Genetic Structure of Angus and Salers in Relation to SNP Associated with Pulmonary Arterial Pressure

Cattle living in the Rocky Mountains (elevations > 1,500 m) are often at risk of contracting high altitude disease. Low atmospheric pressure at high altitudes causes pulmonary hypertension and potentially right heart failure. Pulmonary arterial pressure (PAP) is an indicator for pulmonary hypertension. PAP measurements of < 41 mmHg are categorized as low risk for the development of pulmonary hypertension at high altitudes. Genetic resilience to the disease is possible and can be achieved through breed or within breed selection. Here we explored differences between Angus raised at 2,150 m divided into low (< 41 mmHg; n = 24) and high PAP (> 41 mmHg; n = 41) groups and Salers (n = 24) at loci associated with PAP. The Salers sampled, a French mountainous breed (< 4,800 m elevation), were all full blood. The mean Angus PAP score was 49 ± 2.1 mmHg (range 35 to 115). To determine the population structure between the two breeds, 121,756 SNP pruned from the 777,972 SNP on BovineHD beadchip were evaluated using Admixture to infer ancestral populations. Previously identified SNP (n = 40) associated with PAP in Angus cattle through genome-wide association studies were used to assess genetic diversity of both breeds. Chi-square tests were performed to identify statistical differences among the allele frequencies and breed groups. We used TreeSelect to identify allele frequency divergence from a central node due to selection. Admixture revealed by the lowest-cross validation error that two distinct populations existed. Chi-square tests of SNP genotypic frequencies among the groups revealed that 23 of the 40 SNP differed (P < 0.025). Sixteen SNP differed between both low and high PAP Angus groups versus Salers. Also these results show the high PAP Angus genotypic frequencies differentiated themselves from the low PAP Angus genotypic frequencies. However, both high and low PAP Angus group allele frequencies showed evidence of approaching the frequencies observed in Salers. TreeSelect identified four SNP under selection. Of those SNP, three allele frequencies were similar between low PAP Angus and Salers, suggesting natural or artificial selection for both populations. These results indicate genetic diversity exists between Angus and Salers cattle which can be used to increase resilience to high altitude disease. Therefore, cattle breeders may choose to address such a problem through breed choice, selection within a breed, or both.