Differential Proportion of Ancestral MHC Haplotypes in Brangus Breed

GOSZCZYNSKI, D; POSIK, D; ROGBERG-MUÑOZ, A; MORALES, H; MUNILLA, S; GIOVAMBATTISTA, G; CORBI BOTTO, C; VILLEGAS-CASTAGNASSO EE; CANTET, RJC

Salt Lake City, Utah

Congreso; 35th Conference of the International Society for Animal Genetics.; 2016

International Society for Animal Genetics (ISAG).

Brangus breed was developed to use the superior characteristics of both founder breeds. The breed maintains the high adaptability to tropical and sub-tropical environments, disease resistance and hardiness from Zebu cattle, and the high reproductive capability, production and meat quality traits from Angus. It has been studied that the major histocompatibility complex (MHC), located on BTA23, encodes genes implicated in the adaptive immune response, and may be responsible for the adaptation to those environments. The objectives of this work were to study the MHC ancestral haplotypes in a Brangus sample to detect the breed of origin (Angus or Brahman) of each genotype, and then determine if there is a divergence from the overall genomic proportion. For this, a total of 169 animals (99 Brangus, 48 Angus and 22 Brahman) were genotyped using Affymetrix BOS1 (640K) Chip. Structure software v2.3.4 was used to estimate the whole genome fraction of each founding breed that remained in the sampled Brangus animals, with a subset of 5K SNPs evenly spaced over the 29 autosomes. The SNPs included in the MHC BTA23 region (5,585 SNPs within 7,013,913?28,998,760 bp) were primarily phased with ShapeIT2 algorithm, for further haplotype origin assessment with LAMP-LD package. Two other regions demonstrated for coat color (MC1R gene on BTA18: 1,682,065-2,046,164 bp) and polled trait (BTA1: 14,038,121-14,991,286 bp) were selected for Proof of Concept, as those traits were selected in Brangus for the Angus phenotype (solid coat color and polled). The result obtained for the whole genome composition of Brangus was 34.7% Brahman, ranging from 22.3% to 81.1%, while for the MHC region, the haplotypes appear to have originated from Brahman in 55.3 % of the chromosomes. As expected, the Proof of Control regions showed that the Angus haplotypes were nearly fixed, which supports that the divergence of the haplotypes of the MHC region may have originated in a selection process to promote adaptation to tropical and sub-tropical environments.