Abstract
Germline mutations in the BRCA1 and BRCA2 genes are strong genetic factors for predispositions to breast, ovarian, and other related cancers. This report describes a family with a history of breast and ovarian cancers that harbored a novel BRCA1 germline mutation. A single nucleotide deletion in intron 20, namely c.5332+4delA, was detected in a 43-year-old patient with breast cancer. This mutation led to the skipping of exon 20, which in turn resulted in the production of a truncated BRCA1 protein that was 1773 amino acids in length. The mother of the proband had died due to ovarian cancer and had harbored the same germline mutation. Ectopically expressed mutant BRCA1 protein interacted with the BARD1 protein, but showed a reduced transcriptional function, as demonstrated by the expression of cyclin B1. This novel germline mutation in the BRCA1 gene caused familial breast and ovarian cancers.