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Identification and characterization of an oocyte factor required for sperm decondensation in pig. Li J 2014 et al.
Mammalian oocytes possess factors to support that 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 in vitro fertilization with higher sperm decondensation and pronuclear formation rates and support in vitro development with higher cleavage and blastocyst rates, compared to those collected at 42 h (p<0.05). Proteomic analysis performed to calrify 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. Maternal PDIA3 inhibition via antibody injection disrupted sperm decondensation, and conversely, overexpression of PDIA3 in oocytes improved sperm decondensation. In addition, sperm decondensation failure in PDIA3 antibody-injectecd oocytes was rescued by dithiothreitol (DTT), a commonly used disulfide bond reducer. Our results collectively demonstrate 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.
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Increased expression of ERp57 in rat oocytes during meiotic maturation is associated with sperm-egg fusion. Liu Y 2014 et al.
Oocyte meiotic maturation is a developmental transition that starts during germinal-vesicle breakdown and ends at the arrest in metaphase of meiosis II. This transition is associated with changes to both the proteins that are synthesized and the abundance/distribution of post-translational modifications that are crucial for subsequent fertilization and embryogenesis. Here, we isolated and cultured rat oocytes in vitro during both metaphase of meiosis I (MI) and meiosis-II (MII) stages, respectively, and then compared their proteomic profiles by high-resolution, two-dimensional gel electrophoresis (2DE) followed by mass spectrometry. We found that the expression of five proteins was up-regulated while six proteins were down-regulated when comparing MI to MII oocytes. The expression of ERp57, an endoplasmic reticulum chaperone, underwent a dramatic increase between MI and MII oocytes, and became concentrated in a dome-shaped area of the cell surface within the microvillar region. A similar profile was observed during spermatogenesis, and sperm ERp57 eventually localized to the head and flagellum surfaces, finally ending in the equatorial region of acrosome-reacted sperm. Given the localization pattern, we tested and found that a polyclonal antiserum created against recombinant rat ERp57 significantly inhibited spermatozoa from penetrating zona pellucida-free oocytes without affecting either sperm motility or the acrosome reaction. These results indicate that ERp57 expression on oocytes, and possibly sperm, plays an important physiological role during sperm-egg fusion. Mol. Reprod. Dev. ? 2014 Wiley Periodicals, Inc.
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Identification of Hepsin and Protein Disulfide Isomerase A3 as Targets of Gelatinolytic Action in Rat Ovarian Granulosa Cells During the Periovulatory Period. Rosewell K et al. The matrix metalloproteinase (MMP) family plays a role in the ovulatory process as MMP inhibitors block oocyte release. However, little is known about the mechanisms by which the MMPs act to impact ovulation. The present study investigated the degradomic actions of the gelatinases, MMP2 and MMP9, by identifying gelatinolytic targets in periovulatory granulosa cells. Granulosa cells were collected from immature rats 48 h after equine chorionic gonadotropin treatment and were cultured with human chorionic gonadotropin (hCG) in the absence or presence of a specific MMP2/9 inhibitor ((2R)-2-[(4-Biphenylylsulfonyl)amino]-3-phenylpropionic acid) for an additional 24 h. The conditioned media was analyzed for gelatinolytic activity, progesterone, and peptide profiles. Gelatinolytic activity and progesterone were induced in response to hCG, however, there was no difference in progesterone between cells treated with or without the inhibitor. Peptide fragments of proteins altered in the presence of the gelatinase inhibitor were identified by 2D gel electrophoresis and mass spectrometry. Protein disulfide isomerase A3 (PDIA3), which plays a role in protein folding, was identified as a peptide that decreased in the presence of inhibitor while the serine protease hepsin, was found to increase with inhibitor treatment. Subsequent experiments established that PDIA3 and hepsin were targets of MMP2/9 action by cleavage with MMP2 and Western blot analysis respectively. Additionally, hepsin was identified as a gelatinolytic target in ovarian cancer cells. In the present study, proteomics has identified proteins that may be involved in novel ways in the complex cascades that are mediated by gelatinolytic MMPs during the periovulatory period.
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Distribution of protein disulfide isomerase during maturation of pig oocytes. Ohashi Y et al. Oocyte maturation in mammals is characterized by a dramatic reorganization of the endoplasmic reticulum (ER). In mice, the ER forms accumulations in the germinal vesicle (GV) stage and distinctive cortical clusters in metaphase II (MII) of the oocyte. Multiple evidence suggests that this ER distribution is important in preparing the oocyte for Ca(2+) oscillations, which trigger oocyte activation at fertilization. In this study, we investigated the time course and illustrated the possible functional role of ER distribution during maturation of porcine oocytes by immunostaining with protein disulfide isomerase (PDI). PDI forms clusters in the cytoplasm of oocytes. After immunostaining, PDI clusters were identified throughout the cytoplasm from the GV to metaphase I (MI) stage; however, at the MII stage, the PDI formed large clusters (1-2 ?m) in the animal pole around the first polar body. PDI distribution was prevented by bacitracin, a PDI inhibitor. Our experiments indicated that, during porcine oocyte maturation, PDI undergoes a dramatic reorganization. This characteristic distribution is different from that in the mouse oocyte. Moreover, our study suggested that formation of PDI clusters in the animal pole is a specific characteristic of matured porcine oocytes.
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