Ca²⁺ oscillations and sperm factors at fertilization in mammals

Abstract

At fertilization in mammals, the spermatozoon triggers a series of Ca²⁺ oscillations that are essential for activating the oocyte. The reason why the spermatozoon triggers Ca²⁺ oscillations, as opposed to a single Ca²⁺ increase, is unknown. However, there is evidence that more than one Ca²⁺ increase is required for efficient rates of pronuclear formation. In addition, the pattern of Ca²⁺ oscillations may affect later development. It is not known how the spermatozoon triggers Ca²⁺ release in the oocyte, but it may act by introducing a cytosolic factor after gamete membrane fusion has taken place. This factor is characterized by its ability to cause Ca²⁺ oscillations and is referred to as an oscillogen. The protein components that make up the sperm oscillogen remain unclear.