Analysis of Ca2+-mediated sperm motility to evaluate the functional normality of the sperm-specific Ca2+ channel, CatSper

Abstract

Ca2+ is a key secondary messenger that modulates sperm motility by tuning flagellar movement in various species. The sperm-specific Ca2+ channel, CatSper, is a primary Ca2+ gate that is essential for male fertility in mammals. CatSper-mediated Ca2+ signaling enables sperm to develop hyperactivated motility and fertilize the eggs in the female tract. Therefore, altered CatSper function compromises the entry of Ca2+ into the sperm, followed by impairing hyperactivation and male fertility. However, methods to evaluate the function of the CatSper channel are limited to patch clamping and functional imaging using Ca2+ dye. Previous studies have revealed that various parameters for sperm motility are highly correlated with intracellular Ca2+ levels in mouse. Here, I cover a step-by-step protocol to analyze the change in Ca2+-mediated sperm motility by using computer-assisted semen analysis (CASA) to evaluate the functional normality of the CatSper channel in sperm. This approach analyzes sperm motility parameters during intracellular Ca2+ chelation followed by in vitro capacitation to recover intracellular Ca2+ via the activated CatSper channel. Thus, this Ca2+-handling method is handy and could be broadly applied in reproductive biology labs and clinics that have CASA equipment to examine the functional normality of the CatSper channel.