| Abstrakt: |
Simple Summary: After sperm–oocyte fusion, oocytes are activated by a sperm factor for fertilization and embryo development success. Evidence proposes that sperm-borne phospholipase C Zeta 1 (PLCZ1) as an activating factor. The alteration of the gene or protein expression of PLCZ1 results in low or no fertility. In human assisted reproduction, PLCZ1 characterization is of essential importance when oocyte activation failures are linked to male infertility. However, little is known about the importance of PLCZ1 for in vivo and in vitro fertility outcomes in cattle and horses, particularly as the commercial use of assisted fertilization grows. In horses, intracytoplasmic sperm injection (ICSI) is the elective method for assisted fertilization. Sperm PLCZ1 amount exhibits a large variation from stallion to stallion which can influence fertility outcomes. Stallion sperm samples showing low PLCZ1 consistently result in lower fertility after ICSI. In contrast, ICSI is not efficient in cattle due to the inconsistent ability of bull sperm to activate bovine oocytes. Interestingly, the experimental microinjection of exogenous PLCZ1 is able to rescue oocytes that failed to activate, even reaching live birth. PLCZ1 has the potential to be used as a diagnostic and predictive tool for sperm-fertilizing capability and therapeutic treatment for oocyte failure under assisted fertilization. Phospholipase C Zeta 1 (PLCZ1) is considered a major sperm-borne oocyte activation factor. After gamete fusion, PLCZ1 triggers calcium oscillations in the oocyte, resulting in oocyte activation. In assisted fertilization, oocyte activation failure is a major cause of low fertility. Most cases of oocyte activation failures in humans related to male infertility are associated with gene mutations and/or altered PLCZ1. Consequently, PLCZ1 evaluation could be an effective diagnostic marker and predictor of sperm fertilizing potential for in vivo and in vitro embryo production. The characterization of PLCZ1 has been principally investigated in men and mice, with less known about the PLCZ1 impact on assisted reproduction in other species, such as cattle and horses. In horses, sperm PLCZ1 varies among stallions, and sperm populations with high PLCZ1 are associated with cleavage after intracytoplasmic sperm injection (ICSI). In contrast, bull sperm is less able to initiate calcium oscillations and undergo nuclear remodeling, resulting in poor cleavage after ICSI. Advantageously, injections of PLCZ1 are able to rescue oocyte failure in mouse oocytes after ICSI, promoting full development and birth. However, further research is needed to optimize PLCZ1 diagnostic tests for consistent association with fertility and to determine whether PLCZ1 as an oocyte-activating treatment is a physiological, efficient, and safe method for improving assisted fertilization in cattle and horses. [ABSTRACT FROM AUTHOR] |
