Identification and characterization of an oocyte factor required for sperm decondensation in pig

摘要

Mammalian oocytes possess factors to support fertilization and embryonic development, but knowledge on these oocyte-specific factors is limited. In the current study, we demonstrated that porcine oocytes with the first polar body collected at 33?h of in vitro maturation sustain IVF with higher sperm decondensation and pronuclear formation rates and support in vitro development with higher cleavage and blastocyst rates, compared with those collected at 42?h ( P <0.05). Proteomic analysis performed to clarify the mechanisms underlying the differences in developmental competence between oocytes collected at 33 and 42?h led to the identification of 18 differentially expressed proteins, among which protein disulfide isomerase associated 3 (PDIA3) was selected for further study. Inhibition of maternal PDIA3 via antibody injection disrupted sperm decondensation; conversely, overexpression of PDIA3 in oocytes improved sperm decondensation. In addition, sperm decondensation failure in PDIA3 antibody-injected oocytes was rescued by dithiothreitol, a commonly used disulfide bond reducer. Our results collectively report that maternal PDIA3 plays a crucial role in sperm decondensation by reducing protamine disulfide bonds in porcine oocytes, supporting its utility as a potential tool for oocyte selection in assisted reproduction techniques.