Evidence of positive selection towards Zebuine haplotypes in the BoLA region of Brangus cattle.

The Brangus breed was developed to combine the superior characteristics of both of its founder breeds, Angus and Brahman. It combines the high adaptability to tropical and subtropical environments, disease resistance, and overall hardiness of Zebu cattle with the reproductive potential and carcass quality of Angus. It is known that the major histocompatibility complex (MHC, also known as bovine leucocyte antigen: BoLA), located on chromosome 23, encodes several genes involved in the adaptive immune response and may be responsible for adaptation to harsh environments. The objective of this work was to evaluate whether the local breed ancestry percentages in the BoLA locus of a Brangus population diverged from the estimated genome-wide proportions and to identify signatures of positive selection in this genomic region. For this, 167 animals (100 Brangus, 45 Angus and 22 Brahman) were genotyped using a high-density single nucleotide polymorphism array. The local ancestry analysis showed that more than half of the haplotypes (55.0%) shared a Brahman origin. This value was significantly different from the global genome-wide proportion estimated by cluster analysis (34.7% Brahman), and the proportion expected by pedigree (37.5% Brahman). The analysis of selection signatures by genetic differentiation (F st ) and extended haplotype homozygosity-based methods (iHS and Rsb) revealed 10 and seven candidate regions, respectively. The analysis of the genes located within these candidate regions showed mainly genes involved in immune response-related pathway, while other genes and pathways were also observed (cell surface signalling pathways, membrane proteins and ion-binding proteins). Our results suggest that the BoLA region of Brangus cattle may have been enriched with Brahman haplotypes as a consequence of selection processes to promote adaptation to subtropical environments.

Nonsynonymous changes of equine lentivirus receptor-1 (ELR1) gene in amino acids involved in the interaction with equine infectious anemia virus (EIAV).

Equine lentivirus receptor-1 (ELR1) has been characterized as the specific functional receptor that mediates equine infectious anemia virus (EIAV) entrance to horse macrophages. This receptor is tumor necrosis factor receptor superfamily member 14 (TNFRSF14). The aim of this study was to investigate the occurrence of allelic variants in the coding sequence of equine TNFRSF14 gene by screening for single-nucleotide polymorphisms (SNPs) in different equine populations. Forty seven horse samples were randomly selected from a reservoir of EIAV-seropositive and seronegative samples collected from different outbreaks and regions of Argentina. DNA samples were scanned via PCR and direct sequencing of exon 3 and exon 5 of TNFRSF14 gene. A total of 21 SNPs were identified, of which 11 were located in coding sequences. Within exon 5, four SNPs caused nonsynonymous substitutions, while two other SNPs caused synonymous substitutions in crucial residues (Ser112 and Thr114) implicated in the interaction with EIAV. Despite some of exon 5 variants occurred exclusively in EIAV-positive or EIAV-negative horses, critical residues for the function of the mature protein were conserved, accounting for selective pressures in favor of preserving the specific function of TNFRSF members and the host immune response. To our knowledge, this is the first report of the existence of allelic variations involving some crucial amino acid residues in horse ELR1. Further, it could be an initial step to test the possible functional relevance and relationship of these variants with EIAV infection and disease progression as well as to develop preventive strategies.