Genetic Polymorphism Of GPAM Gene And Its Association Analysis With Milk Fat Traits And Functional Identification In Cows

Glycerol-3-phosphate acyltransferase,mitochondrial(GPAM)is a key enzyme in the first step in the synthesis of triglyceride,which has a great influence on the formation process of milk fat.This experiment is to study the effect of GPAM gene on milk fat level in Chinese Holstein cows.In this study,firstly,we detected the genetic polymorphisms of GPAM by using PCR-RFLP method to analyze the associations of GPAM single nucleotide polymorphisms(SNPs)with milk production traits in Chinese Holstein cows.The results show that,in Chinese Holstein cows,three SNPs were detected:E20-3386G>A,I18-652A>G and I18-726A>G.The polymorphism site E20-3386G>A is significantly associated with lactoprotein rate and somatic cell count(p<0.05);the polymorphism site I18-652A>G is significantly associated with lactoprotein rate and dry matter content and somatic cell count(p<0.05);the polymorphism site I18-726A>G is significantly associated with lactoprotein rate,milk yield,dry matter content,urea nitrogen content and somatic cell count(p<0.05).In the following experiment,in order to study the relationship of GPAM and lipid metabolism,we constructed a bovine GPAM overexpression vector and a RNA interference vector,then transfected bovine mammary epithelial cells respectively.The results indicate that in bovine mammary epithelial cells,GPAM could regulate the expression levels of AGPAT4 m RNA and protein,which is also essential in the lipid metabolism pathway.Under the circumstance of overexpression of GPAM,the expression level of AGPAT4 was also increasing significantly;vice versa.At the same time,bovine GPAM expression increased triglyceride content and knockdown of GPAM expression significantly reduced triglyceride content(p<0.05).The overall results indicate GPAM might play an important role in lipid metabolism.