| The mammary gland is an important functional organ on lactation, in which the gene expression level is dually controlled by genetic and environmental factors. The changes of expression level of important functional genes in mammary gland regulate growth, differentiation and milk synthesis, secretion and transportation. The mammary gland epithelial cell is the basic structural and functional unit on lactation. Research on lactation related genes’expression reveals how genes are activated, initiated, maintained for lactation and regulation of milk composition. Meanwhile, the regulation of dairy cow mammary gland lactation functional genes can significantly improve milk quality and milk production and have certain economic efficiency.In this study we used DGE of BGI corporation, which screened differentially expressed genes of high/low milk quality lactating dairy cow and dry milk dairy cow. FABP3gene was screened out, which had important effects on milk production traits by bioinformatics analysis, and verified by fluorescence quantitative RT-PCR. FABP3is a member of the fatty acid binding protein family and widely present in the myocardium, skeletal muscle and lactating breast in which fatty acids are highly in demand. It is involved in transient storage and transportation of intracellular fatty acids. Into the mitochondrial energy metabolism system, fatty acid is oxidized and decomposed to produce ATP and provides energy for organisms. It combines with fatty acids to form intracellular and extracellular concentration difference and promotes the cellular uptake of fatty acids.FABP3plays an important role in the milk fat synthesis signal transduction pathway. The present study focused on the interaction between FABP3and SREBP1, PPAR y. In this experiment, we used gene overexpression and RNA interference technology to regulate FABP3expression at the cellular level positively and negatively, aimed to increase and decrease its regulation on lactation level. We detected the changes in the expression and localization of SREBP1and PPAR y and the influence on the secretion of lipid droplets by using qRT-PCR, western blotting and laser confocal detection methods after changes of FABP3expression level. The results showed that, FABP3could regulate the expression of SREBP1(p<0.05) and PPARy (p<0.05) at mRNA and protein levels and increase secretion of lipid droplets (p<0.05).FABP3can combine with long chain fatty acids and has high affinity with palmitic acid, stearic acid and oleic acid. FABP3coordinates ACSL1and SLC27A6to let long chain fatty acids esterfication into TAG. In this experiment, we detected the effects of exogenous addition of palmitic acid, stearic acid and oleic acid and screened the optimal concentration and time, which had the most significant effects on FABP3expression. Dairy cow mammary gland epithelial cells were incubated with three kinds of fatty acids at optimal concentration and time and the changes of SREBP1and PPAR y protein expression level were detected by western blotting. The results showed, stearic acid increased PPAR y (P<0.01) and reduced SREBP1(P<0.05) expression, palmitic acid increased PPAR γ (P<0.01) and reduced SREBP1(P<0.05) expression, while oleic acid increased PPAR y (P<0.05) and SREBP1(P<0.01) expression. Confocal laser was used to detect the effect on the secretion of lipid droplets, and the results showed that three kinds of fatty acids significantly increased secretion of lipid droplets (P<0.05). |
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