Characterization of Porcine Matrix Metalloproteinase 23 (pMMP-23) Gene and Its Association with Litter Size Traits

The matrix metalloproteinase 23 （MMP-23）, which might play a role in ovulation in mammals, was one of the promising candidate genes for litter size traits in pigs. In the present research, partial sequence of porcine MMP-23 （pMMP-23） gene, including exons 2-8 （GenBank： EU360790）, was obtained. Real-time PCR analysis revealed that pMMP-23 gene was highly expressed in ovary. PCR-Sau3A I-RFLP and PCR-Acc II-RFLP assay were established to detect a C/T mutation in exon 3 （EU360790： g. 269C〉T） and an A/G mutation in exon 4 （EU360790： g. 505A〉G）, respectively. Association study for these two SNPs with litter size was assessed in three independent populations （Minzhu, Landrace I and Landrace II）. Statistical analysis demonstrated that for second and subsequent litters, TT sows produced more TNB than CC pigs in Landrace breed （P〈0.05） at g. 269C〉T locus, and the additive effect was significant （P〈0.05）; GG sows produced more TNB and NBA than AA pigs in Minzhu （P〈0.01） and Landrace breeds （P〈0.05） at g. 505A〉G locus, and the additive effect was significant （P〈0.01 or P〈0.05）. Our study suggested that the pMMP-23 gene might be a novel candidate gene for litter size traits, and g. 505A〉G locus might be a useful molecular marker for marker assisted selection （MAS）.

Identification of Novel Polymorphisms in Porcine Ring Finger Protein 4 and Matrix Metalloproteinase 9 Genes and Association Analysis with Litter Size Traits

Reproduction trait plays an important role in pig production. Identification of molecular markers that are linked to litter size may contribute to the genetic development of porcine reproduction traits. In this study, porcine ring finger protein 4 （pRNF4） and Matrix metalloproteinase 9 （pMMP-9） were selected as candidate genes on the basis of their physiological roles in reproduction. Two single-nucleotide polymorphisms （416C〉T in pRNF4 and - 1257G〉A in pMMP-9） that could be detected by PCR restriction fragment length polymorphism （PCR-RFLP） were discovered and tested for statistical associations with litter size traits in three populations. For 416C〉T, TT genotype was associated with a significantly higher （p〈0.05） number of live births than those recorded for CC sows and the additive effect was significant （p〈0.05） in Qingping and Min Pigs populations in later parities. For -1257G〉A, inconsistent results were found in three populations. The results suggested that T allele in pRNF4 gene might confer a high prolificacy in breeding and further studies were needed to confLrm the results.