High mutation detection rate in the COL4A5 collagen gene in suspected Alport syndrome using PCR and direct DNA sequencing.

Approximately 85% of patients with Alport syn- drome (hereditary nephritis) have been estimated to have mu- tations in the X chromosomab COL4AS collagen gene; the remaining cases are autosomal with mutations in the COL4A3 or COL4A4 genes located on chromosome 2. In the present work, the promoter sequence and previously unknown intron sequences flanking exons 2 and 37 of COL4AS were deter- mined. Furthermore, intron sequences flanking the other 49 exons were expanded from 35 to 190 to facilitate mutation analysis of the gene. Using this information, all S 1 exons and the promoter region were PCR-ampbified and sequenced from DNA of SO randomly chosen patients with suspected Alport syndrome. Mutations were found in 41 patients, giving a mu- tation detection rate of 82%. Retrospective analysis of clinical data revealed that two of the cases might be autosomal. Al- though it could not be determined whether the remaining seven cases (14%) were autosomab or X chromosome-linked, it is likely that some of them were autosomal. It is concluded that PCR amplification and direct DNA sequencing of the promoter