Study On Relationship Between Polymorphism And Expression Of LOC-1 Gene And Milk Production Traits In China Holstein

In this study, we explored the influence of sampling factors on determination of milk composition factors and the influence of seasons, parity and lactation period on China Holstein cows milk production traits, and measured the biochemical indicators, such as Holstein cows fasting blood-glucose and triglyceride (TG), total cholesterol (TC), high density lipoprotein (HDL) and low density lipoprotein (LDL) and analyzed the correlation between them and milk composition. Meanwhile, we exploited DNA pooling to screen single sucleotide polymorphisms (SNP) mutation site of LOX-1, and analyzed the correlation between SNP and milk production traits through high resolution dissolution curve (HRM) combined with sequencing. In addition, we inverstigated whether methylation regulated the expression of LOX-1 on the gene promoter regions. Finally, by total RNA was extracted from somatic cells in milk, the full-length sequence coding area of LOX-1 gene was cloned and the LOX-1, beta actin were detected to compare the expression in different individuals, providing guidance for breeding cows. The main results were as follows:1. There were significant differences between sample methods and milk composition (P<0.01), between seasons, parity, lactation period and milk production, milk protein rate, butterfat rate, Lactose content value (P< 0.01). Average milk production in dairy cows had a significantly negative correlation with milk fat percentage and protein percentage, and moderate correlation with the milk fat content and protein content..These results showed that LDL levels of blood composition had a significant effect on cows butterfat rate.2. There were low polymorphism (PIC were respective 0.200,0.200,) of introns 4 double base mutations on 10839/10840 (TG/CA), moderate polymorphism (PIC> 0.25) of the rest of the polymorphic loci, no highly polymorphic loci and no Hardy-Weinberg equilibrium (P< 0.05) every mutation loci. Mutation loci in exon 3:4927 T to G made encoding amino acids phenylalanine become valine,5132 C to T made encoding amino acids threonine become isoleucine.8 polymorphic mutation loci in 5 ’non-coding region and exon 3 significantly influenced the milk production traits in cows. The methylation was not detected at 5’UTR, therefore, it needs further study on whether its effect on milk production traits was associated with methylation regulation.3. Total RNA was extracted from somatic cells in milk, and the expression of LOX-1 gene was detected by PCR. The results showed that the content of somatic cells in milk was rich, and vitality could fulfill the requirement of RNA extraction. Integral and pure RNA extracted from somatic cells could be used to synthesize cDNA, meanwhile, LOX-1 gene encoding area, beta-actin were correctly amplified. There were significant expression differences among different milk production, butterfat content, indicating that LOX-1 gene probably participated in the fat metabolism regulation in cows.