Genome organization and epigenetic marks in mouse germinal vesicle oocytes
Genome organization and epigenetic marks in mouse germinal vesicle oocytes
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DOI：
10.1387/ijdb.120149ab
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发表时间：
2012-01-01
影响因子：
0.7
通讯作者：
Beaujean, Nathalie
中科院分区：
文献类型：
--
作者：
Bonnet-Garnier, Amelie;Feuerstein, Prisca;Beaujean, Nathalie
在卵子发生的最后一步，卵母细胞细胞核受到与转录沉默相关的大规模修饰。核仁周围染色质致密的卵母细胞沉默（SN，包围核仁），染色质不凝聚的卵母细胞转录活跃（NSN，非包围核仁）。据信，参与基因表达调控的表观遗传机制可能在这一事件中发挥作用。在这种情况下，我们通过免疫染色检测了异染色质和相关组蛋白修饰在NSN向SN转变过程中的行为。利用三维保存细胞核的荧光原位杂交技术（3D-FISH），我们还研究了与核仁（也称为核仁样体，NLB）相关的着丝粒、周中心粒和核糖体（rDNA）序列的分布。我们观察到，在nsn型卵母细胞中，染色质聚集在染色质中心内。在sn型卵母细胞中，着丝粒周围的异染色质和着丝粒形成一个不连续的环。rDNA序列最初呈珍珠项链结构，聚集在NLB外围的7个高度浓缩的病灶中。H3K9me3和H4K20me3异染色质标记了明显的标记色中心，而H3K4me3和H4K5ac完全排除在异染色质区域之外，即使在非常致密的sn核中也是如此。值得注意的是，H3K27me3表现出一种中间行为。GV卵母细胞细胞核似乎表现出一种特殊的表观遗传景观。组蛋白修饰与活性和抑制性染色质结构相关，似乎遵循NSN向SN转变过程中发生的大规模染色质运动。我们还证明，当异染色质区域在NLB周围重新定位时，rDNA序列在sn型卵母细胞中采用高度紧凑的结构。
During the 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 are silent (SN, surrounded nucleolus), oocytes with uncondensed chromatin (NSN, non-surrounded nucleolus) are transcriptionally active. It is believed that epigenetic mechanisms that participate in 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 immunostaining. Using fluorescent in situ hybridization on three dimensional-preserved nuclei (3D-FISH), we also studied the distribution of centromeric, pericentromeric and ribosomal (rDNA) sequences in relation to the nucleolus (also called the 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 oocyte nuclei exhibit a specific epigenetic landscape. Histone 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.