(A) CatSper channels in the tail of sperm are glycosylated during maturation in the male epididymis. (B) Differences between sperm visualized in the female reproductive tract 8 hours post coitus. Sperm visualized near the uterotubal junction (the place where the uterus and the oviduct tubes meet, left) exhibited an intact acrosome, high levels of tyrosine phosphorylation (pY) in tail proteins, and degraded CatSper channels. Sperm in the isthmus (the part of the tube through which eggs pass from an ovary closest to the uterus, center) have already started their acrosome reaction, have intermediate levels of tyrosine phosphorylation in proteins in their tails, and intermediate levels of CatSper degradation. Finally, sperm in the ampulla (the part of the tube through which eggs pass closest to the ovary, where fertilization usually takes place) have reacted acrosomes, intact CatSper channels, and low levels of tyrosine phosphorylation in their tail proteins.
Figure created in BioRender.com.