Ohfu), Okinawa Nanbu Medical Center and Children's Medical Center, Okinawa, Japan; Institute of Medical Genetics (K.W.), University Medical Center Ljubljana; Department of Child, Adolescent and Developmental Neurology (B.G.S.), University Children's Hospital, Ljubljana, Slovenia; Department of Neurology (S.H.), Nagano Children's Hospital, Nagano, Japan; Department of Obstetrics and Gynecology (D.C.), The Prenatal Diagnosis and Medical Genetics Program, Mount Sinai Hospital, University of Toronto; and Division of Clinical and Metabolic Genetics (D.C., D.M.R.), The Hospital for Sick Children, University of Toronto, Canada.
Abstract
OBJECTIVE: We aimed to investigate the possible association between SCN2A mutations and early-onset epileptic encephalopathies (EOEEs). METHODS: We recruited a total of 328 patients with EOEE, including 67 patients with Ohtahara syndrome (OS) and 150 with West syndrome. SCN2A mutations were examined using high resolution melt analysis or whole exome sequencing. RESULTS: We found 14 novel SCN2A missense mutations in 15 patients: 9 of 67 OS cases (13.4%), 1 of 150 West syndrome cases (0.67%), and 5 of 111 with unclassified EOEEs (4.5%). Twelve of the 14 mutations were confirmed as de novo, and all mutations were absent in 212 control exomes. A de novo mosaic mutation (c.3976G>C) with a mutant allele frequency of 18% was detected in one patient. One mutation (c.634A>G) was found in transcript variant 3, which is a neonatal isoform. All 9 mutations in patients with OS were located in linker regions between 2 transmembrane segments. In 7 of the 9 patients with OS, EEG findings transitioned from suppression-burst pattern to hypsarrhythmia. All 15 of the patients with novel SCN2A missense mutations had intractable seizures; 3 of them were seizure-free at the last medical examination. All patients showed severe developmental delay. CONCLUSIONS: Our study confirmed that SCN2A mutations are an important genetic cause of OS. Given the wide clinical spectrum associated with SCN2A mutations, genetic testing for SCN2A should be considered for children with different epileptic conditions.
OBJECTIVE: We aimed to investigate the possible association between SCN2A mutations and early-onset epileptic encephalopathies (EOEEs). METHODS: We recruited a total of 328 patients with EOEE, including 67 patients with Ohtahara syndrome (OS) and 150 with West syndrome. SCN2A mutations were examined using high resolution melt analysis or whole exome sequencing. RESULTS: We found 14 novel SCN2A missense mutations in 15 patients: 9 of 67 OS cases (13.4%), 1 of 150 West syndrome cases (0.67%), and 5 of 111 with unclassified EOEEs (4.5%). Twelve of the 14 mutations were confirmed as de novo, and all mutations were absent in 212 control exomes. A de novo mosaic mutation (c.3976G>C) with a mutant allele frequency of 18% was detected in one patient. One mutation (c.634A>G) was found in transcript variant 3, which is a neonatal isoform. All 9 mutations in patients with OS were located in linker regions between 2 transmembrane segments. In 7 of the 9 patients with OS, EEG findings transitioned from suppression-burst pattern to hypsarrhythmia. All 15 of the patients with novel SCN2A missense mutations had intractable seizures; 3 of them were seizure-free at the last medical examination. All patients showed severe developmental delay. CONCLUSIONS: Our study confirmed that SCN2A mutations are an important genetic cause of OS. Given the wide clinical spectrum associated with SCN2A mutations, genetic testing for SCN2A should be considered for children with different epileptic conditions.
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