Abstract
BACKGROUND: Heat stress (HS) poses a significant challenge to the dairy industry, affecting both the health and productivity of dairy cows. Identifying candidate genes and single nucleotide polymorphisms (SNPs) associated with HS is critical to improving heat tolerance of dairy cows. In our previous work, the eukaryotic translation initiation factor 4E (EIF4E), heat shock protein family A member 4 (HSPA4), and inositol 1,4,5-trisphosphate receptor type 2 (ITPR2) genes were found to play critical roles in the HS response of dairy cows. RESULTS: In this study, we further validated the gene expression patterns and genetic effects of the three candidate genes on HS response and milk production in Chinese Holstein cows. A total of 21 SNPs were identified by sequencing the exon and 2000 bp flanking region of the EIF4E (4 SNPs), HSPA4 (8 SNPs), and ITPR2 (9 SNPs) in pooled DNA samples from 70 Holstein bulls. Among these, two SNPs (g.44653172A > G and g.44660065C > T) were located in the coding exon and the 3' untranslated region of the HSPA4 gene, respectively. Association analyses were conducted between identified SNPs and three HS traits and six milk production traits in a population of 1,160 Chinese Holstein cows. The SNP-based association analysis identified significant associations between ten SNPs and HS traits (P < 0.05), as well as eight SNPs and milk production traits (P < 0.05). In the HSPA4 gene, five SNPs (g.44618036G > A, g.44624256 A > C, g.44624428T > C, g.44653172 A > G, and g.44660065 C > T) were significantly associated with rectal temperature (RT; P < 0.05). Notably, no SNPs were associated with milk production traits. Haplotype blocks containing g.44,653,172 A > G and g.44,660,065 C > T also showed significant associations with RT (P < 0.05). Further analysis suggests that g.44,660,065 C > T affects the stability of the mRNA secondary structure, microRNA and transcription factor binding, thereby potentially influencing the gene expression of HSPA4. CONCLUSION: In conclusion, we demonstrated that these three genes had significant genetic effects on HS and milk production traits. And g.44,660,065 C > T in the HSPA4 gene could be used as functional molecular markers for the genetic selection of dairy cows for improving heat tolerance without compromising their high milk performance.