Genetic polymorphism in Hsp90AA1 gene is associated with the thermotolerance in Chinese Holstein cows.

The heat shock protein 90 (Hsp90) is a copious and ubiquitous molecular chaperone which plays an essential role in many cellular biological processes. The objective of this study was to identify single nucleotide polymorphisms (SNPs) in the Hsp90AA1 gene and to determine their association with heat stress traits in Chinese Holstein cattle breed. Direct sequencing was used to identify new SNPs. Luciferase reporter assay methods were used to assess g.- 87G > C and g.4172A > G loci in the promoter activity and 3'-UTR, respectively. Quantitative real-time PCR was utilized to quantify the gene expression profile. Five SNPs were identified in 130 multiparous lactating cows: one SNP in the promoter, three SNPs in the coding region, and one in 3'-UTR were novel and reported for the first time in this study. As a result of promoter assay using dual luciferase assay system, the genotype CC showed the highest transcription activity region (13.67 ± 0.578) compared to the wild-type GG (3.24 ± 0.103). On the other hand, the result revealed that one of the selected microRNAs (dme-miR-2279-5p) was found to interact with the Hsp90AA1 3'-UTR sequence and to suppress the reporter activity markedly in the presence of the allele G (2.480 ± 0.136). The expression of Hsp90AA1 in cow bearing mutant allele C was higher (4.18 ± 0.928) than cows bearing wild-type allele G (1.008 ± 0.0.129) in stress season. In summary, there was an association between genetic variations in the Hsp90AA1 and thermoresistance. This association could be used as a marker in genetic selection for heat tolerance in Chinese Holstein cattle breeds.