Regulation Of Bovine SCD3 On Lipid Metabolism And Its Promoter Region SNPs Analysis In Chinese Simentals

Cattle husbandry is a significant part of our country’s modern agricultural production system.Optimizing outstanding beef cattle breeds at the early stage of breeding,and selecting beef cattle breeds with strong intramuscular fat deposition ability and good meat production performance play a vital role in improving beef quality.Obtaining new functional genes with clear functions,molecular mechanisms,and independent intellectual property rights has great significance and application value for the improvement of beef cattle breeds in our country.Syndecan-3(SDC3)gene,as a new type of feeding behavior and weight regulator,is a regulatory factor in SDCs and plays a vital role in regulating energy balance.This gene could express in the hypothalamic region,control energy balance and participate in the regulation of feeding behavior.Meanwhile,SDC3 also involved in regulating the activity of the melanocortin system,effectively regulating energy intake,expenditure and peripheral glucose metabolism.Based on its crucial role in energy metabolism,we speculated that SDC3 may have a significant regulatory effect on cattle lipid metabolism.This experiment verified the effects of SDC3 gene on lipid metabolism at the level of cell,living body,and population.At the cellular level,the overexpression vector p BI-CMV3-SDC3 and si RNA were constructed so as to change the expression level of SDC3,lipid metabolism related genes and the content of the triglycerides,cholesterol,fatty acids,lipid droplets in bovine fetal fibroblasts and adipocytes.The result revealed that the SDC3 gene positively regulates the levels of triglycerides,cholesterol and the formation of lipid droplets,also can change the content of fatty acids.We recorded the growth curve of SDC3-knockout mice,observed the histological morphology and detected the serological index,then found that SDC3-knockout mice can significantly reduce the weight of male mice,the size of fat cells,and the content of triglyceride and cholesterol in adipose tissue,it also reduced the content of triglyceride,cholesterol and glucose in the blood,and increased the content of highdensity lipoprotein.At the bovine population level,we applied the relevant traits data of 135 Simmental,then 10 single nucleotide polymorphisms(SNPs)were identified in the promoter region of SDC3 gene.Among them,both g.123236647C>G and g.123236666C>G have a significant correlation with the marbling grade of Chinese Simmental beef(p<0.05).The site of g.123236666C>G has a great correlation with the fat coverage and fat color of Chinese Simmental beef(p<0.05).After linkage and haplotype analysis,among the genotypes formed,H2H2 was strongly related to the marble pattern and fat color of Chinese Simmental(p<0.05).H2H4 and H2H5 was significantly correlated with fat coverage and flesh color,respectively(p<0.05).These results can be used as molecular markers for marker assisted-selection(MAS)in beef cattle breeding programs.Through the detection of multiple levels and indicators of the SDC3 gene,our study explored the relationship between the candidate gene and lipid metabolism from the perspective molecular genetics,revealed the regulatory effect of SDC3 on lipid metabolism at the cellular and in vivo level.Ultimately,obtained the relevant molecular markers would apply to molecular breeding and early breeding of cattle.