Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2006
Publication Date: 1/3/2007
Citation: Mariasegaram, H., Chase, C.C., Chaparro, J.X., Olson, T.A., Brenneman, R.A., Niedz, R.P. 2007. The Slick Hair Coat Locus Maps to Bovine Chromosome 20 in Senepol Derived Cattle. Animal Genetics. 38:54-59. Interpretive Summary: The slick hair coat phenotype has been observed in tropical breeds of Bos taurus cattle in the New World, and has been studied in the Senepol and Carora cattle which possess very short, sleek hair coats. The slick hair phenotype has been found to be beneficial for heat tolerance in these breeds with body temperatures often 0.5 degrees Celsius lower for slick haired animals compared to their normal haired half-sibs, during hot summer days. A genome scan to map the slick hair gene was conducted in Senepol derived cattle. The results will facilitate efforts towards introgression of this gene into important Bos taurus breeds like the Angus and Charolais to enhance their adaptation to tropical environments. In the first experiment a heterozygous Senepol sire was selected that sired an equal number of slick and normal haired daughters from Holstein dams. A scan of the bovine genome using the DNA pooling strategy and typing over 300 microsatellite markers revealed that bovine chromosome 20 was the most likely candidate chromosome harboring the slick gene. This was followed by individual genotyping and interval mapping to confirm the results and to refine the location of the gene along the chromosome. A total of 14 microsatellite markers on bovine chromosome 20 were individually genotyped in two pedigrees (n=36) consisting of slick and normal haired cattle that represented both dairy and beef breeds. In this way, the gene was localized with high certainty to a specific region of bovine chromosome 20. By using additional microsatellite markers in this region, and genotyping in 6 more pedigrees (n=86), the slick locus was further fine mapped to the genomic region bound by two very tightly linked microsatellite markers. The mapping of the slick hair locus is the first step towards the eventual identification of the causative mutation that would constitute the definitive test for the slick hair coat phenotype. The strong association seen between the two closely positioned microsatellite markers on cattle chromosome 20 and the slick hair phenotype portends the possibility for marker assisted selection.
Technical Abstract: The ability to maintain normal temperatures during heat stress is an important attribute for cattle in the subtropics and tropics. Previous studies have shown that Senepol cattle and their crosses with the Holstein, Charolais and Angus breeds are as heat tolerant as Brahman cattle. This has been attributed to the slick hair coat of Senepol cattle, which is thought to be controlled by a single dominant gene. In this study, a genome scan using a DNA pooling strategy indicated that the slick locus is most likely on bovine chromosome 20 (BTA 20). Interval mapping confirmed the BTA 20 assignment and refined the location of the locus. In total, 14 microsatellite markers were individually genotyped in two pedigrees consisting of slick and normal haired cattle (n=36), representing both dairy and beef breeds. The maximum LOD score was 9.4 for a 4.4 cM support interval between markers DIK2416 and BM4107. By using additional microsatellite markers in this region, and genotyping in six more pedigrees (n=86), the slick locus was further localized to the DIK4835 - DIK2930 interval.