A genome-wide scan for tying-up syndrome in Japanese Thoroughbreds.

Tying-up syndrome, also known as recurrent exertional rhabdomyolysis in Thoroughbreds, is a common muscle disorder for racehorses. In this study, we performed a multipoint linkage analysis using LOKI based on the Bayesian Markov chain Monte Carlo method using 5 half-sib families (51 affected and 277 nonaffected horses in total), and a genome-wide association study (GWAS) using microsatellites (144 affected and 144 nonaffected horses) to map candidate regions for tying-up syndrome in Japanese Thoroughbreds. The linkage analysis identified one strong L-score (82.45) between the loci UCDEQ411 and COR058 (24.9-27.9 Mb) on ECA12. The GWAS identified two suggestive genomic regions on ECA12 (24.9-27.8 Mb) and ECA20 (29.3-33.5 Mb). Based on both results, the genomic region between UCDEQ411 and TKY499 (24.9-27.8 Mb) on ECA12 was the most significant and was considered as a candidate region for tying-up syndrome in Japanese Thoroughbreds.