Haplotype of the C61G BRCA1 mutation in Polish and Jewish individuals.

Recurring mutations in the BRCA1 gene are noted in some populations and represent either founder mutations or a mutational hot spot. The C61G*BRCA1 (c.181T>G) missense mutation is a pathogenic one commonly reported in Polish individuals. A Jewish non-Ashkenazi family (of Italian ancestry) was found to carry this mutation, and the present study aimed at evaluating whether this mutation represents a founder mutation or a mutational hot spot. To that end, multilocus allelotyping using five markers intragenic to and flanking the BRCA1 gene spanning a genomic region of approximately 1.5 Mbp was carried out in that family and in 20 unrelated Polish C61G*BRCA1 mutation carriers. Phasing was done using affected and unaffected Jewish family members. The alleles that compose the pathogenic, mutation-carrying intragenic BRCA1 haplotype of the Jewish mutation carriers were detected in 18/20 Polish mutation carriers. The two flanking markers farthest away showed more diversity, between and even within Polish individuals. In conclusion, the *BRCA1 missense mutation is a founder mutation that can be detected in geographically related populations.