Seven novel mutations of the PKD2 gene in families with autosomal dominant polycystic kidney disease

Background. Autosomal dominant polycystic kidney disease (ADPKD) is genetically heterogeneous, with at least three chromosomal loci accounting for the disease. Mutations in the PKD2 gene on the long arm of chromosome 4 are expected to be responsible for approximately 15% of cases of ADPKD. Methods. We report a systematic screening for mutations covering the 15 exons of the PKD2 gene in eight unrelated families with ADPKD type 2, using the heteroduplex technique. Results. Seven novel mutations were identified and characterized that, together with the previously described changes, amount to a detection rate of 85% in the population studied. The newly described mutations are two nonsense mutations, a 1 bp deletion, a 1 bp insertion, a mutation that involves both a substitution and a deletion (2511AG→C), a complex mutation in exon 6 consisting of a simultaneous 7 bp inversion and a 4 bp deletion, and the last one is a G→C transversion that may be a missense mutation. Most of these mutations are expected to lead to the formation of shorter truncated proteins lacking the carboxyl terminus of PKD2. We have also characterized a frequent polymorphism, Arg-Pro, at codon 28 in this gene. The clinical features of these PKD2 patients are similar to the previously described, with the mean age of end-stage renal disease being 75.5 years (SE ± 3.8 years). Conclusions. Our results confirm that many different mutations are likely to be responsible for the disease and that most pathogenic defects probably are point or small changes in the coding region of the gene.