the Genetic variation of ACTN3 and MSTN genes in a cohort of endurance Arabian horses

Arabian horses are readily distinguishable in form and features, and they are widely known for endurance capability. This study is the first examining of endurance-related genes in Arabian horses born and raised in Syria. The major objective was to identify genetic variation in candidate genes that could potentially affect endurance traits and to associate them with endurance phenotypes. The two genes Alpha-actinin skeletal muscle isoform 3 (ACTN3) and Myostatin (MSTN) were sequenced. Performance traits were available for 42 recorded Arabian horses from Syria performed endurance racing over 40, 80, and 120 km distances. Based on the recorded mean speeds, horses were grouped according to their performance index into low and high performers. The comparative sequencing revealed a total of 13 variants in both studied genes, 12 variants in ACTN3 and one variant in MSTN. General linear model analyses showed that none of the analyzed variants has significant effect on any of the studied traits. However, for ACTN3, we found a 5’ UTR variant (12:26511704G>A) that predicted to cause a gain of an E4BP4 transcription factor binding site, and a variant in the 3´ UTR 12:26524930T>C that predicted to cause the abrogation of two predicted miRNA target sites (eca-miR-1296 and eca-miR-326) and thereby affect gene expression. For MSTN, a 5’ UTR variant 18:66495696A>G is predicted to cause the substitution of the transcription factor binding sites for HFH-1 and Sox-5 by binding sites for HFH-3 and E4BP4.