Molecular characterization and polymorphism studies of exon 10 of the Follicle stimulating hormone receptor (FSHR) gene in Indian cattle breeds

Abstract

FSH receptors are important binding sites of the follicle stimulating hormone (FSH) in ovaries and are coded by the FSHR gene which has 10 exons and 9 introns. Exon 10 is the largest (>1200 bp) of all the exons. In the present study, exon 10 of the FSHR gene partial coding sequence (CDS) was cloned and characterized in Sahiwal and Hariana cattle breeds, and DNA polymorphism was investigated using AluI/PCR-RFLP assay. The partial CDS of the Sahiwal and Hariana FSHR exon 10 was 99.3% to 100% similar to exotic cattle breeds at the nucleotide and amino acid level. A missense mutation was found in Sahiwal and Hariana at position 1118 (C→G) that caused an amino acid change at 373 (Thr→Ser) and two nonsense mutations were found at position 729 (G→A), 1180 (C→T). Phylogenetic analysis clearly showed that Sahiwal and Hariana cattle are more closely related to yak and Bos taurus. The 306 bp region of exon 10 on digestion with AluI restriction enzyme revealed three types of genotypes, namely: CC (243 bp and 63 bp), GG (193 bp, 63 bp and 50 bp) and CG (243 bp, 193 bp, 63 bp and 50 bp), where the CG genotype was more frequent (45.0%) than CC (13.5%) and GG (41.5%) genotypes, and the frequency of the G allele was higher (0.64) than the C allele (0.36) in all the screened animals. Chi square (χ2) analysis revealed that the screened animal population was in Hardy-Weinberg equilibrium. An association study revealed a significant (P<0.05) difference between Total milk yield and Lactation period where the CC genotype showed a higher milk yield than other genotypes.