The sarcomeric α-actinins, encoded by the genes ACTN2 and ACTN3, are major structural components of the Z-line and have high sequence similarity. α-Actinin-2 is present in all skeletal muscle fibres, while α-actinin-3 has developed specialized expression in only type 2 (fast, glycolytic) fibres. A common single nucleotide polymorphism (SNP) in the human ACTN3 gene (R577X) has been found to influence muscle performance in elite athletes and the normal population. For this reason, equine ACTN3 (eACTN3) is considered to be a possible candidate that may influence horse performance. In this study, the intron/exon boundaries and entire coding region of eACTN3 has been sequenced in five Australian horse breeds (Thoroughbred, Arabian, Standardbred, Clydesdale and Shire) and compared to the eACTN3 GenBank sequence. A total of 34 SNPs were identified, of which 26 were intronic and eight exonic. All exonic SNPs were synonymous; however, five intronic SNPs showed significant differences between breeds. A total of 72 horses were genotyped for a SNP located in the promoter region of the eACTN3 gene (g. 1104 A>G) which differed significantly between breed groups. We hypothesize that this polymorphism influences eACTN3 expression and with further studies may provide a novel marker of horse performance in the future.
The study is from the Institute for Neuroscience and Muscle Research, Children’s Hospital at Westmead, the Faculty of Veterinary Science, and the Faculty of Medicine, University of Sydney, Sydney, NSW; and the Murdoch Childrens Research Institute, The Royal Children’s Hospital, Melbourne, VIC, Australia.
Thomas KC, Hamilton NA, North KN, Houweling PJ. Gene 2014 Jan 15 [Epub ahead of print].