Plant & Animal Genome IX Conference

Workshop: Coat Color
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IDENTIFICATION OF THE GENE RESPONSIBLE FOR THE APPALOOSA SPOTTING PATTERNS.

University of Kentucky, Department of Veterinary Science, 108 Maxwell H. Gluck Equine Research Center, Lexington, KY 40546, USA

The Appaloosa breed of horse is known for its characteristic white spotting patterns, known as the leopard complex. There are 9 different patterns characterized to date: few spot leopard, snow cap, leopard, blanket, blanket with spots, varnish roan, snowflake, frosted, speckled, and mottled patterns. Breeding studies have indicated that a single dominant gene (Lp) is responsible for all of these patterns. Comparison with other species suggests two candidate genes for the leopard complex, namely, KIT and itĘs ligand MGF. In mice, pigs, human, and cattle mutations within these genes are responsible for pigmentation disorders that result in white spotting patterns. To evaluate whether either of these genes are homologous to Lp, linkage analyses were performed. A Taq I polymorphism identified within the KIT gene of the horse was uninformative in 8 appaloosa half sib families. Therefore we tested microsatellite markers closely linked to KIT. This linkage study rejected linkage and indicated that KIT was not responsible for Lp (Z= -5.3, q=.05 for ASB23 and Lp). No polymorphism is reported for MGF. MGF is known to be on horse chromosome 28 so linkage analyses were undertaken with syntenic markers. The results were inconclusive due to the number of informative offspring. Consequently, current work is directed toward discovery of additional genetic markers within or closely linked to MGF.