We have observed that the frequency of D17S855 short alleles (139 bp and 141 bp) in individuals carrying BRCA1 germline mutations is higher than in controls (54% vs. 31%, p = 0.0004). By unambiguously establishing mutation/D17S855 phase in 18 BRCA1-positive families, we find that most (11 of 15 different mutations) BRCA1 defects are linked to chromosomes with short alleles (OR = 8.21, 95% CI 1.97-39.32, p = 0.0007). We suggest that BRCA1 mutations are not randomly distributed but clustered in a subset of BRCA1 alleles that can be identified by D17S855 genotyping. Further analysis involving a larger set of mutations and different populations are needed to clarify the relevance of this unexpected finding.
Copyright 2002 Wiley-Liss, Inc.