The Drosophila Trpm channel mediates calcium influx during egg activation

Significance A rise in intracellular free calcium is a conserved feature of the egg-to-embryo transition in almost all animals. In Drosophila , as in vertebrates, the rise starts at one end of the oocyte and then travels across the egg in a wave. The Drosophila calcium rise is mediated by an influx of calcium due to the action of mechanically gated ion channels. Here, we identify the ion channel that is critical for the calcium entry as Trpm. Trpm is the ortholog of a channel recently shown to mediate the postfertilization calcium influxes needed to sustain calcium oscillations in fertilized mouse eggs, suggesting a deep homology despite species differences in the trigger for egg activation.