Rab3A, Rab27A, and Rab35 regulate different events during mouse oocyte meiotic maturation and activation.

Rab family members play important roles in membrane trafficking, cell growth, and differentiation. Almost all components of the cell endomembrane system, the nucleus, and the plasma membrane are closely related to RAB proteins. In this study, we investigated the distribution and functions of three members of the Rab family, Rab3A, Rab27A, and Rab35, in mouse oocyte meiotic maturation and activation. The three Rab family members showed different localization patterns in oocytes. Microinjection of siRNA, antibody injection, or inhibitor treatment showed that (1) Rab3A regulates peripheral spindle and cortical granule (CG) migration, polarity establishment, and asymmetric division; (2) Rab27A regulates CG exocytosis following MII-stage oocyte activation; and (3) Rab35 plays an important role in spindle organization and morphology maintenance, and thus meiotic nuclear maturation. These results show that Rab proteins play important roles in mouse oocyte meiotic maturation and activation and that different members exert different distinct functions.

Survivin is essential for fertile egg production and female fertility in mice.

Survivin is the smallest member of the inhibitor of apoptosis protein (IAP) family and acts as a bifunctional protein involved in mitosis regulation and apoptosis inhibition. To identify the physiological role of Survivin in female reproduction, we selectively disrupted Survivin expression in oocytes and granulosa cells (GCs), two major cell types in the ovary, by two different Cre-Loxp conditional knockout systems, and found that both led to defective female fertility. Survivin deletion in oocytes did not affect oocyte growth, viability and ovulation, but caused tetraploid egg production and thus female infertility. Further exploration revealed that Survivin was essential for regulating proper meiotic spindle organization, spindle assembly checkpoint activity, timely metaphase-to-anaphase transition and cytokinesis. Mutant mice with Survivin depleted in GCs showed reduced ovulation and subfertility, caused by defective follicular growth, increased follicular atresia and impaired luteinization. These findings suggest that Survivin has an important role in regulating folliculogenesis and oogenesis in the adult mouse ovary.

Trichostatin A and nuclear reprogramming of cloned rabbit embryos.

To investigate the influence of histone deacetylases on nuclear reprogramming after nuclear transfer, we treated the cloned embryos with a histone deacetylase inhibitor, Trichostatin A (TSA). In the present study, global changes in acetylation of histone H3-lysine 14, histone H4-lysine 12, and histone H4-lysine 5 were studied in rabbit in vivo fertilized embryos, somatic cell nuclear transfer (SCNT) embryos, and TSA-treated SCNT embryos. From the pronuclear to the morula stage, the deacetylation-reacetylation changes in acetylation of histone H3-lysine 14 and histone H4-lysine 12 occurred in both fertilized embryos and TSA-treated cloned embryos; however, the distribution pattern in untreated cloned embryos failed to display such changes. More interesting, the signal of acetylation of histone H4-lysine 12 in cloned embryos was detected in both the inner cell mass and the trophectoderm, whereas TSA-treated cloned embryos showed the same staining pattern as fertilized embryos and the staining was limited to the inner cell mass. The histone acetylation pattern of TSA-treated SCNT embryos appeared to be more similar to that of normal embryos, indicating that TSA could improve nuclear reprogramming after nuclear transfer.