Polymorphism of Five SNPs in Exon 10 of Growth Hormone Receptor Gene in Guizhou Pony(Equus caballus)

To explore the reason for the slow growth of Guizhou pony,sequences of exon 10 in GHRgene were cloned from the genome of Guizhou pony by polymerase chain reaction(PCR)and gene cloning methods.Distribution of 5single nucleotide polymorphism(SNP)sites was determined by allele-specific PCR(AS-PCR)and single-strand conformation polymorphism(SSCP)methods.Taking Ili horse as control,the relationship between the genotypes of GHRand body sizes of Guizhou pony and Ili horse was calculated based on population genetics and bioinformatics algorithms.The results showed that a total of 10 haplotypes of exon 10 of GHR gene were sequenced from Guizhou pony,in which contained 10 SNP sites.Among them,5sites,1028,1267,1471,1697 and 1732,changed the amino acid residues of GHR.Frequencies of 3sites,1028,1267 and 1471,were tested by AS-PCR method.Compared with Ili horse,allele A at site 1028 was dom-inant and related with the lower rump height and higher cannon circumference in Guizhou pony.The percentage of allele E at 1471 site in Guizhou pony was higher than that in Ili horse and related to higher chest girth ratio of pony.Heterozygous genotypes of 1697 and 1732sites were detected from the shortest male pony with 106 cm in height,6years old.The V343 Achange resulted from 1028 site located in the ubiquitin-dependent endocytosis(UbE)motif and might affect the GHR internalization and degradation.Changes at S491 G,Y566Cand R578 Gsites resulted from SNP sites of 1471,1697 and 1732,might directly or indirectly impact the phosphorylation of GHR and influence the activation of signal transduction pathways.It suggested that the polymorphisms in exon 10 of GHRgene might have an effect on the growth and development of Guizhou pony.