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Molecular screening for R138Q mutation in the podocin gene for focal segmental glomerulosclerosis (FSGS)

Introduction and Aims: A single nucleotide substitution of G to A at position 413 in the third exon of podocine gene (NPHS2), (R138Q), was described in the one third of the familial cases of nephrotic syndrome of FSGS (Boute et al. Nat Genet 2000 ; 24:349). A possibility of this mutation was also suggested for sporadic cases of idiopathic nephrotic syndrome resistent to glucocorticoids. Methods: We have designed a molecular, PCR-RFLP test that exploits the fact that G to A nucleotide substitution abolishes the cutting site of HaeIII restriction endonuclease. Thus, for a wild type sequence (GGCC)HaeIII would cut the amplified PCR products in two fragments of 63 and 107 bps. Mutated sequence (GACC) would remain uncut with the 170 bp PCR product. Results: In the pilot study we have screened 36 of adult patients (> 21yr of age at the presentation, range 21 – 80ys) who had primary FSGS with nonnephrotic and mostly nephrotic-range proteinuria. The PCR assay produced the expected 170bp amlicon of the NPHS2 gene.After digestion with HaeIII restriction endonuclease PCR amplicons of all patients examined were cut thus indicating the absence of mutation. Conclusions: When analysing the present finding one has to bear in mind that mutations at the other sites in the gene (several different mutations were described so far) are possible. Nevertheless, presented molecular test is simple and rapid thus applicable for screening for the R 138Q, the most frequent mutation of the podocin gene. Further testing in selected and larger population is waranted, since it might modify therapeuthic aproach in this patients.

podocin gene mutation; focal segmental glomerulosclerosis; molecular screening

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