A radiation hybrid transcript map of the mouse genome

Expressed-sequence tag (EST) maps are an adjunct to sequence-based analytic al methods of gene detection and localization for those species for which s uch data are available, and provide anchors for high-density homology and o rthology mapping in species for which large-scale sequencing has yet to be done(1). Species for which radiation hybrid-based transcript maps have been established include human(2), rat(3-5), mouse(6), dog(7), cat(8) and zebra fish(9,10). We have established a comprehensive first-generation-placement radiation hybrid map of the mouse consisting of 5,904 mapped markers (3,993 ESTs and 1,911 sequence-tagged sites (STSs)). The mapped ESTs, which often originate from small-EST clusters, are enriched for genes expressed during early mouse embryogenesis and are probably different from those localized in humans. We have confirmed by in situ hybridization that even singleton E STs, which are usually not retained for mapping studies, may represent bona fide transcribed sequences. Our studies on mouse chromosomes 12 and 14 ort hologous to human chromosome 14 show the power of our radiation hybrid map as a predictive tool for orthology mapping in humans.