Sperm defender has second role

A protein that scientists suspect defends sperm and other cells from microbes also guides the maturation of sperm, a new study concludes.

Before a sperm cell can fertilize an egg, it must pass out of a testicle and through a coiled tube called the epididymis. It’s during this passage that sperm gain their full capacity to swim and fertilize eggs, although what triggers this maturation remains murky.