Insertion of 275-bp SINE into first intron of PDIA4 gene is associated with litter size in Xiang pigs

The aim of the study was to investigate the SINE polymorphism in Xiang, Kele, Qianbei black, Jiangkouluobo, Large White, and Duroc pig breeds. The PCR based detection method was conducted to identify the short interspersed nuclear element (SINE) polymorphism in the PDIA4 gene. There were greater frequencies of the SINE−/− genotypes in Xiang pigs (55.9%) as compared with other pig breed groups. There was an association between this 275 bp SINE polymorphism and litter size (P = 0.003). The homozygous SINE+/+ genotype of the PDIA4 gene had a 1.45-piglets larger litter sizes compared to those with the homozygous SINE−/− genotype. Furthermore, there were assessments of mRNA and protein abundances as a result of PDIA4 gene expression in the ovaries of Xiang pigs for the three different SINE genotypes, and the results indicated that relative abundances of PDIA4 mRNA and protein was greater for the SINE−/− and SINE−/+ genotypes compared with the SINE+/+ genotype (P < 0.05). These findings suggested that the 275 bp SINE polymorphism might change the expression of the PDIA4 gene and could be used as a candidate DNA marker for the selection for litter size in Xiang pigs.