近日,，哈爾濱醫(yī)科大學(xué)基礎(chǔ)醫(yī)學(xué)院組胚教研室科研人員最新研究發(fā)現(xiàn)，體細(xì)胞中rDNA（核糖體DNA）的活性與克隆胚胎早期胚胎發(fā)育過程中的核仁活性和功能之間聯(lián)系密切,，這一發(fā)現(xiàn)為重編程機(jī)理的研究提供了新的視角和切入點(diǎn)。相關(guān)論文在線發(fā)表于《生物化學(xué)期刊》（Journal of Biological Chemistry）,。
細(xì)胞的生長和增殖依賴足夠的核糖體以維持蛋白質(zhì)合成,。目前體細(xì)胞克隆效率很低，重編程過程能否開啟沉默的rDNA轉(zhuǎn)錄,，從而產(chǎn)生充足的rRNA以保障核糖體和蛋白的合成,，可能與開啟發(fā)育關(guān)鍵基因的轉(zhuǎn)錄同樣重要。
哈醫(yī)大基礎(chǔ)醫(yī)學(xué)院組胚教研室教授雷蕾帶領(lǐng)博士研究生鄭重等人員,，從核糖體基因的表觀修飾出發(fā),，研究分化的體細(xì)胞中，rDNA的活性對克隆胚胎早期發(fā)育過程中rDNA重新激活的影響,。
他們的實(shí)驗(yàn)表明,，小鼠胚胎干細(xì)胞、顆粒細(xì)胞和成纖維細(xì)胞的rDNA甲基化水平分別為6.67%,、13.59%和22.57%，呈遞增趨勢,。與之對應(yīng),，銀染顯示活性核仁組織區(qū)（NORs）數(shù)目分別為7.66、6.45和4.70,，呈遞減趨勢,，且熒光實(shí)時(shí)定量PCR顯示胚胎干細(xì)胞的rRNA合成和加工水平要高于另兩種細(xì)胞。
專家認(rèn)為,，這項(xiàng)研究首次證明了體細(xì)胞中rDNA的活性與克隆胚胎早期胚胎發(fā)育過程中的核仁活性和功能之間的密切聯(lián)系,，為重編程機(jī)理的研究提供了新的視角和切入點(diǎn)。同時(shí),，由于rDNA的活性與細(xì)胞增殖,、衰老,、分化等密切相關(guān)，這一成果也為深入探討延緩細(xì)胞衰老,、核糖體病變及腫瘤的發(fā)生與治療奠定了基礎(chǔ),。(生物谷Bioon.com)
doi:10.1074/jbc.M112.355099
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rRNA genes are not fully activated in mouse somatic cell nuclear transfer embryos
Zhong Zheng1, Jia-lin Jia1, Gerelchimeg Bou2, Li-Li Hu1, Zhen-Dong Wang1, Xing-Hui Shen1, Zhi-Yan Shan1, Jing-Ling Shen1, Zhong-Hua Liu2 and Lei Lei
The well-known and most important function of nucleoli is ribosome biogenesis. However, the nucleolus showed delayed development and malfunction in somatic cell nuclear transfer (NT) embryos. Previous studies indicated that nearly half rRNA genes (rDNA) in somatic cells were inactive and not transcribed. We compared the rDNA methylation level, active nucleolar organizer regions (NORs) numbers, nucleolar proteins (upstream binding factor/UBF, nucleophosmin/B23) distribution and nucleolar related gene expression in three different donor cells and NT embryos. The results showed embryonic stem cells (ESCs) had the most active NORs and lowest rDNA methylation level (7.66 and 6.76%) while mouse embryonic fibroblasts (MEFs) were the opposite (4.70 and 22.57%). After the donor cells were injected into enucleated MII oocytes, cumulus cells (CCs) and MEFs nuclei lost B23 and UBF signals in 20min, while in ESC-NT embryos, B23 and UBF signals could still be detected at 60min post NT. The embryos derived from ESCs, CCs, and MEFs showed the same trend in active NORs numbers (7.19 vs. 6.68 vs. 5.77, P<0.05) and rDNA methylation level (6.36% vs. 9.67% vs. 15.52%) at 4-cell stage as that in donor cells. However, the MEF-NT embryos displayed low rRNA synthesis/processing potential at morula stage and had an obvious decrease in blastocyst developmental rate. The results presented clear evidences that the rDNA reprogramming efficiency in NT embryos was determined by the rDNA activity in donor cells from which they derived.
