The Association of an SNP in the EXOC4 Gene and Reproductive Traits Suggests Its Use as a Breeding Marker in Pigs

SIMPLE SUMMARY: The exocyst complex component 4 (EXOC4) gene is essential for the growth and development of humans and animals. However, the molecular mechanisms between EXOC4 and the reproductive performance of pigs is yet to be elucidated. The findings of our study revealed that single-nucleotide polymorphism (SNP) rs81471943 (C/T) was located in the EXOC4 gene by Sanger sequencing and PCR-restriction fragment length polymorphism (PCR-RFLP). We then analyzed the relationship between this SNP in EXOC4 and reproductive traits. We found that CC was the most frequent genotype on number of piglets born alive (NBA), litter weight at birth (LWB), number of piglets weaned (NW), and litter weight at weaning (LWW). Finally, 5′-deletion and luciferase assays showed a positive transcription regulatory element in the EXOC4 promoter. Therefore, we predicted that −1781G/A might regulate the expression of EXOC4 by affecting the potential binding of transcription factors P53, E26 transformation specific sequence -like 1 transcription factor (ELK1), or myeloid zinc finger 1 (MZF1). ABSTRACT: In mammals, the exocyst complex component 4 (EXOC4) gene has often been reported to be involved in vesicle transport. The SNP rs81471943 (C/T) is located in the intron of porcine EXOC4, while six quantitative trait loci (QTL) within 5–10 Mb around EXOC4 are associated with ovary weight, teat number, total offspring born alive, and corpus luteum number. However, the molecular mechanisms between EXOC4 and the reproductive performance of pigs remains to be elucidated. In this study, rs81471943 was genotyped from a total of 994 Duroc sows, and the genotype and allele frequency of SNP rs81471943 (C/T) were statistically analyzed. Then, the associations between SNP rs81471943 and four reproductive traits, including number of piglets born alive (NBA), litter weight at birth (LWB), number of piglets weaned (NW), and litter weight at weaning (LWW), were determined. Sanger sequencing and PCR restriction fragment length polymorphism (PCR-RFLP) were utilized to identify the rs81471943 genotype. We found that the genotype frequency of CC was significantly higher than that of CT and TT, and CC was the most frequent genotype for NBA, LWB, NW, and LWW. Moreover, 5′-deletion and luciferase assays identified a positive transcription regulatory element in the EXOC4 promoter. After exploring the EXOC4 promoter, SNP −1781G/A linked with SNP rs81471943 (C/T) were identified by analysis of the transcription activity of the haplotypes, and SNP −1781 G/A may influence the potential binding of P53, E26 transformation specific sequence -like 1 transcription factor (ELK1), and myeloid zinc finger 1 (MZF1). These findings provide useful information for identifying a molecular marker of EXOC4-assisted selection in pig breeding.