Nucleotide Variants in TheTLR5 Gene and Promoter Methylation with A Susceptibility to Brucellosis in Chinese Goats

In this study, we aimed to identify genetic variants of the TLR5 gene and the promoter methylation level with a susceptibility to brucellosis in Chinese Saanen dairy goats (SN). We randomly collected 205 genetically unrelated animals from five Chinese goat breeds, including the Saanen dairy goat (SN, n = 67), Tibetan goat (TG, n = 35), Chuannan black goat (CN, n = 30), Meigu goat (MG, n = 37) and the Jianzhou big-ear goat (JZ, n = 36). A blood sample was collected from each individual and used for the detection of brucellosis, TLR5 polymorphism identification and the detection of promoter methylation. In total, twenty-four SNPs were identified in the five investigated breeds. The allele and genotype frequency of the four loci (g.435C>T, g.690G>T, g.978A>G and g.1832A>G) were correlated with a seroprevalence of brucellosis in the SN goats. An r2 linkage disequilibrium (LD) was detected in SN, CN, TG and MG, but not in the JZ goats. Ten methylation sites were detected on the first CpG island with DNA methylation levels ranging from 0.2% to 5.2%, and twenty-two methylation sites were found on the second methylation island with a 2.3% to 12.1% methylation. The methylation levels of the two CpG islands in the healthy SN were significantly higher than those recorded in the brucella -infected SN (p <0.05). Our findings demonstrated that genetic variations and the promoter methylation of TLR5 were associated with a brucellosis risk in SN goats. These results will be helpful for further studies of disease resistance in ruminants.