Histone exchange activity and its correlation with histone acetylation status in porcine oocytes.
ABSTRACT In mammalian oocytes, histone H3 and histone H4 (H4) in the chromatin are highly acetylated at the germinal vesicle (GV) stage, and become globally deacetylated after GV breakdown (GVBD). Although nuclear core histones can be exchanged by cytoplasmic free histones in somatic cells, it remains unknown whether this is also the case in mammalian oocytes. In this study, we examined the histone exchange activity in maturing porcine oocytes before and after GVBD, and investigated the correlations between this activity and both the acetylation profile of the H4 N-terminal tail and the global histone acetylation level in the chromatin. We injected Flag-tagged H4 (H4-Flag) mRNA into GV oocytes, and found that the Flag signal was localized to the chromatin. We next injected mRNAs of mutated H4-Flag, which lack all acetylation sites and the whole N-terminal tail, and found that the H4 N-terminal tail and its modification were not necessary for histone incorporation into chromatin. Despite the lack of acetylation sites, the mutated H4-Flag mRNA injection did not decrease the acetylation level on the chromatin, indicating that the histone exchange occurs partially in the GV chromatin. In contrast to GV oocytes, the Flag signal was not detected on the chromatin after the injection of H4-Flag protein into the second meiotic metaphase oocytes. These results suggest that histone exchange activity changes during meiotic maturation in porcine oocytes, and that the acetylation profile of the H4 N-terminal tail has no effect on histone incorporation into chromatin and does not affect the global level of histone acetylation in it.
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ABSTRACT: In some insect species, two sites of juvenile hormone (JH) synthesis have been reported: the very well documented corpora allata that secrete JH for "general use", and the reproductive system, in particular the male accessory glands, in which the function of the sometimes huge amounts of JH (e.g. in Hyalophora cecropia) remains to be clarified. A recent finding in Schistocerca gregaria, namely that suppression of the ecdysteroid peak preceding a molt by RNAi of the Halloween genes spook, phantom and shade does not impede normal molting, challenges the (never experimentally proven) classical concept that such a peak is causally linked to a molt. Recent developments in epigenetic control of gene expression in both the honey bee and in locusts suggest that, in addition to the classical scheme of hormone-receptor (membrane- and/or nuclear) mode of action, there may be a third way. Upon combining these and other orphan data that do not fit in the commonly accepted textbook schemes, we here advance the working hypothesis that both JH and ecdysone might be important but overlooked players in epigenetic control of gene expression, in particular at extreme concentrations (peak values or total absence). In this review, we put forward how epi-endocrinology can complement classical arthropod endocrinology.General and Comparative Endocrinology 02/2013; 188. DOI:10.1016/j.ygcen.2013.02.004 · 2.67 Impact Factor
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ABSTRACT: It is well documented that oocytes from small antral follicles are less competent than those derived from large follicles, and we have previously shown that glial cell line-derived neurotrophic factor (GDNF) enhances developmental competence in oocytes from antral follicles. Exactly how GDNF affects this change and if it depends on the stage of oocyte development is currently unknown. The objective of this study was to examine the transcriptomic effects of follicle size and GDNF on the in vitro maturation of porcine oocytes. Microarray analysis uncovered differentially expressed transcripts among in vitro-matured porcine oocytes from different-size antral follicles, in the absence or presence of GDNF. Oocytes isolated from small follicles showed a lower state of maturation than those from large follicles, with several transcripts associated with meiotic arrest. Addition of GDNF to the culture media had effects that depended on the stage of the follicle from which the oocyte was isolated, with those from small follicles showing decreased expression of genes associated with acetyltransferase activity while those from large follicles showed decreased metabolic activity. In summary, our results revealed considerable differences between the transcriptomes of small- and larger-follicle-derived oocytes. Furthermore, GDNF affects the developmental competence of oocytes in follicle-stage dependent manner. Thus improving our understanding of the requirements for successful in vitro maturation of porcine oocytes will inform current reproductive technologies, with implications for the future of animal and human health. Mol. Reprod. Dev. © 2013 Wiley Periodicals, Inc.Molecular Reproduction and Development 03/2014; DOI:10.1002/mrd.22288 · 2.68 Impact Factor