PIGS WITH THE DOMINANT WHITE COAT COLOR PHENOTYPE CARRY A DUPLICATIONOF THE KIT GENE ENCODING THE MAST STEM CELL-GROWTH FACTOR-RECEPTOR/

Comparative mapping data suggested that the dominant white coat color in pigs may be due to a mutation in KIT which encodes the mast/stem ce ll growth factor receptor. We report here that dominant white pigs lac k melanocytes in the skin, as would be anticipated for a KIT mutation. We found a complete association between the dominant white mutation a nd a duplication of the KIT gene, or part of it, in samples of unrelat ed pigs representing six different breeds. The duplication was reveale d by single strand conformation polymorphism (SSCP) analysis and subse quent sequence analysis showing that white pigs transmitted two nonall elic KIT sequences. Quantitative Southern blot and quantitative PCR an alysis, as well as fluorescence in situ hybridization (FISH) analysis, confirmed the presence of a gene duplication in white pigs. FISH anal yses showed that KIT and the very closely linked gene encoding the pla telet-derived growth factor receptor (PDGFRA) are both located on the short arm of Chromosome (Chr) 8 at band 8p12. The result revealed an e xtremely low rate of recombination in the centromeric region of this c hromosome, since the closely linked (0.5 cM) serum albumin (ALB) locus has previously been in situ mapped to the long arm (8q12). Pig Chr 8 shares extensive conserved synteny with human Chr 4, but the gene orde r is rearranged.