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NSN to SN transition in mouse oocytes: nuclear architecture dynamics and epigenetic landscape

Abstract : During this final step of oogenesis, the oocyte nucleus is subject to large-scale modifications that correlate with transcriptional silencing. While oocytes with dense chromatin around the nucleolus (SN) are silent, oocytes with uncondensed chromatin (NSN) are transcriptionally active. It is believed that epigenetic mechanisms that participate to gene expression regulation could play a role in this event. In this context, we examined the behaviour of heterochromatin and related histone modifications during the NSN to SN transition by immuno-stainings. We also studied with 3D-FISH (Fluorescent In Situ Hybridization on 3D-preserved nuclei) the distribution of centromeric, pericentromeric and ribosomal (rDNA) sequences in relation to the nucleolus (also called nucleolus like body, NLB). We observed that in NSN-type oocytes pericentromeric heterochromatin is aggregated within chromocenters. In SN-type oocytes, pericentromeric heterochromatin and centromeres form a discontinuous ring around the NLB. rDNA sequences, which initially present a pearl necklace structure, gather together in seven highly condensed foci at the NLB periphery. H3K9me3 and H4K20me3 heterochromatin marks clearly label chromocenters whereas H3K4me3 and H4K5ac are totally excluded from heterochromatin regions, even in the very compact SN-nuclei. Remarkably, H3K27me3 displays an intermediate behavior. It appears that GV oocytes nuclei exhibit a specific epigenetic landscape. Histones modifications, related to both active and repressive chromatin structures, seem to follow the large-scale chromatin movements that occur during the NSN to SN transition. We also demonstrate that, while heterochromatin regions re-localize around the NLB, rDNA sequences adopt a highly compact structure in SN-type oocytes.
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https://hal.inrae.fr/hal-02747568
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Submitted on : Wednesday, June 3, 2020 - 12:04:39 PM
Last modification on : Thursday, August 5, 2021 - 3:53:20 AM

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  • HAL Id : hal-02747568, version 1
  • PRODINRA : 267755

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Amélie Bonnet-Garnier, Prisca Feuerstein, Martine Chebrout, Renaud Fleurot, Tiphaine Aguirre-Lavin, et al.. NSN to SN transition in mouse oocytes: nuclear architecture dynamics and epigenetic landscape. Dynamic Organization of Nuclear Function Meeting, Cold Spring Harbor Laboratory. USA., Sep 2012, New York, United States. 178 p. ⟨hal-02747568⟩

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