Analysis Of Association Between OLR₁ Gene Mutation And Milk Production In Chinese Holstein Cattle

OLR₁ gene regulates the mechanism related to the internalization of certain proteins in mammary epithelial cells and the immune response,and is mainly expressed in the mammary tissue of dairy cows.In order to explore the correlation between OLR₁gene and milk production performance of dairy cows,this study took Chinese Holstein cattle from a large-scale dairy farm in Ningxia as the research object,collected the milk production performance data,and detected the genetic polymorphism of OLR₁ gene by direct DNA sequencing and PCR-SSCP typing.The correlation between OLR₁ gene mutation sites and milk production traits was investigated by using single factor analysis of variance in SPSS25.0 general linear model and Duncan’s multiple comparison method,so as to find out the candidate genes and their functional variation sites that really affect milk production traits of Chinese Holstein cattle in Ningxia,and provide reference for molecular marker-assisted selection of Chinese Holstein cattle.The main research results are as follows:1.The CDS coding region of OLR₁ gene of Chinese Holstein cattle was 822 bp,encoding 273 amino acids.The theoretical isoelectric point of the amino acid encoded by OLR₁ gene was 6.66,the instability index was 43.05,and the total average hydrophilicity was-0.399,indicating that OLR₁ protein was an unstable protein with weak hydrophilicity.It had a transmembrane structure and was located in the plasma membrane.The secondary and tertiary structures were mainlyα-helix and random coil.It is a non-secreted protein and has no signal peptide.2.A total of 11 mutation sites were identified in the OLR₁ gene of Chinese Holstein cattle,which were the g.386 A>G transition in the 5’UTR-Exon1 region,respectively,and produced two genotypes of AA and AB,which belonged to low polymorphism（PIC<0.25）;Exon5-Intron5 region g.9982 G>T transversion,g.10015G>A transition,g.10035 G>A transition,g.10063 T>C transition,g.10092 G>C transversion,g.10108G>A transition,g.10166 G>C transversion和g.10227 G>A transition resulted in AA,AB,AC and BB genotypes,which were highly polymorphic（PIC>0.5）;The transversion of g.10858 T>G and g.10886 C>A in Exon6-3’UTR region resulted in AA,AB and AC genotypes,which were moderately polymorphic（0.25<PIC<0.5）.3.The results of association analysis between OLR₁ gene mutation site and milk production traits of Chinese Holstein cattle and the results of allelic deletion analysis showed that the OLR₁ gene mutation site was significantly associated with some milk production traits of Chinese Holstein cattle.In conclusion,the correlation analysis between OLR₁ gene mutation sites and milk production performance of Chinese Holstein cattle indicated that OLR₁ gene could be used as a candidate gene affecting milk production traits,providing reference basis for the subsequent genetic improvement of Chinese Holstein cattle population.