FRIDAY, Oct. 17 (HealthDay News) -- Infertility in some men may be explained by the lack of a protein involved in producing the spikes in calcium concentration that normally occur in the egg upon fertilization, according to research published online Oct. 16 in the Journal of Clinical Investigation.
Sook-Young Yoon, from the University of Massachusetts in Amherst, and colleagues investigated the ability of sperm from seven men who repeatedly failed intracytoplasmic sperm injection to induce cytosolic [Ca2+] oscillations in mouse eggs, which normally occurs after egg activation and initiates embryo development.
The researchers found that sperm from three of these infertile men were unable to induce [Ca2+] oscillations and egg activation. Further investigation showed that the sperm lacked the phospholipase C zeta-1 (PLCZ1) enzyme normally present in the equatorial region of wild-type sperm heads. PLCZ1 initiates the phosphoinositide cell signaling pathway and had been implicated in producing the [Ca2+] oscillations, according to the authors. Replacing the enzyme restored the ability of the defective sperm to induce egg activation.
"Together, our results indicate that the inability of human sperm to initiate [Ca2+]i oscillations leads to failure of egg activation and sterility and that abnormal PLCZ1 expression underlies this functional defect," Yoon and colleagues conclude.
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