A peer-reviewed mouse study found that two sperm enzymes make overlapping contributions to the calcium pulses that activate an egg. Loss of both left males sterile, while the absence of one changed the signal’s timing or strength. The work helps explain why a fertilization signal can persist when its main known trigger is missing.
Male mice lacking both sperm enzymes in a new PLOS Biology experiment were sterile. Their sperm failed to produce the repeated calcium rises normally involved in activating an egg. A residual single rise was insufficient for activation in the tested settings. The peer-reviewed paper, published on 6 November, places the timing and repetition of this cellular signal at the center of the fertilization finding.[1]
The two proteins are phospholipase C enzymes, which participate in cellular signaling. The form called PLCζ1 is the main known trigger of the calcium oscillations. When it was absent, oscillations still occurred, but began later and were less frequent. Higher levels of the second form, PLCδ4, accompanied that partial compensation. Removing PLCδ4 alone also delayed the signal and impaired fertilization-related outcomes.[1]
These calcium pulses help launch the egg’s developmental program. The partially overlapping enzyme contributions help explain why the loss of the principal trigger alone left some fertility in mice. Species differences and other sperm–egg components limit translation to people, and the experiment supplies no human treatment result. The authors also leave open a possible indirect contribution from another phospholipase to the mouse response.[1]
