Long exposure to mature ooplasm can alter DNA methylation at imprinted loci in non-growing oocytes but not in prospermatogonia.
Long exposure to mature ooplasm can alter DNA methylation at imprinted loci in non-growing oocytes but not in prospermatogonia.
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DOI：
10.1530/rep-13-0359
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发表时间：
2014-01
期刊：
影响因子：
--
通讯作者：
Kono T
中科院分区：
文献类型：
--
作者：
Obata Y;Wakai T;Hara S;Kono T
在精子发生和卵子发生过程中建立的DNA甲基化印记对配子的功能至关重要。然而，配子特异性印记的机制尚不清楚。在这项研究中，我们研究了来自新生小鼠的雄性和雌性配子是否具有表观遗传可塑性，以及DNA甲基化印记是否受到配子细胞核周围生态位的影响。当具有精子特异性DNA甲基化印记的泌乳细胞与去核的完全成熟的卵母细胞融合并暴露在卵浆中5-6天时，重建的卵母细胞的DNA甲基化状态与分析的所有印迹区域的泌乳细胞保持相同。这些结果表明，早孕细胞的印迹状态是稳定的，早孕细胞的表观基因组丧失了性可塑性。相反，当缺乏卵细胞特异性DNA甲基化印记的未生长卵母细胞与去核的完全成熟卵母细胞融合后，重建的卵母细胞培养5-6天后，Igf2r、kcnq10t1和H19/Igf2差异甲基化区（DMRs）被甲基化。来自5日龄小鼠的卵母细胞中完全没有甲基化印记，H19/Igf2 DMR通常仅在精子发生时甲基化。这些发现表明，在未生长的卵母细胞细胞核中，染色质构象发生改变，并在一些DMR中允许DNA甲基转移酶进入，并且在长期暴露于成熟的卵浆后，H19/Igf2 DMR中维持非甲基化状态的机制丧失。
DNA methylation imprints that are established in spermatogenesis and oogenesis are essential for functional gametes. However, the mechanisms underlying gamete-specific imprinting remain unclear. In this study, we investigated whether male and female gametes derived from newborn mice are epigenetically plastic and whether DNA methylation imprints are influenced by the niche surrounding the nuclei of the gametes. When prospermatogonia possessing sperm-specific DNA methylation imprints were fused with enucleated fully grown oocytes and exposed to the ooplasm for 5–6 days, the DNA methylation status of the reconstituted oocytes remained identical to that of prospermatogonia for all the imprinted regions analysed. These results suggest that the imprinting status of prospermatogonia is stable and that the epigenome of prospermatogonia loses sexual plasticity. By contrast, when non-growing oocytes lacking oocyte-specific DNA methylation imprints were fused with enucleated fully grown oocytes and the reconstituted oocytes were then cultured for 5–6 days, the Igf2r, Kcnq1ot1 and, unexpectedly, H19/Igf2 differentially methylated regions (DMRs) were methylated. Methylation imprints were entirely absent in oocytes derived from 5-day-old mice, and H19/Igf2 DMR is usually methylated only in spermatogenesis. These findings indicate that in the nuclei of non-growing oocytes the chromatin conformation changes and becomes permissive to DNA methyltransferases in some DMRs and that mechanisms for maintaining non-methylated status at the H19/Igf2 DMR are lost upon long exposure to mature ooplasm.