Genetic effects of FTO gene insertion/deletion (InDel) on fat-tail measurements and growth traits in Tong sheep

Tong sheep is a kind of famous fat-tailed sheep in China, which no longer meets market demands because of the large amount of fat deposition in tail. Fat mass and obesity associated (FTO) gene regulates fatty acid transport and fat metabolism to affect obesity and is also reported to regulate phenotypic traits in healthy animals. To identify the insertion/deletion (InDel) variations of the FTO gene and evaluate their effects on fat-tail measurements and growth traits, 166 healthy individuals from Tong sheep were identified and analyzed. Herein, 10 novel InDel polymorphisms were founded in the Tong sheep FTO gene, which displayed intermediate polymorphism (0.25 < PIC < 0.5) and were in Hardy-Weinberg equilibrium (p > .05). Correlation analysis of 78 Tong sheep phenotypic traits data and InDel polymorphisms showed that eight InDel loci were significantly associated with partial growth traits (p < .05), four InDel loci were significantly correlated with fat-tail measurements (p < .05). In particular, individuals with genotype DD showed better phenotypic traits than individuals with other genotypes at male sheep InDel 5 and InDel 8 loci, which had small tail-fat dimensions while having good growth traits. These results confirmed potential usefulness of FTO gene in marker-assisted selection programs of Tong sheep breeding.