Identification of differentially expressed genes and pathways in the post-ovulatory ampulla of cyclic pigs through a transcriptomics approach.

Background: Information on global transcriptomic changes in the porcine ampulla after ovulation is crucial for understanding of oviductal physiology at the molecular level. The objective of the present study was to investigate the differentially expressed genes (DEGs) and signalling pathways regulating the functionality of ampulla in pigs post-ovulation.

Methods and results: The RNA-sequencing of the post-ovulatory ampulla (POA) and early luteal ampulla (ELA) tissues was conducted using Illumina NextSeq2000. The R package NOISeq was used to obtain significantly differentially expressed genes (DEGs) with the probability of differential expression (1-FDR) value ≥ 0.95 and log₂ fold change (log₂FC) ≥ 1, which revealed 817 DEGs (657 up- and 160 down-regulated) in the POA vs. ELA group comparison. These DEGs were functionally annotated with various gene ontology terms like sterol biosynthetic process, growth, cell migration, and Reactome pathways like signal transduction, metabolism, and cell cycle, indicating key role of these molecular events in POA. The WNT, TNFR2 non-canonical NF-kB, and hedgehog signalling pathways along with the activation of the immune system process, were enriched in the POA vs. ELA group, which indicates their role in cell-cell interactions and cell fate determination in remodelling the oviductal microenvironment during transition from estrogen to progesterone domination. The highly connected upregulated hub genes ESR1, RAD51, YARS1, TYMS and CDK2 can be regarded as key regulatory factors in synchronizing the changes in POA at the molecular level in the oviduct.

Conclusion: The present study revealed several DEGs, signalling pathways and novel modulatory factors associated with the ampullary physiology during early embryonic development in the POA, which may influence fertility and litter size in pigs.