Molecular cloning, tissue expression and association of porcine NR4A1 gene with reproductive traits

Nuclear receptor subfamily 4, group A, member 1 (NR4A1), other aliase NGFI-B, is an immediate-early gene that encodes an orphan nuclear receptor, which play a potential role in the ovulatory process. In this study, a 4,870 bp fragment covered the complete coding region (CDS) and its unique intron sequences of porcine NR4A1 gene was obtained. The reverse transcriptase-polymerase chain reaction (RT-PCR) indicated that NR4A1 was highly expressed in ovary, uterus, kidney, heart but at very low level in oviduct and not expressed in other tissues. Compared the sequence of CDS and its unique intron of Large White and Meishan pigs, a A/G mutation in intron 5 was found and a PCR-Dde1-RFLP genotyping assay was developed. Association of the SNP and litter size was assessed in two populations [purebred Large White and an experimental synthetic Line (DIV) sows]. Statistical analysis demonstrated that, in the first parity, AG animals in experimental synthetic Line (DIV) sows had 1.805 more piglets born compared to the GG animals (P<0.05). For all parities, in the purebred Large White pigs, those with the GG genotype had an additional 0.877 piglets born and 0.780 piglets born alive compared to the AA animals (P<0.05), those with the AG genotype had additional 0.780 piglets born compared to the AA animals (P<0.05). In addition, significant additive effect of 0.438±0.182 piglets/litter and 0.368±0.165 piglets/litter on piglets born and piglets born alive were detected in the purebred Large White lines (P<0.05), respectively. Therefore, NR4A1 gene was significantly associated with litter size in two populations and could be a useful molecular marker in selection for increasing litter size in pigs.