Clinical spectrum of SCN2A mutations expanding to Ohtahara syndrome
Kazuyuki Nakamura1, Mitsuhiro Kato, Hitoshi Osaka
1From 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.
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.
Related Concept Videos
01:21Huntington Disease l: Introduction
01:05Single Nucleotide Polymorphisms-SNPs
02:26Comparing Copy Number Variations and SNPs
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
01:19Cushing Syndrome II: Pathophysiology
01:43Sex-linked Disorders
02:18Alternative RNA Splicing
There are five types of alternative RNA splicing that vary in the ways the pre-mRNA segments are removed or retained in the mature mRNA. The first...