Sequence-Ready Contig for the 1.4-cM Ductal Carcinoma in Situ Loss of Heterozygosity Region on Chromosome 8p22–p23
We report the construction of an ∼1.7-Mb sequence-ready YAC/BAC clone contig of 8p22–p23. This chromosomal region has been associated with frequent loss of heterozygosity (LOH) in breast, ovarian, prostate, head and neck, and liver cancer. We first constructed a meiotic linkage map for 8p to resolve previously reported conflicting map orders from the literature. The target region containing a putative tumor suppressor gene was defined by allelotyping 65 cases of sporadic ductal carcinoma in situ with 18 polymorphic markers from 8p. The minimal region of loss encompassed the interval between D8S520 and D8S261, and one tumor had loss of D8S550 only. We chose to begin physical mapping of this minimal LOH region by concentrating on the distal end, which includes D8S550. A fine-structure radiation hybrid map for the region that extends from D8S520 (distal) to D8S1759 (proximal) was prepared, followed by construction of a single, integrated YAC/BAC contig for the interval. The ∼1730-kb contig consists of 13 YACs and 27 BACs. Fifty-four sequence-tagged sites (STSs) developed from BAC insert end-sequences and 11 expressed sequence tags were localized within the contig by STS content mapping. In addition, four unique cDNA clones from the region were isolated and fully sequenced. This integrated YAC/BAC resource provides the starting point for transcription mapping, genomic sequencing, and positional cloning of this region.