title: TRPC6 mutations in children with steroid-resistant nephrotic syndrome and atypical phenotype.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
authors: Department of Biomedical Sciences, University of Foggia, Viale Pinto, 1, 71100 Foggia, Italy. l.gesualdo@unifg.it.
authors: Maddalena
authors: M
authors: Gigante
authors: Gianluca
authors: G
authors: Caridi
authors: Eustacchio
authors: E
authors: Montemurno
authors: Mario
authors: M
authors: Soccio
authors: Maria
authors: M
authors: d'Apolito
authors: Giuseppina
authors: G
authors: Cerullo
authors: Filippo
authors: F
authors: Aucella
authors: Annalisa
authors: A
authors: Schirinzi
authors: Francesco
authors: F
authors: Emma
authors: Laura
authors: L
authors: Massella
authors: Giovanni
authors: G
authors: Messina
authors: Tommaso
authors: T
authors: De Palo
authors: Elena
authors: E
authors: Ranieri
authors: Gian Marco
authors: GM
authors: Ghiggeri
authors: Loreto
authors: L
authors: Gesualdo
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D000595:Amino Acid Sequence; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004351:Drug Resistance; D005260:Female; D005455:Fluorescent Antibody Technique; D020022:Genetic Predisposition to Disease; D005923:Glomerulosclerosis, Focal Segmental / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007223:Infant; D007558:Italy / Q000453:epidemiology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009404:Nephrotic Syndrome / Q000188:drug therapy / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism; D010375:Pedigree; D010641:Phenotype; D016133:Polymerase Chain Reaction; D018570:Risk Assessment; D012307:Risk Factors; D013256:Steroids / Q000627:therapeutic use*; D050052:TRPC Cation Channels / Q000235:genetics* / Q000378:metabolism; D000074287:TRPC6 Cation Channel; D014162:Transfection
chemical_list: D008565:Membrane Proteins; D013256:Steroids; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C113267:nephrin; D002118:Calcium