One of two papers that identify a new pathway by which calcium triggers oocyte fertilization. Previous work has shown a critical role for the calcium-regulated kinase CaMKII. But new work from the Ohsumi and Hunt laboratories shows that, in parallel, calcium-mediated transient activation of a phosphatase, calcineurin, is needed to release oocytes from a cell cycle arrest after fertilization. The Hunt group also identifies a second wave of phosphatase activity that acts in mitosis.
