Report of the International Equine Gene Mapping Workshop: male linkage map

The goal of the First International Equine Gene Mapping Workshop, held in 1 995, was the construction of a low density, male linkage map for the horse. For this purpose, the International Horse Reference Family Panel (IHRFP) w as established, consisting of 12 paternal half-sib families with 448 half-s ib offspring provided by 10 laboratories. Blood samples were collected and DNA extracted in each laboratory and sent to the Lexington laboratory (KY, USA) for dispatch in aliquots to 14 typing laboratories. Ln total, 161 mark ers (144 microsatellites, seven blood groups and 10 proteins) were tested f or all families for which the sire was heterozygous. Genealogies and typing data were sent for analysis to the INRA laboratory (Jouy-en-Josas, France) according to a specific format and entered into a database with input veri fication and output processes. Linkage analysis was performed with the CRIM AP program. Significant linkage was detected for 124 loci, of which 95 were unambiguously ordered using a multipoint analysis with an average spacing of 14.2 cM. These loci were distributed among 29 linkage groups. A more com prehensive analysis including synteny group data and FISH data suggested th at 26 autosomes out of 31 are covered. The complete map spans 936 cM.