The sperm that successfully fertilizes an egg triggers a series of events, known collectively as egg activation, that are considered the first step in the initiation of embryo development. Detection of egg activation is used by clinics to determine whether an in vitro fertilization procedure (a process whereby egg cells are fertilized by sperm in a test tube) has been successful. The sperm of some patients who repeatedly fail the in vitro fertilization technique ICSI, which is used to treat male factor infertility, fail to induce egg activation, and the patients are therefore sterile. Rafael Fissore and colleagues, at the University of Massachusetts, Amherst, have now uncovered one molecular defect underlying such sterility: the sperm lack detectable levels of the protein PLC, zeta-1.
