| Angiopoietin-like protein 5(ANGPTL5)is a subtype of the ANGPTLs family,which is mainly expressed in the heart and adipose tissue.Studies had showed the roles of ANGPTL5 in angiogenesis and regulating lipid synthesis and metabolism.In present study,the polymorphisms of the ANGPTL5 gene were detected in the Chinese Simmental and Chinese Holstein cattle.The correlations between SNPs and economic traits of cows and beef cattle were analyzed.The expression levels in bovine adipose tissue,muscle tissue and various organs as well as pre-adipocytes were detected by real-time fluorescent quantitative PCR amplification.On the other hand,the overexpression and RNAi vectors of ANGPTL5 were constructed and transfected into bovine preadipocytes and mammary epithelial cells.The intracellular triglyceride contents in different groups were detected to verify the effect of ANGPTL5 on cell fat metabolism.The results showed that there are three SNPs,I1-1776 G>A,I5-2743 A>C and I5-2757 T>C detected in ANGPTL5 of Chinese Holstein cows.Among them,I5-2743 A>C and I5-2757 T>C had no correlations with milk quaility traits.I1-1776 G>A site was significantly correlated with urea nitrogen content(p<0.05).In the Chinese Simmental population,four SNPs were detected,I1-1776 G>A,I2-77 T>C,I2-1505 A>T and I2-1391 C>T.Among them,the I1-1776 G>A of ANGPTL5 was significantly correlated with the weight of front hoof,back hoof,liver,spleen and back fat(p<0.05).I2-1391 C>T site was significantly associated with fore hoof weight,hind hoof weight,liver weight,spleen weight and back fat thickness(p<0.05).I2-1391 C>T and I2-1505 A>T were significantly correlated with back fat thickness(p<0.05).The ANGPTL5 gene has the highest expression level in the heart and the lowest expression level in the liver.The expression level of ANGPTL5 in pre-adipocytes was significantly lower than that in mammary epithelial cells,and the expression levels of genes in subcutaneous fat and visceral fat were significantly higher than those in pre-adipocytes.Moreover,the overexpression of bovine ANGPTL5 gene significantly increased triglyceride content in both bovine preadipocytes and mammary epithelial cells(p<0.05),while the interference of ANGPTL5 gene significantly reduced the content of triglyceride in preadipocytes(p<0.05),the interference of ANGPTL5 gene significantly increased the content of triglyceride in mammary epithelial cells(p<0.05).Taken together,the results of this study suggest that SNPs in the intron region of ANGPTL5 gene had a significant correlation with meat and milk quality traits;ANGPTL5 gene expression promotes intracellular triglyceride synthesis.The above results provide a basis for the analysis of the function of ANGPTL5 on fat metabolism,and provide functional genes and genetic markers for milk quality and meat quality traits improvement as well as molecular breeding. |
