Mating Increases CHST10 Activity in the Oviductal Mucosa to Induce the Synthesis of HNK-1 Glycoproteins: The Possible Role of HNK-1-ALDH9A1 in Sperm–Oviduct Interactions

Previously, we reported that mating induces an early transcriptional response in the oviductal mucosa of rats. The functional category ‘cell-to-cell signaling and interaction’ was overrepresented in this gene list. Therefore, in the present study, we describe the role of one of these genes, carbohydrate sulfotransferase 10 (Chst10), in the oviductal mucosa. CHST10 participates in the synthesis of the carbohydrate moiety HNK-1, which mediates cell-to-cell interactions. Using 1D western blot and sulfotransferase assays, we showed that mating increased the protein level and activity of CHST10 in the oviductal mucosa at 3 h after stimulation. A 2D western blot assay and mass spectrometry were used to identify the novel HNK-1 glycoproteins ALDH9A1, ALDOA and FHL1 in the oviductal mucosa, and we showed that mating induces the synthesis of their acidic variants. Interestingly, in the utero-tubal junction (UTJ), acrosome-reacted sperm are in close contact with HNK-1-ALDH9A1 regions, and acrosome-intact sperm are in close contact with other regions in which HNK-1 and ALDH9A1 do not colocalize. Furthermore, vaginocervical stimulation applied to unmated rats increases the mRNA level of Chst10 in the oviductal mucosa. In conclusion, mating increases the activity of CHST10 in the oviductal mucosa, which in turn induces the synthesis of acidic variants of ALDH9A1 and FHL1 via HNK-1 glycosylation. In the UTJ, HNK-1-ALDH9A1 can control the quality of the sperm arriving at the fertilization site, since we detected acrosome-reacted sperm in close contact with this glycoprotein, a finding that merits further research to propose the use of HNK-1-ALDH9A1 in the selection of sperm in procedures of assisted reproduction. Finally, the sensorial component of mating could regulate events occurring in the oviductal mucosa early after mating.