Genetic polymorphisms in Agouti signaling protein (ASIP) and melanocortin 1 receptor (MC1R) genes and their association with coat color in native Bulgarian sheep breeds.

Abstract

Sheep coat color is an important visual trait for breed differentiation and characterization. In some native sheep breeds, coat color is a patterned phenotype that is the basis of selection. The diversity of coat color provides an important model phenotype for exploring gene roles and studying gene mutations. The present study investigates the genetic polymorphisms in the Agouti signaling protein (ASIP) and melanocortin 1 receptor (MC1R) genes and their association with coat colour in native Bulgarian sheep breeds. A total of 247 individuals belonging to 7 native sheep breeds from 38 herds were genotyped for the ASIP and MC1R genes. Five single nucleotide polymorphisms (SNPs) were detected in the MC1R gene, and three haplotypes were identified in the studied sheep breeds. The MC1R dominant allele (E^D) allele could be the sole cause of fully pigmented sheep (either black or brown coat colour) in the Native Karnobatska population. However, in the population of Karakachanska and Cupper-red Shumenska breeds, the cause of pigmentation can be both E^D and recessive non-agouti (A^a) alleles. In the samples of the Patch-faced Maritza and Dubenska breeds, the E^D allele of the MC1R gene is absent, and therefore the fully pigmented and "patch-faced" phenotypes are due to the recessive A^a allele. Genetic mechanisms for white phenotypes exist to some extent in the White Maritza, Native Starazagorska and Dubenska breeds. However, the white phenotype in these breeds cannot be explained by a double copy of the ASIP allele alone. The results of this study provide new insights into the genetic causes of coat colour variation in populations of seven native Bulgarian sheep breeds. Further research is needed to elucidate the complex genetic mechanism of coat colour in native Bulgarian sheep breeds, particularly the role of the Agouti gene in coat colour expression. Therefore, the results of this study can be considered as a starting point for improving the management and conservation of genetic diversity of coat colour varieties in breeding programmes for native Bulgarian sheep breeds.