Association of Aberrant DNA Methylation Level in the CD4 and JAK-STAT-Pathway-Related Genes with Mastitis Indicator Traits in Chinese Holstein Dairy Cattle

Abstract

The present study was designed to evaluate the gene expression and DNA methylation level in the promoter region of the <i>CD4</i> and the JAK-STAT-pathway-related genes. A total of 24 samples were deployed in the gene expression and 118 samples were used in the DNA methylation study. Student's <i>t</i>-tests were used to analyze the gene expression and DNA methylation. The evaluation of DNA methylation in promoter regions of <i>JAK2</i> and <i>STAT</i><i>5A</i> revealed hypo-methylation levels of CpG sites and higher gene expression in cows diagnosed with mastitis as compared to the healthy control, and vice versa in those with <i>CD4</i>. DNA methylation was negatively correlated with gene expression in <i>JAK2</i>, <i>STAT</i><i>5A</i>, and <i>CD4</i> genes. Six, two, and four active transcription factors were identified on the CpG sites in the promoter regions of <i>JAK2</i>, <i>STAT</i><i>5A</i>, and <i>CD4</i> genes, respectively. Regarding correlation analysis, the DNA methylation levels of <i>CD4</i> showed significantly higher positive correlations with somatic cell counts (<i>p</i> < 0.05). Findings of the current study inferred that aberrant DNA methylation in the CpG sites at the 1 kb promoter region in <i>JAK2</i>, <i>STAT</i><i>5A</i>, and <i>CD4</i> genes due to mastitis in cows can be used as potential epigenetic markers to estimate bovine mastitis susceptibility in dairy cattle.