Determination of Genetic Effects of LIPK and LIPJ Genes on Milk Fatty Acids in Dairy Cattle.

In our previous genome-wide association study (GWAS) on milk fatty acids (FAs) in Chinese Holstein, we discovered 83 genome-wide significant single nucleotide polymorphisms (SNPs) associated with milk FAs. Two of them were close to lipase family member K () and lipase family member J (), respectively. Hence, this study is a follow-up to verify whether the and have significant genetic effects on milk FAs in dairy cattle. By re-sequencing the entire exons, and 3 kb of 5' and 3' flanking regions, two and seven SNPs were identified in and , respectively, including a novel SNP, ss158213049726. With the Haploview 4.1 software, we found that five of the SNPs in formed a haplotype block (D' = 0.96 ~ 1.00). Single-locus association analyses revealed that each SNP in and was significantly associated with at least one milk FA (p = < 1.00×10 ~ 4.88×10), and the haplotype-based association analyses showed significant genetic effects on nine milk FAs (p = < 1.00×10 ~ 3.98×10). Out of these SNPs, the missense mutation in gene, rs42774527, could change the protein secondary structure and function predicted by SOPMA, SIFT, and PROVEAN softwares. With the Genomatix software, we predicted that two SNPs, rs110322221 in and rs211373799 in , altered the transcription factors binding sites (TFBSs), indicating their potential regulation on promoter activity of the genes. Furthermore, we found that both and had relatively high expressions in the mammary gland. In conclusion, our research is the first to demonstrate that and genes have significant associations with milk FAs, and the identified SNPs might be served as genetic markers to optimize breeding programs for milk FAs in dairy cattle. This research deserves in-depth verification.