title: Impaired neuronal KCC2 function by biallelic SLC12A5 mutations in migrating focal seizures and severe developmental delay.
abstract: Epilepsy of infancy with migrating focal seizures (EIMFS) is one of the early-onset epileptic syndromes characterized by migrating polymorphous focal seizures. Whole exome sequencing (WES) in ten sporadic and one familial case of EIMFS revealed compound heterozygous SLC12A5 (encoding the neuronal K(+)-Cl(-) co-transporter KCC2) mutations in two families: c.279 + 1G > C causing skipping of exon 3 in the transcript (p.E50_Q93del) and c.572 C >T (p.A191V) in individuals 1 and 2, and c.967T > C (p.S323P) and c.1243 A > G (p.M415V) in individual 3. Another patient (individual 4) with migrating multifocal seizures and compound heterozygous mutations [c.953G > C (p.W318S) and c.2242_2244del (p.S748del)] was identified by searching WES data from 526 patients and SLC12A5-targeted resequencing data from 141 patients with infantile epilepsy. Gramicidin-perforated patch-clamp analysis demonstrated strongly suppressed Cl(-) extrusion function of E50_Q93del and M415V mutants, with mildly impaired function of A191V and S323P mutants. Cell surface expression levels of these KCC2 mutants were similar to wildtype KCC2. Heterologous expression of two KCC2 mutants, mimicking the patient status, produced a significantly greater intracellular Cl(-) level than with wildtype KCC2, but less than without KCC2. These data clearly demonstrated that partially disrupted neuronal Cl(-) extrusion, mediated by two types of differentially impaired KCC2 mutant in an individual, causes EIMFS.
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Hirotomo
authors.initials: H
authors.lastname: Saitsu
authors.affiliation: Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan.
authors.forename: Tenpei
authors.initials: T
authors.lastname: Akita
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Ohba
authors.affiliation: Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugai
authors.affiliation: Department of Genetics, Hospital Kuala Lumpur, Jalan Pahang, Kuala Lumpur 50586, Malaysia.
authors.forename: Winnie Peitee
authors.initials: WP
authors.lastname: Ong
authors.affiliation: Department of Pediatrics, Hokkaido University Graduate School of Medicine, North 15 West 7, Sapporo 060-8638, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Shiraishi
authors.affiliation: Department of Child Neurology, National Center Hospital, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi-cho, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Yuasa
authors.affiliation: Department of Pediatrics, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsumoto
authors.affiliation: Department of Pediatrics, Institute of Pediatrics, Hospital Kuala Lumpur, Jalan Pahang, Kuala Lumpur 50586, Malaysia.
authors.forename: Khoo Teik
authors.initials: KT
authors.lastname: Beng
authors.affiliation: Department of Pediatrics and Neonatology, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-Cho, Nagoya 467-8601, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Saitoh
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Miyatake
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Nakashima
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Miyake
authors.affiliation: Department of Pediatrics, Showa University School of Medicine, 1-5-8 Hatanodai, Tokyo 142-8666, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kato
authors.affiliation: Department of Neurophysiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Fukuda
authors.affiliation: Department of Human Genetics, Graduate School of Medicine, Yokohama City University, 3-9 Fukuura, Yokohama 236-0004, Japan.
authors.forename: Naomichi
authors.initials: N
authors.lastname: Matsumoto
mesh_terms: D000328:Adult; D001692:Biological Transport; D002675:Child, Preschool; D002712:Chlorides / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation; D020641:Polymorphism, Single Nucleotide; D012640:Seizures / Q000473:pathology* / Q000503:physiopathology*; D017384:Sequence Deletion; D027981:Symporters / Q000235:genetics* / Q000378:metabolism*; D055815:Young Adult; D000096922:K Cl- Cotransporters
chemical_list: D002712:Chlorides; D027981:Symporters; C000606816:SLC12A5 protein, human; D000096922:K Cl- Cotransporters