Diplotype-based assessment of GNRHR gene polymorphisms and their role in determining litter size at birth in the Malabari goat population of South India

Abstract

The Gonadotropin Releasing Hormone Receptor (GNRHR) gene, a key regulator of the hypothalamo-pituitary-gonadal axis, plays a pivotal role in modulating reproductive potential in mammals by influencing the release of gonadotropins. In this study, we conducted a comprehensive population genetic analysis of haplotypes and diplotypes of the GNRHR and explored their association with litter size at birth in the prolific Malabari goat breed of South India. Utilizing PCR-single strand conformation polymorphism (SSCP) and PCR-sequencing-based typing (SBT) techniques, we genotyped 185 Malabari goats for diplotypes encompassing specific single nucleotide polymorphisms (SNPs) at c.–33A>G, c.–29 T>G, c.48 G>A, c.75 G>A, and c.209 T>G loci of the GNRHR gene. The PCR-SSCP and PCR-SBT revealed the presence of seven diplotypes and six haplotypes within the study population. Our results, as determined by ordinal logistic regression analysis, demonstrated a highly significant (p<0.01) influence of GNRHR diplotypes on litter size at birth up to the third parity, with a significant (p<0.05) effect observed in the fourth parity in Malabari goats. Specifically, the odds of multiple births were found to be 53.3% and 80.7% higher for AGAGG/ATGGT diplotypes compared to AGAGG/AGAGG diplotypes in the first and second parity, respectively. Furthermore, the odds ratio analysis highlighted a higher percentage of multiple births in AGAGG/AGAAG diplotypes during the third and fourth parities compared to other diplotypes in Malabari goats. Collectively, our findings suggest that heterozygote diplotypes confer a reproductive advantage over homozygous diplotypes for litter size at birth in the Malabari goat breed.