A contiguous 3-Mb sequence-ready map in the S3-MX region on 21q22.2 based on high-throughput nonisotopic library screenings

Progress in complete genomic sequencing of human chromosome 21 relies on th e construction of high-quality bacterial clone maps spanning large chromoso mal regions. To achieve this goal, we have applied a strategy based on nonr adioactive hybridizations to contig building. A contiguous sequence-ready m ap was constructed in the Down syndrome congenital heart disease [DS-CHD] r egion in 21q22.2, as a framework For large-scale genomic sequencing and pos itional candidate gene approach. Contig assembly was performed essentially by high throughput nonisotopic screenings of genomic libraries, prior to cl one validation by (1) restriction digest fingerprinting (2) STS analysis, ( 3) Southern hybridizations, and (4) FISH analysis. The contig contains a to tal of 50 STSs, of which 13 were newly isolated. A minimum tiling path (MTP ) was subsequently defined that consists of 20 PACs, 2 BACs, and 5 cosmids covering 3 Mb between D21S3 and MX1. Gene distribution in the region includ es 9 known genes (c21-LRP, WRB, SH3BGR, HMG14, PCP4, DSCAM, MX2, MX1, and T MPRSS2) and 14 new additional gene signatures consisting of cDNA selection products and ESTs. Forthcoming genomic sequence information will unravel th e structural organization of potential candidate genes involved in specific features of Down syndrome pathogenesis.