Postcopulatory transcriptional profiling of the murine uterotubal junction identifies potential sperm selection mediators

The female reproductive tract (FRT) is composed of distinct sections which all take part in the sperm selection processes that occur after copulation. Among the different sections, the uterotubal junction (UTJ) presents a significant obstacle to sperm and is a major site of sperm selection. This selection is based not only on motility and morphology, but on the presence and conformation of specific sperm surface proteins. In the mouse model, a disintegrin and metallopeptidase domain 3 and other sperm surface proteins have been identified as being critical for passage through the UTJ, however, the potential female counterparts of these proteins are still unknown. Our study takes a transcriptomics approach, through an RNAseq analysis of the FRT tissue following copulation in female mice in estrus, to uncover candidate sperm surface protein interactors on the UTJ epithelium. Our results showed 240 genes with higher expression specifically in the UTJ in response to the presence of semen. The UTJ exhibited an upregulation of extracellular matrix-related genes that was not found in the uterus or oviduct following copulation. A list of candidate genes was generated using further bioinformatics analysis, and two candidates, galectin 3 (LGALS3) and integrin alpha 8 (ITGA8), were selected for immunofluorescence and western blot analysis. Both LGALS3 and ITGA8 were identified on the surface of the UTJ epithelium, with a higher abundance of LGALS3 in the UTJ of copulated females compared to non-copulated animals. This suggests a role of these candidates in the selection processes occurring in the murine UTJ, with prospective future usage in the refinement of artificial reproduction technologies.