The Regulation Of Genome-wide DNA Methylation And Key Genes Analysis Of Xinjiang Brown Cattle Mastitis Resistance

Xinjiang Brown cattle were selected as the research object in this study.Population genetic analysis was used to select Xinjiang Brown cattle with different SCC levels.Whole genome methylation patterns of different somatic cell numbers of Xinjiang brown cattle were constructed by using the MeDIP-seq method,and the DNA methylation degree of TRAPPC9 gene was analyzed by BSP method;resolve the genetic variation mechanism of genes closely related to mastitis resistance from population and epigenetic levels.The main results are as follows:(1)The 5 739 DHI evaluation records of Xinjiang Brown Cattle Breeding Center from 2014 to 2017 were collected.The effect of factors such as year,season,parity,and breed on somatic cell scores was analyzed using the least-squares analysis of SAS 9.1 software.The results showed that the annual,seasonal,parity,and cultivar had a significant effect on somatic cell scores(P<0.01).The somatic cell score of Xinjiang Brown cattle was significantly lower than that of Chinese Holstein cattle.The genetic parameters on the milk production traits of Xinjiang brown cattle were estimated by DMU software.The results showed that the heritability somatic cell of Xinjiang brown cattle was 0.13.(2)DNA methylation co-immunoprecipitation sequencing technology was used to detect genome-wide DNA methylation on blood samples of different somatic cell numbers in Xinjiang Brown cattle.Data analysis revealed that the two groups had 49 757 183,37 459 756 reads compared to the unique position of the reference genome.The peaks in the intergenic region are the most,followed by introns,exons,and promoters.There were 1934 unique differential genes corresponding to different regions of DNA methylation.(3)The enrichment of CpG island in the differential DMR region of TRAPPC9 and CD4 genes were analyzed by combining differential DMR in previous MeDIP-seq.With reference to the methylation level of healthy cattle,using BSP analysis,it can be seen that the CpG methylation status of the DMR region ofTRAPPC9 gene in the clinical mastitis cattle was higher.In the DMR region of CD4 gene,the methylation rate of CpG islands in clinical mastitis cattle was significantly lower than that in healthy cattle.