Several previous studies have tried to elucidate the complex signaling phenomenon underlying the mammalian oocytes activation. Intracellular Ca²⁺ oscillations triggered by the penetrated spermatozoa have been found to be crucial for both oocyte activation as well as normal embryo development. Now, a collaborative study conducted by US and UK researchers has reported that the abnormal expression of phospholipase Czeta 1 (PLCZ1) sperm protein is linked to the inability of the human sperm to induce Ca²⁺ oscillations, leading to failure of egg activation and sterility. Read the full story