247 ASSOCIATIONS BETWEEN HEAT SHOCK PROTEIN 70 GENETIC POLYMORPHISMS AND CALVING RATES OF BRAHMAN-INFLUENCED COWS

Abstract

Stress proteins and their genetic polymorphisms have been associated with decreased male and female fertility. Our objectives were to 1) identify single nucleotide polymorphisms (SNP) located in the promoter region of the bovine heat shock protein 70 (Hsp70) gene and 2) evaluate associations between Hsp70 SNP and calving rates of multiparous Brahman-influenced cows (n = 99). Genomic DNA was extracted from the buffy coats of EDTA- treated whole blood. Primers HSP-Pro749F (GCCAGGAAACCAGAGACAGA) and HSP-Pro1268R (CCTACGCAGGAGTAGGTGGT) were used for PCR amplification of a 539-base segment of the bovine Hsp70 promoter (GenBank accession number M98823). Eleven single nucleotide polymorphisms were detected: 8 transitions (G1013A, n = 2; G1045A, n = 8; C1069T, n = 4; A1096G, n = 14; G1117A, n = 12; T1134C, n = 7; C1154G, n = 11; andT1204C, n = 56), 2 transversions (A1125C, n = 53; and G1128T, n = 51), and 1 deletion at base position 895 (n = 37). Within an SNP, calving percentages were compared by chi-square analysis. Concentrations of Hsp70 and Julian date were analyzed by ANOVA, with each SNP represented as the main effect in the model. Cows that were homozygous for the minor allele at both transversion (A1125C and G1128T) sites had lower (P < 0.05) calving rates when compared with cows that were homozygous for the primary allele (48 v. 75%). Homozygous and heterozygous deletion of cytosine at base 895 resulted in lower (P < 0.05) calving percentages than homozygous cytosine cows (8, 50, 82%; respectively). In addition, DD cows had the latest (P < 0.05) Julian calving date. Eighteen Hsp70 promoter haplotypes were deduced, and 7 of those haplotypes (n = 37) included the deletion at base 895. Thirty-two cows had the haplotype consistent with the sequence deposited at GenBank, and the remaining 30 cows had an SNP other than the deletion. Cows with the deletion haplotypes had greater (P < 0.05) serum Hsp70 concentrations and lower (P < 0.05) calving rates (5.1, 4.7, and 3.5 MSE 0.5 ng mL^-1; and 35, 78, and 87%; respectively, for Deletion, No, and Yes). Furthermore, cows with the deletion haplotypes had the latest (P < 0.05) Julian calving date (85, 77, and 73 d, respectively, for Deletion, No, and Yes). Our results suggest that the promoter region of the bovine Hsp70 gene is polymorphic and might be useful in selecting cows with greater fertility.