The SNPs Analysis Of Pit-1 Gene Partial CDNA Sequence In Seven Pig Breeds

Growth rate is one of the main target traits selected in swine breeding and identification of candidate genes associated with growth traits will be very important on theoretical and practical values. Pit-1, a member of the POU-domain family of genes, is a positive regulatory factor of growth hormone , prolactin , and thyrotroph-stimulating hormone p subunil in several mammals. It plays important regulatory roles in developmental processes.In this study, the polymorphisms of porcine Pit-1 encoding gene in 483 pigs including Min pig , Sanjiang white pig , Number I Junmu , Landrace , Yorkshire , Duroc and Double muscled Yorkshire were detected by PCR-SSCP with four different pairs of primers. Only products amplified by the second primer pairs showed polymorphisms and three genotypes were detected in different porcine breeds, namely TT, TC and CC respectively. By cloning and sequencing to two homozygote amplified fragments and comparisons with cDNA sequence published on Genebank dababase , we found a C to T transversion (600) in exon 4. This point mutation did not change the encoded amino acid residue.In breeds of Min pig, Sanjiang white pig, Landrace, Yorkshire, Duroc and Double muscled Yorkshire, the frequencies of T allele increased progressively, and the average daily gains in these breeds also rised in this order .But Number I Junmu is an exception. With the less sample population(29) , the frequence obtained from Number I Junmu coundn't represent the real fact.X2 test showed there are significant differences among these breeds(P<0.01). T Test showed that differences among Min pig and Sanjiang white pig with other five breeds were highly significant (P<0.01), differences among Landrace with Yorkshire and Duroc were significant (0.05 0.05). Min pig is our local breed, and Sanjiang White was breed by crossing between Min pig and Landrace and backcrossing with Landrace. They have lower growth rate than foreign breeds such as Large Yorkshire, Landrace, Duroc and double-muscled Yorkshire. So there was a trend that C allele maybe come from our local pig breeds , while T allele associated with high growth rate. Thus T allele of Pit-1 gene could be used as one of selective markers of high growth rate in pig breeding, and this study provided a basis for marker assisted selection breeding.