Year: 2025
Type: article
Abstract: Dexter cattle are genotyped for variants in the melanocortin 1 receptor (MC1R) gene, which determines black (ED) or red (E+ or e) coat color, as well as for a previously identified Dexter-specific variant of tyrosinase related protein 1 (TYRP1) that dilutes black to dun. Dexter cattle lacking the dun TYRP1 recessive genotype (bb) have been reported with an unexpected dark dun/chocolate (CD) or light dun/cream (CL) coat color. These unclassified coat colors occur at low frequency within the current Dexter cattle population. Based on observed inheritance patterns, we hypothesized a novel recessive genotype is causative of CD on a black background and CL on a red background. Whole genome sequence (WGS) data were collected from three chocolate animals, one cream animal, and one black calf of a chocolate dam. Data were mapped to the UCD-ARS1.2 genome and variants called. Combining these genotypes with those of 226 multibreed control cattle, a SnpSift case control analysis was conducted. 161 genomic variants fit the proposed hypothesis of homozygous recessive inheritance and were located within a 1.8 Mb segment of Chromosome 20. Two of those variants, when queried against a WGS database of over 5,500 cattle, were not present in other cattle. Only one of those variants had a predicted impact on gene function. The identified missense variant was in the solute carrier family 45 member 2 (SLC45A2) gene. DNA from over 190 Dexter cattle samples were screened by Sanger sequencing for the candidate SLC45A2 variant, as well as genotyped for known variation in MC1R, and TYRP1. Supporting our hypothesis, all cattle expressing the CL phenotype had two copies of the SLC45A2 variant on a red background and expressed the CD phenotype on a black background. There was no apparent coat color change in cattle heterozygous for the SLC45A2 variant, confirming a recessive mode of inheritance. The SLC45A2 (membrane-associated transporter protein; MATP and absent in melanoma 1; AIM1) protein has previously been shown to regulate coat, eye, and skin color in multiple species, including cattle, humans, horses, and mice. SLC45A2 plays a role in neutralizing pH of melanosomes to promote tyrosinase activity during stages III-IV of melanogenesis. An amino acid change in the SLC45A2 protein resulting from this mutation could potentially create an acidic environment, suppressing eumelanin synthesis. At present, no adverse consequences associated with this SLC45A2 variant in Dexter cattle have been identified. Testing for the SLC45A2 variant in Dexter cattle can be a valuable resource for Dexter breeders interested in coat color.
Source: Journal of Animal Science
Authors: Anna M Fuller, Jessica L Petersen
Institution: University of Nebraska–Lincoln
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W4414831319
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