Preliminary Research On Polymorphisms In Prolactm (PRL)and Prolactin Receptor (PRLR) Gene Of Yili Horse And Its Hybrids

Prolactin (PRL) is the one of the important hormone that associated with mammals lactation performance,the physiological functions of prolactin were mediated through prolactin receptor (PRLR).The PRL and PRLR gene were the most important candidate genes that identified by their ability to affect lactation of diary cows.But,there are no any information about the single nucleotide mutations of PRL and PRLR gene whether affects on lactation performance of horse.In this study the polymorphisms of prolactin and prolactin receptor genes in the Yili horse, New Kirgiz horse and its hybrids were analyzed by the technique of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and DNA sequencing. The five exons of PRL gene and eight of prolactin receptor gene were detected in the three populations. It aims to get molecular genetic informations and clear the single nucleotide mutation positions of prolactin and prolactin receptor gene of horse. The objectives of the present study lay the foundation for effects of gene mutations on performance of lactation of horse.The results were as follows:(1)The result revealed that no polymorphism was detected on the exonl,2,3and4of PRL gene.(2)For the first time, we found two single nucleotide polymorphisms (SNPs)(T591G and C654T) in exon5of PRL gene of horse. All of these were synonymous. Three alleles, A, B and C, were found in this locus. The frequencies of the dominant allele were0.760and0.785in the Yili horse and its Hybrids.(3)On the PRLR gene, ten SNPs were detected on the exon4,5and10, but not on the exon3,6,7,8and9.(4) A transition (C156T)was detected at156bp on the exon4of PRLR gene. The frequencies of the dominant allele were0.820and0.885in Yili horse and its hybrids. This mutation did not change of encoding amino acid.(5) A transversion (A312G) was detected on the exon5of PRLR gene and it was synonymous.The frequencies of the dominant allele were0.7and0.785, effective numbers of alleles (Ne) were1.724and1.8546.(6) Eight SNPs (A1062G, C1083T, T1226G, G1233A, C1297A, G1764C, T1778A and A1794T) were detected on the exon10of PRLR gene. Among these mutations, A1062G, C1083T, G1233A and A1794T were synonymous. Amino acids changed by the four missense mutations (T1226G, C1297A, G1764C and T1778A) were H409P, H427N, Q588H and1593K, respectively. Statistical results showed that all polymorphism sites on the PRL and PRLR genes of Yili horse and its hybrids were consistent with Hardy-Weinberg equilibrium.(7)Through the analysis of genotype and milk yield in the fifth exon of PRL gene, the Yili horses with AA genotype produced more milk of850g/d than the BB genotype.There were significant differences between milk yield and different genotypes of Hybrid horse at mutant site of PRLR exon5.Both of the Yili horse and Hybrids were significant differences between milk yield and different genotypes at mutant sites of PRLR exon10-3and10-5.The study results indicated that both of the PRL and PRLR genes exist SNPs in Yili horse and its hybrids. A total of12SNPs were found, and finally resulted in4amino acid changed. Abundant mutations exist on the exon10of PRLR gene.This mutations whether affects on the functions of the PRL and PRLR need further research.