Remarkable genetic diversity detected at river buffalo Prolactin Receptor (PRLR) gene and association studies with milk fatty acid composition.

Prolactin is an anterior pituitary peptide hormone involved in many different endocrine activities and is essential for reproductive performance. This action is mediated by its receptor, the prolactin receptor, encoded by the PRLR gene. In this study, we sequenced and characterized the Mediterranean river buffalo PRLR gene (from the exon 3 to 10) and a remarkable genetic diversity was found. In particular, we found 24 intronic polymorphisms and 13 exonic SNPs, 7 of which were non-synonymous. Furthermore, the polymorphisms identified in the 3’UTR were investigated to establish their possible influence on microRNA binding sites. Considering all the amino acid changes and the observed allelic combinations, it is possible to deduce at least 6 different translations of the buffalo prolactin receptor and, consequently, the presence at the PRLR gene of at least 6 alleles. Furthermore, we identified a deletion of a CACTACC heptamer between the nucleotides 1102-1103 of exon 10 (3'UTR) and we developed an allele specific PCR to identify the carriers of this genetic marker. Finally, the SNP g.11188A>G, detected in exon 10 and responsible for the amino acid replacement p.His328Arg, was genotyped in 308 Italian Mediterranean river buffaloes and an association study with milk fat traits was carried out. The statistical analysis showed a tendency that approached the significance for the AA genotype with higher contents of odd branched-chain fatty acids (OBCFA). Thus, our results suggest that PRLR gene is a good candidate for gene association studies with qualitative traits related to buffalo milk production.