title: Mutations in KCND3 cause spinocerebellar ataxia type 22.
abstract: OBJECTIVE
  To identify the causative gene in spinocerebellar ataxia (SCA) 22, an autosomal dominant cerebellar ataxia mapped to chromosome 1p21-q23.
  
  
  METHODS
  We previously characterized a large Chinese family with progressive ataxia designated SCA22, which overlaps with the locus of SCA19. The disease locus in a French family and an Ashkenazi Jewish American family was also mapped to this region. Members from all 3 families were enrolled. Whole exome sequencing was performed to identify candidate mutations, which were narrowed by linkage analysis and confirmed by Sanger sequencing and cosegregation analyses. Mutational analyses were also performed in 105 Chinese and 55 Japanese families with cerebellar ataxia. Mutant gene products were examined in a heterologous expression system to address the changes in protein localization and electrophysiological functions.
  
  
  RESULTS
  We identified heterozygous mutations in the voltage-gated potassium channel Kv4.3-encoding gene KCND3: an in-frame 3-nucleotide deletion c.679_681delTTC p.F227del in both the Chinese and French pedigrees, and a missense mutation c.1034G>T p.G345V in the Ashkenazi Jewish family. Direct sequencing of KCND3 further identified 3 mutations, c.1034G>T p.G345V, c.1013T>C p.V338E, and c.1130C>T p.T377M, in 3 Japanese kindreds. Immunofluorescence analyses revealed that the mutant p.F227del Kv4.3 subunits were retained in the cytoplasm, consistent with the lack of A-type K(+) channel conductance in whole cell patch-clamp recordings.
  
  
  CONCLUSIONS
  Our data identify the cause of SCA19/22 in patients of diverse ethnic origins as mutations in KCND3. These findings further emphasize the important role of ion channels as key regulators of neuronal excitability in the pathogenesis of cerebellar degeneration.
authors.affiliation: Department of Neurology, National Yang-Ming University School of Medicine, Taipei, Taiwan; Brain Research Center, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Yi-Chung
authors.initials: YC
authors.lastname: Lee
authors.forename: Alexandra
authors.initials: A
authors.lastname: Durr
authors.forename: Karen
authors.initials: K
authors.lastname: Majczenko
authors.forename: Yen-Hua
authors.initials: YH
authors.lastname: Huang
authors.forename: Yu-Chao
authors.initials: YC
authors.lastname: Liu
authors.forename: Cheng-Chang
authors.initials: CC
authors.lastname: Lien
authors.forename: Pei-Chien
authors.initials: PC
authors.lastname: Tsai
authors.forename: Yaeko
authors.initials: Y
authors.lastname: Ichikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Goto
authors.forename: Marie-Lorraine
authors.initials: ML
authors.lastname: Monin
authors.forename: Jun Z
authors.initials: JZ
authors.lastname: Li
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Chung
authors.forename: Emeline
authors.initials: E
authors.lastname: Mundwiller
authors.forename: Vikram
authors.initials: V
authors.lastname: Shakkottai
authors.forename: Tze-Tze
authors.initials: TT
authors.lastname: Liu
authors.forename: Christelle
authors.initials: C
authors.lastname: Tesson
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Lu
authors.forename: Alexis
authors.initials: A
authors.lastname: Brice
authors.forename: Shoji
authors.initials: S
authors.lastname: Tsuji
authors.forename: Margit
authors.initials: M
authors.lastname: Burmeister
authors.forename: Giovanni
authors.initials: G
authors.lastname: Stevanin
authors.forename: Bing-Wen
authors.initials: BW
authors.lastname: Soong
mesh_terms: D000293:Adolescent; D000328:Adult; D044466:Asian People / Q000235:genetics; D002878:Chromosomes, Human, Pair 1; D004252:DNA Mutational Analysis; D005192:Family Health; D005260:Female; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000235:genetics; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D018408:Patch-Clamp Techniques; D051672:Shal Potassium Channels / Q000235:genetics*; D013132:Spinocerebellar Degenerations / Q000235:genetics*; D014162:Transfection; D055815:Young Adult
chemical_list: C497021:KCND3 protein, human; D051672:Shal Potassium Channels; D049452:Green Fluorescent Proteins