Activation of motility and chemotaxis in the spermatozoa

Sperm motility and chemotaxis are important early steps in the interaction between sperm and oocytes during fertilization. Understanding these processes is essential for their basic biological and clinical applications. This review outlines advances in understanding the molecular mechanisms of sperm activation and chemotaxis over the past two decades.

The review focuses on the molecular pathways of Ca²⁺ signaling and the role of the CatSper channel involved in this signaling, and examines the comprehensive mechanisms that regulate sperm motility in aquatic invertebrates, fish, and mammals.

Sperm are activated by environmental changes (e.g., pH and osmolality) and egg-derived factors. CatSper channels mediate Ca²⁺ influx and regulate cell motility and chemotaxis. In addition to Ca²⁺, cAMP and membrane potential are also involved in the regulation of sperm motility. Alternative pathways exist in species lacking CatSper, highlighting the diversity of sperm activation mechanisms.

There has been significant progress in understanding sperm motility regulation mediated by Ca²⁺, notably with CatSper, but the molecular mechanisms of other factors remain unclear. Future research should focus on species lacking CatSper to uncover commonalities and diversity in sperm motility regulation using genome editing and transcriptomic analyses.