Preantral follicle culture and oocyte quality.

The formation of high-quality oocytes depends on complex stage-specific interactions between the germ cell and the somatic compartment involving endocrine, paracrine, and autocrine regulation. Cooperativity in bidirectional signalling and metabolism in response to factors in the microenvironment drive growth, proliferation, cell cycle regulation, spindle formation and the establishment of epigenetic marks in oocytes. This is essential to ensure faithful chromosome segregation and to achieve high oocyte quality, with far-reaching consequences for embryo survival, development and the health of offspring.

Improved cryotolerance and developmental potential of in vitro and in vivo matured mouse oocytes by supplementing with a glutathione donor prior to vitrification.

Study Question: Can supplementation of media with a glutathione (GSH) donor, glutathione ethyl ester (GEE), prior to vitrification protect the mouse oocyte from oxidative damage and critical changes in redox homeostasis, and thereby improve cryotolerance?

Summary Answer: GEE supplementation supported redox regulation, rapid recovery of spindle and chromosome alignment after vitrification/warming and improved preimplantation development of mouse metaphase II (MII) oocytes.

What Is Known Already: Cryopreservation may affect mitochondrial functionality, induce oxidative stress, and thereby affect spindle integrity, chromosome segregation and the quality of mammalian oocytes. GEE is a membrane permeable GSH donor that promoted fertilization and early embryonic development of macaque and bovine oocytes after IVM.

Preovulatory Aging In Vivo and In Vitro Affects Maturation Rates, Abundance of Selected Proteins, Histone Methylation Pattern and Spindle Integrity in Murine Oocytes.

Delayed ovulation and delayed fertilization can lead to reduced developmental competence of the oocyte. In contrast to the consequences of postovulatory aging of the oocyte, hardly anything is known about the molecular processes occurring during oocyte maturation if ovulation is delayed (preovulatory aging). We investigated several aspects of oocyte maturation in two models of preovulatory aging: an in vitro follicle culture and an in vivo mouse model in which ovulation was postponed using the GnRH antagonist cetrorelix.

Postovulatory aging affects dynamics of mRNA, expression and localization of maternal effect proteins, spindle integrity and pericentromeric proteins in mouse oocytes.

Study Question: Is the postovulatory aging-dependent differential decrease of mRNAs and polyadenylation of mRNAs coded by maternal effect genes associated with altered abundance and distribution of maternal effect and RNA-binding proteins (MSY2)?

Summary Answer: Postovulatory aging results in differential reduction in abundance of maternal effect proteins, loss of RNA-binding proteins from specific cytoplasmic domains and critical alterations of pericentromeric proteins without globally affecting protein abundance.

What Is Known Already: Oocyte postovulatory aging is associated with differential alteration in polyadenylation and reduction in abundance of mRNAs coded by selected maternal effect genes. RNA-binding and -processing proteins are involved in storage, polyadenylation and degradation of mRNAs thus regulating stage-specific recruitment of maternal mRNAs, while chromosomal proteins that are stage-specifically expressed at pericentromeres, contribute to control of chromosome segregation and regulation of gene expression in the zygote.

Pre- and postovulatory aging of murine oocytes affect the transcript level and poly(A) tail length of maternal effect genes.

Maternal effect genes code for oocyte proteins that are important for early embryogenesis. Transcription in oocytes does not take place from the onset of meiotic progression until zygotic genome activation. During this period, protein levels are regulated posttranscriptionally, for example by poly(A) tail length.

Chronic exposure to a low concentration of bisphenol A during follicle culture affects the epigenetic status of germinal vesicles and metaphase II oocytes.

Objective: To determine whether exposure to low concentrations of the endocrine disrupting chemical bisphenol A (BPA) during follicle culture and oocyte growth alters the methylation status of differentially methylated regions (DMRs) of imprinted genes and histone posttranslational modification patterns in mammalian oocytes.

Design: Comparative and control study.

Setting: Experimental laboratory.

Elements of transcriptional machinery are compatible among plants and mammals.

In the present work, the objective has been to analyse the compatibility of plant and human transcriptional machinery. The experiments revealed that nuclear import and export are conserved among plants and mammals. Further it has been shown that transactivation of a human promoter occurs by human transcription factor NF-κB in plant cells, demonstrating that the transcriptional machinery is highly conserved in both kingdoms.