​Genetic Polymorphism within Exon 3 of HSP90AA1 Gene and its Association Studies in Sahiwal and Crossbred Cows

Abstract

Background: Heat shock proteins (HSPs) are molecular chaperones that play a critical role in recovering cells from stress and form a primary system for intra cellular self defense. They are highly conserved and play a crucial role in cellular thermo tolerance and heat stress response. Though there are many HSP genes, thermo tolerance is mainly correlated with HSP70 and HSP90 genes in Livestock species. Polymorphisms in these genes have shown an association with heat tolerance, milk production, fertility and disease susceptibility in livestock. They can be used as genetic markers for the selection of animals with better climate resilience, immune response and superior performance. Methods: The present study was carried out in Sahiwal (n=50) and Crossbred cows (n=50) with the objective to identify polymorphisms in HSP90AA1 gene. A 450 bp fragment of bovine HSP90AA1 gene covering exon3 was subjected to Polymerase Chain Reaction-Single-Strand Conformation Polymorphism (PCR-SSCP) technique to identify the polymorphism. PCR-SSCP patterns were correlated with the physiological, productive and reproductive traits in Sahiwal and crossbred cows using the univariate GLM model of SPSS 25. Result: The PCR-SSCP of exon 3 of HSP90AA1 gene yielded two conformational patterns AA and AB corresponding to two allelic variants A and B in both Sahiwal and crossbred cows. The allele frequencies of A and B were 0.78 and 0.22 and 0.84 and 0.16 in Sahiwal and crossbred cows, respectively. The association analysis of SSCP patterns revealed that genotype AA had higher lactation length in Sahiwal cows and higher total lactation milk yield and peak yield in crossbred cows.