Polymorphism of exon 10 of prolactin receptor gene and its rela-tionship with prolificacy of Jining Grey goats

Abstract

Prolactin receptor (PRLR) gene was studied as a candidate gene for the prolificacy of Jining Grey goats. Five pairs of primers were designed to detect single nucleotide polymorphisms of exon 10 and part of 3'untranslated region (UTR) of PRLR gene in both high fecundity breed (Jining Grey goat) and low fecundity breeds (Liaoning Cashmere goat, Boer goat and Angora goat) by PCR-SSCP. The nucleotide sequence of exon 10 and part of 3'UTR of caprine PRLR gene was spliced in this study for the first time. The length of this sequence was 1,118 bp. This sequence shared 98.33%, 93.92%, 74.52% homology with the published mRNA of PRLR gene of sheep, cow and human separately, and shared 78.29% homology with the published partial genomic sequence of PRLR gene of the alpaca. Only the products amplified by primers P1, P2, P4 displayed polymorphisms. For primer P1, two genotypes (AA and AB) were detected in both Jining Grey goats and Liaoning Cashmere goats, two genotypes (AA and AC) were detected in Angora goats, and only genotype AA was detected in Boer goats. Sequencing revealed two mutations (186G-->A and 220T-->C) of PRLR gene in the genotype AB in comparison to the genotype AA. The former mutation resulted in an amino acid change of Asp-->Asn, and the latter mutation resulted in an amino acid change of Leu-->Pro. Only one mutation (140A-->G) was found in the genotype AC in comparison to the genotype AA, and this mutation did not cause any amino acid change. The difference of the least squares means (LSM) for litter size between AA and AB was non-significant (P>0.05) in Jining Grey goats. For primer P2, two genotypes (DD and DE) were detected in Jining Grey goats, Liaoning Cashmere goats and Boer goats, and only genotype DD was detected in Angora goats. Sequencing revealed two mutations (52G-->A and 122G-->A) of PRLR gene in the genotype DE in comparison to the genotype DD. The former mutation did not cause any amino acid change, and the latter mutation resulted in an amino acid change of Arg-->Gly. The difference of LSM for litter size between DD and DE was non-significant (P>0.05) in Jining Grey goats. For primer P4, two genotypes (FF and FG) were detected in Jining Grey goats, two genotypes (FF and GG) were detected in Liaoning Cashmere goats, only genotype FF was detected in Boer goats, and three genotypes (FF, FG and GG) were detected in Angora goats. Sequencing revealed one mutation (143A-->G) of PRLR gene in the genotype GG in comparison to the genotype FF, and this mutation resulted in an amino acid change of Met-->Val. The Jining Grey does with genotype FG had 0.76 (P< 0.05) kids more than those with genotype FF. These results preliminarily showed that the PRLR gene is either a major gene that influences the prolificacy of Jining Grey goats or a molecular marker in close linkage with such a gene.