Constitutional genomic instability of 9p23-24 in BRCA2 mutation carriers

Germ-line mutations in the BRCA2 gene account for a large proportion of familial breast cancer cases in females, and for the majority of familial breast cancers in males. Recent studies provide evidence for a role of the BRCA2 protein in the maintenance of genomic integrity by involvement in DNA repair and recombination. In order to identify genetic damage resulting from mutated BRCA2 in humans, we analyzed constitutional karyotypes of BRCA2 mutation carriers. FISH anlysis from lymphocytes of patients of breast cancer families with germ-line BRCA2 mutation revealed additional constitutional chromosomal alterations on 9p23-24. The rearrangements observed include inversions, duplications and amplifications. Additionally, a high level of random somatic chromosomal abnormalities on 9p23-24 has been shown. The 9p rearrangements are complex in all families analysed, showing that this chromosomal region has suffered a number of intrachromosomal recombinations. The topography of the 9p rearrangements can differ among family members, even within an individual that can have cell populations with different 9p rearrangements. Collectively, these results point to an association of mutant BRCA2 with genomic instability and gene alteration in 9p23-24, in at least a subset of BRCA2 mutation carriers.