Parallel radiation hybrid mapping: a powerful tool for high-resolution genomic comparison

Abstract

Comparative gene mapping in mammals typically involves identification of segments of conserved synteny in diverse genomes. The development of maps that permit comparison of gene order within conserved synteny has not advanced beyond the mouse map that takes advantage of linkage analysis in interspecific backcrosses. Radiation hybrid (RH) mapping provides a powerful tool for determining order of genes in genomes for which gene-based linkage mapping is impractical. Comparative RH mapping of 24 orthologous genes in this study revealed internal structural rearrangements between human chromosome 17 (HSA17) and bovine chromosome 19 (BTA19), two chromosomes known previously to be conserved completely and exclusively at level of synteny. Only six of the 24 genes had been previously ordered on the human G3 RH map. The use of the G3 panel to map the other 18, however, produced parallel RH maps for comparison of gene order at a resolution of <5 Mb on the bovine linkage map and from 1 to 3 Mb in the human physical map.

Figure 1

Comprehensive RH map of BTA chromosome 19. (Red) Framework markers ordered at odds >1000:1. (Green) Expressed genes and ESTs. Map units are cRays₅₀₀₀.

Figure 2

Parallel RH maps of BTA19 and HSA17. (Blue) Framework markers. The comparative RH map was divided into four regions with three breakpoints on each chromosome. Not only are the positions of region I (red) and region II (blue) inverted between human and bovine, but the gene orders within the two regions are also shuffled. (Green) Region III has the same gene order between human and cattle. The gene orders in region IV (black) between human and cattle are inverted.