TRPC6 mutations in children with steroid-resistant nephrotic syndrome and atypical phenotype

Clin J Am Soc Nephrol. 2011 Jul;6(7):1626-34. doi: 10.2215/CJN.07830910.

Abstract

Background and objectives: Mutations in the TRPC6 gene have been recently identified as the cause of late-onset autosomal-dominant focal segmental glomerulosclerosis (FSGS). To extend the screening, we analyzed TRPC6 in 33 Italian children with sporadic early-onset SRNS and three Italian families with adult-onset FSGS.

Design, setting, participants, & measurements: TRPC6 mutation analysis was performed through PCR and sequencing. The effects of the detected amino acid substitutions were analyzed by bioinformatics tools and functional in vitro studies. The expression levels of TRPC6 and nephrin proteins were evaluated by confocal microscopy.

Results: Three heterozygous missense mutations (c.374A>G_p.N125S, c.653A>T_p.H218L, c.2684G>T_p.R895L) were identified. The first new mutation, p.H218L, was found in a 18-year-old boy who presented a severe form of FSGS at the age of 8 years. The second, p.R895L, a new de novo mutation, was identified in a girl with collapsing glomerulosclerosis at the age of 2 years. The former mutation, p.N125S, was found in two siblings with early-onset steroid-resistant nephrotic syndrome (SRNS) at the ages of 4 and 14 years. Renal immunofluorescence revealed upregulated expression of TRPC6 and loss of nephrin in glomeruli. The intracellular calcium concentrations were significantly higher in the cells expressing all mutant TRPC6 channels compared with cells expressing wild-type TRPC6.

Conclusions: Our findings suggest that TRPC6 variants can also be detected in children with early-onset and sporadic SRNS (4 of 33 patients). Moreover, in one patient a new de novo TRPC6 mutation was associated with a rare severe form of childhood collapsing glomerulosclerosis with rapid progression to uremia.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Age of Onset
  • Amino Acid Sequence
  • Base Sequence
  • Calcium / metabolism
  • Case-Control Studies
  • Child
  • Child, Preschool
  • DNA Mutational Analysis
  • Drug Resistance*
  • Female
  • Fluorescent Antibody Technique
  • Genetic Predisposition to Disease
  • Glomerulosclerosis, Focal Segmental / drug therapy
  • Glomerulosclerosis, Focal Segmental / epidemiology
  • Glomerulosclerosis, Focal Segmental / genetics*
  • Glomerulosclerosis, Focal Segmental / metabolism
  • HEK293 Cells
  • Humans
  • Infant
  • Italy / epidemiology
  • Kidney / drug effects
  • Kidney / metabolism*
  • Male
  • Membrane Proteins / metabolism
  • Microscopy, Confocal
  • Molecular Sequence Data
  • Mutation, Missense*
  • Nephrotic Syndrome / drug therapy
  • Nephrotic Syndrome / epidemiology
  • Nephrotic Syndrome / genetics*
  • Nephrotic Syndrome / metabolism
  • Pedigree
  • Phenotype
  • Polymerase Chain Reaction
  • Risk Assessment
  • Risk Factors
  • Steroids / therapeutic use*
  • TRPC Cation Channels / genetics*
  • TRPC Cation Channels / metabolism
  • TRPC6 Cation Channel
  • Transfection

Substances

  • Membrane Proteins
  • Steroids
  • TRPC Cation Channels
  • TRPC6 Cation Channel
  • TRPC6 protein, human
  • nephrin
  • Calcium