title: New TRPC6 gain-of-function mutation in a non-consanguineous Dutch family with late-onset focal segmental glomerulosclerosis.
abstract: BACKGROUND
  Focal segmental glomerulosclerosis (FSGS) is a leading cause of steroid-resistant nephrotic syndrome. Hereditary FSGS is frequently caused by mutations in important structural podocyte proteins, including the slit diaphragm-associated transient receptor potential channel C6 (TRPC6).
  
  
  METHODS
  In five patients with biopsy-proven autosomal-dominant FSGS from five different Dutch families, all 13 exons of TRPC6 were sequenced. Upon identification of a novel TRPC6 sequence variant, the resultant amino acid change was introduced in the wild-type TRPC6 protein and functionally tested using patch-clamp analyses and cell-surface biotinylation experiments.
  
  
  RESULTS
  None of the previously described TRPC6 mutations were found in our cohort. In one family, we identified a novel c.524G>A sequence variant resulting in a p.Arg175Gln (R175Q) substitution in the TRPC6 protein. This sequence variant was absent in 449 control subjects and from public SNP databases. The mutation was located in the third ankyrin repeat domain (ANK3) in the cytoplasmic N-tail of TRPC6, important for protein-protein interaction and regulation of ion channel activity. Patch-clamp analyses of the mutant channel indeed showed an increased TRPC6 channel-mediated current. However, cell-surface expression of the mutant channel was not increased.
  
  
  CONCLUSIONS
  We identified a novel TRPC6 p.Arg175Gln gain-of-function mutation that shows increased TRPC6-mediated current, which is not due to altered cell-surface expression. This is the first mutation identified in ANK3 of the TRPC6 N-tail and is most likely responsible for the late-onset autosomal dominant FSGS in this family.
authors.affiliation: Department of Nephrology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Hofstra
authors.forename: Sergio
authors.initials: S
authors.lastname: Lainez
authors.forename: Willie H M
authors.initials: WH
authors.lastname: van Kuijk
authors.forename: Jeroen
authors.initials: J
authors.lastname: Schoots
authors.forename: Marijke P A
authors.initials: MP
authors.lastname: Baltissen
authors.forename: Lies H
authors.initials: LH
authors.lastname: Hoefsloot
authors.forename: Nine V A M
authors.initials: NV
authors.lastname: Knoers
authors.forename: Jo H M
authors.initials: JH
authors.lastname: Berden
authors.forename: René J M
authors.initials: RJ
authors.lastname: Bindels
authors.forename: Johan
authors.initials: J
authors.lastname: van der Vlag
authors.forename: Joost G J
authors.initials: JG
authors.lastname: Hoenderop
authors.forename: Jack F M
authors.initials: JF
authors.lastname: Wetzels
authors.forename: Tom
authors.initials: T
authors.lastname: Nijenhuis
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000595:Amino Acid Sequence; D002675:Child, Preschool; D003241:Consanguinity; D004594:Electrophysiology; D005190:Family; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D005923:Glomerulosclerosis, Focal Segmental / Q000209:etiology*; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D009426:Netherlands; D010375:Pedigree; D011379:Prognosis; D017386:Sequence Homology, Amino Acid; D050052:TRPC Cation Channels / Q000235:genetics*; D000074287:TRPC6 Cation Channel; D013997:Time Factors
chemical_list: D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human
keywords: TRPC6; focal segmental glomerulosclerosis; podocyte; proteinuria