Implications of a novel cryptic splice site in the BRCA1 gene.

This study was designed to determine the significance of a single intronic base change (IVS5-12 G-->A) found in a family with a history of breast cancer. This change is predicted to form a cryptic splice site resulting in the addition of 11 nucleotides to the BRCA1 transcript. The BRCA1 gene of the relatives and control individuals was sequenced and analyzed using RT-PCR, ASO hybridization, and size fractionation. All patients showed an 11 nucleotide insert at the intron 5/exon 6 boundary. This variant is likely to form a short protein product incapable of the hypothesized tumor suppressor functions of the BRCA1 gene. This information is important for providing counseling for families with this cryptic splice site and a family history of breast cancer.