Ion channels in sperm physiology

Fertilization is a matter of life or death. In animals of sexual reproducti on, the appropriate communication between mature and competent male and fem ale gametes determines the generation of a new individual. Ion channels are key elements in the dialogue between sperm, its environment, and the egg. Components from the outer layer of the egg induce ion permeability changes in sperm that regulate sperm motility, chemotaxis, and the acrosome reactio n. Sperm are tiny differentiated terminal cells unable to synthesize protei n and difficult to study electrophysiologically. Thus understanding how spe rm ion channels participate in fertilization requires combining planar bila yer techniques, in vivo measurements of membrane potential, intracellular C a2+ and intracellular pH using fluorescent probes, patch-clamp recordings, and molecular cloning and heterologous expression. Spermatogenic cells are larger than sperm and synthesize the ion channels that will end up in matur e sperm. Correlating the presence and cellular distribution of various ion channels with their functional status at different stages of spermatogenesi s is contributing to understand their participation in differentiation and in sperm physiology. The multi-faceted approach being used to unravel sperm ion channel function and regulation is yielding valuable information about the finely orchestrated events that lead to sperm activation, induction of the acrosome reaction, and in the end to the miracle of life.