Holland, Paul W (2015-05). Identification of the Regions of the Bovine Genome Associated with Gray Coat Color in a Nellore-Angus Cross Population. Master's Thesis.
The genetics of coat color for cattle are important to breeders and breed associations because phenotypes of these animals are used for breed recognition and premiums or discounts can be given due to the phenotypes. The gene for gray coat color has been determined in other species, but not in cattle. Gray in cattle is known to be recessive based upon observed inheritance. The objective of this study was to identify the regions of the bovine genome associated with gray coat color in a population of Nellore-Angus crossbred cattle. Additionally, proportions of each color and spotting were of interest.
Animals (n = 1941) were classified into phenotypic color categories (i.e. red, black, gray, etc.). Proportions of each color group out of the population were determined, and the proportion of those phenotypes that have any form of spotting. Two genome-wide association analyses were conducted, one where phenotypically gray vs. not gray cattle were analyzed and another where cattle that were very light in color but had a reddish tinge were included as gray. Analyses used Bonferroni correction at ? = 0.05 (?/ntests = 1.49 x 10^-6). Analysis of gray vs. not gray yielded one significant SNP marker on BTA6 at a location of 68,059,441 bp (Praw = 9.69 x 10^-7, Padjusted = 0.032) (UMD_3.1, NCBI project 32899, Gen Bank GCA_000003055.3). For the analysis of gray and reddish tinged vs. not gray, there were 5 significant markers all on BTA6 forming a region from 62.93 Mb to 83.92 Mb (UMD_3.1, NCBI project 32899, Gen Bank GCA_000003055.3).The same SNP marker from the first analysis was present in the second, but had an increased significance (Praw = 1.50 x 10^-10, Padjusted = 5.02 x 10^-6). The region on BTA6 ruled out syntaxin-17 (STX17) on BTA8 and premelanosome protein (PMEL) on BTA5, previous gray candidate genes from other species, but includes genes such as v-kit Hardy-Zuckerman 4 feline sarcoma viral oncogene homolog (KIT), which is known to cause white coloration (spotting), and platelet-derived growth factor receptor alpha polypeptide (PDGFRA), the strongest candidate gene for the reddening in Nellore-Angus cattle, and corin serin pepsidase (CORIN), known for lighter coloration.