title: Mutations in potassium channel kcnd3 cause spinocerebellar ataxia type 19.
abstract: OBJECTIVE
  To identify the causative gene for the neurodegenerative disorder spinocerebellar ataxia type 19 (SCA19) located on chromosomal region 1p21-q21.
  
  
  METHODS
  Exome sequencing was used to identify the causal mutation in a large SCA19 family. We then screened 230 ataxia families for mutations located in the same gene (KCND3, also known as Kv4.3) using high-resolution melting. SCA19 brain autopsy material was evaluated, and in vitro experiments using ectopic expression of wild-type and mutant Kv4.3 were used to study protein localization, stability, and channel activity by patch-clamping.
  
  
  RESULTS
  We detected a T352P mutation in the third extracellular loop of the voltage-gated potassium channel KCND3 that cosegregated with the disease phenotype in our original family. We identified 2 more novel missense mutations in the channel pore (M373I) and the S6 transmembrane domain (S390N) in 2 other ataxia families. T352P cerebellar autopsy material showed severe Purkinje cell degeneration, with abnormal intracellular accumulation and reduced protein levels of Kv4.3 in their soma. Ectopic expression of all mutant proteins in HeLa cells revealed retention in the endoplasmic reticulum and enhanced protein instability, in contrast to wild-type Kv4.3 that was localized on the plasma membrane. The regulatory β subunit Kv channel interacting protein 2 was able to rescue the membrane localization and the stability of 2 of the 3 mutant Kv4.3 complexes. However, this either did not restore the channel function of the membrane-located mutant Kv4.3 complexes or restored it only partially.
  
  
  CONCLUSIONS
  KCND3 mutations cause SCA19 by impaired protein maturation and/or reduced channel function.
authors.affiliation: Department of Genetics, University of Groningen, University Medical Center Groningen, Groningen.
authors.forename: Anna
authors.initials: A
authors.lastname: Duarri
authors.forename: Justyna
authors.initials: J
authors.lastname: Jezierska
authors.forename: Michiel
authors.initials: M
authors.lastname: Fokkens
authors.forename: Michel
authors.initials: M
authors.lastname: Meijer
authors.forename: Helenius J
authors.initials: HJ
authors.lastname: Schelhaas
authors.forename: Wilfred F A
authors.initials: WF
authors.lastname: den Dunnen
authors.forename: Freerk
authors.initials: F
authors.lastname: van Dijk
authors.forename: Corien
authors.initials: C
authors.lastname: Verschuuren-Bemelmans
authors.forename: Gerard
authors.initials: G
authors.lastname: Hageman
authors.forename: Pieter
authors.initials: P
authors.lastname: van de Vlies
authors.forename: Benno
authors.initials: B
authors.lastname: Küsters
authors.forename: Bart P
authors.initials: BP
authors.lastname: van de Warrenburg
authors.forename: Berry
authors.initials: B
authors.lastname: Kremer
authors.forename: Cisca
authors.initials: C
authors.lastname: Wijmenga
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Sinke
authors.forename: Morris A
authors.initials: MA
authors.lastname: Swertz
authors.forename: Harm H
authors.initials: HH
authors.lastname: Kampinga
authors.forename: Erik
authors.initials: E
authors.lastname: Boddeke
authors.forename: Dineke S
authors.initials: DS
authors.lastname: Verbeek
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology; D016022:Case-Control Studies; D047369:Chromatin Immunoprecipitation; D003513:Cycloheximide / Q000494:pharmacology; D004252:DNA Mutational Analysis; D018450:Disease Progression; D005192:Family Health; D005260:Female; D056726:Genetic Association Studies; D020022:Genetic Predisposition to Disease; D005838:Genotype; D057809:HEK293 Cells / Q000378:metabolism; D006367:HeLa Cells / Q000473:pathology; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000235:genetics; D020125:Mutation, Missense / Q000235:genetics*; D018408:Patch-Clamp Techniques; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051672:Shal Potassium Channels / Q000235:genetics*; D016622:Silver Staining; D013132:Spinocerebellar Degenerations / Q000235:genetics* / Q000473:pathology; D013997:Time Factors; D014162:Transfection
chemical_list: D008164:Luminescent Proteins; D011500:Protein Synthesis Inhibitors; D051672:Shal Potassium Channels; D003513:Cycloheximide