Chromosome-specific single-locus FISH probes allow anchorage of an 1800-marker integrated radiation-hybrid/linkage map of the domestic dog genome to all chromosomes

Abstract

We present here the first fully integrated, comprehensive map of the canine genome, incorporating detailed cytogenetic, radiation hybrid (RH), and meiotic information. We have mapped a collection of 266 chromosome-specific cosmid clones, each containing a microsatellite marker, to all 38 canine autosomes by fluorescence in situ hybridization (FISH). A 1500-marker RH map, comprising 1078 microsatellites, 320 dog gene markers, and 102 chromosome-specific markers, has been constructed using the RHDF5000-2 whole-genome radiation hybrid panel. Meiotic linkage analysis was performed, with at least one microsatellite marker from each dog autosome on a panel of reference families, allowing one meiotic linkage group to be anchored to all 38 dog autosomes. We present a karyotype in which each chromosome is identified by one meiotic linkage group and one or more RH groups. This updated integrated map, containing a total of 1800 markers, covers >90% of the dog genome. Positional selection of anchor clones enabled us, for the first time, to orientate nearly all of the integrated groups on each chromosome and to evaluate the extent of individual chromosome coverage in the integrated genome map. Finally, the inclusion of 320 dog genes into this integrated map enhances existing comparative mapping data between human and dog, and the 1000 mapped microsatellite markers constitute an invaluable tool with which to perform genome scanning studies on pedigrees of interest.

Figure 2

Multicolor fluorescence in situ hybridization of canine clones to dog chromosome 5 (CFA 5). The integrated RH and meiotic maps for CFA 5 are shown on the right hand side with their corresponding sizes noted below each map. Six clones were selected on the basis of their positions along the length of the RH map and are indicated in colored text. A seventh clone, SLC2A4, was selected on the basis of its position in the meiotic map. Each of the seven clones was labeled with one of the following five fluorochromes: Spectrum Green dUTP (green signal), Spectrum Orange dUTP (gold signal), Spectrum Red dUTP (red signal), DEAC (aqua signal), and Cy5 (pink signal). All seven clones were cohybridized by FISH to elongated dog chromosomes. The resulting FISH image of a DAPI-counterstained CFA 5 is shown in the middle of the figure, illustrating the hybridization signals of all seven clones, along with the assignment of each clone to the DAPI-banded ideogram of CFA 5 (Breen et al 1999a). On the far left is the enhanced DAPI-banded image of the same CFA 5 alongside the corresponding conserved human chromosome segments identified by Breen et al. (1999c).