DETECTION OF 2 DIFFERENT NONSENSE MUTATIONS IN EXON-44 OF THE PKD1 GENE IN 2 UNRELATED ITALIAN FAMILIES WITH SEVERE AUTOSOMAL-DOMINANT POLYCYSTIC KIDNEY-DISEASE

Sixty-seven Italian patients with autosomal dominant polycystic kidney disease (ADPKD) were screened for mutations in the PKD1 gene. We used PCR, heteroduplex and single-strand conformation polymorphism DNA ana lysis, and automated DNA sequencing for exons 35, 36, 38, 44 and 45. W e detected abnormal heteroduplexes in affected individuals from two un related families with clinically severe ADPKD phenotype. These changes were absent in other, unaffected members, as well as in the probands of the other families studied. DNA sequencing revealed in both cases d ifferent C to T transitions in exon 44, which created premature stop c odons. Both mutations altered restriction sites, and the abnormal patt erns were observed in all the affected family members. RT-PCR performe d on lymphocyte mRNA showed that both the mutant and the normal transc ript are represented. To our knowledge these are the first nonsense mu tations described in the PKD1 gene.