Zoo-FISH delineates conserved chromosomal segments in horse and man

Human chromosome specific libraries (CSLs) were individually applied to equine metaphase chromosomes using the fluorescence in situ hybridization (FISH) technique. All CSLs, except Y, showed painting signals on one or several horse chromosomes. In total 43 conserved chromosomal segments were painted. Homoeology could not, however, be detected for some segments of the equine genome. This is most likely related to the very weak signals displayed by some libraries, rather than to the absence of similarity with the human genome. In spite of divergence from the human genome, dated 70-80 million years ago, a fairly high degree of synteny conservation was observed. In seven cases, whole chromosome synteny was detected between the two species. The comparative painting results agreed completely with the limited gene mapping data available in horses, and also enabled us provisionally to assign one linkage group (U2) and one syntenic group (NP, MPI, IDH2) to specific equine chromosomes. Chromosomal assignments of three other syntenic groups are also proposed. The findings of this study will be of significant use in the expansion of the hitherto poorly developed equine gene map.