Regiões genômicas associadas à variação da coloração da pelagem em bovinos da raça gir

Abstract

In Brazil, the Zebu breeds represent more than 80% of the cattle herd, with the Gir being one of the breeds of great importance, mainly for dairy production. The breed has twelve different coat color phenotypes (red, yellow, choker red, choker yellow, calico red, calico yellow, red calico, yellow calico, calico clear, clear moorish, dark moorish and red moorish). The coat color of the influences thermoregulation, adhesion of ectoparasites, and may be associated with productive and reproductive aspects. The coat is part of the breed qualification and there is still a predilection of breeders for certain colors. Due to the lack of knowledge about the inheritance mechanisms that explain coat variations in Gyr cattle, the objective was to perform a GWAS to identify candidate genes for the coat phenotype and perform fine mapping of the MC1R gene, a gene that has already been reported to affect the coat in other cattle breeds. A total of 574 Gir animals were genotyped with a commercial Zoetis low-density chip of 29,842 SNPs were used in nine genomic wide association (GWAS) scenarios using the single-step methodology. In addition, biological material was collected from 46 Gir cattle of all registerable coats and from 1 animal with the depigmented phenotype for PCR and analysis of the MC1R gene sequences for fine gene mapping. In the different scenarios of the GWAS analysis, regions were found present in BTA3, BTA6, BTA8, BTA9, BTA10, BTA16, BTA18, BTA21 and BTA26. After analysis of the regions obtained in the GWAS, candidate genes were listed in the different scenarios, proving to be a characteristic of polygenic order. A possible epistatic effect is also suggested in determining the coat of the Gir breed, as already observed in other bovine breeds. Furthermore, some polymorphisms and amino acid exchanges were observed in the MC1R gene, at positions c. 311 G>del, c.416 C>T (p.Ala139Val), c.460 A>C (p.Ser154Arg), c.583 T>C (p.Phe195Leu), c. 663 T>C (p.Ile221Ile) and c. 871 A>G (p.Ala291Thr), thus forming 7 haplotypes. There is a suggestion that some MC1R haplotypes cause depigmentation in Gyr cattle. In the present study, the genetic effects on coat color were evaluated and new candidate genes influencing the trait in the Gir breed were also proposed. Thus, making it possible to direct future studies that seek to decipher the genetic architecture of the trait and the development of genetic markers for selection.