Román-Trufero Mónica, Méndez-Gómez Héctor R, Pérez Claudia, Hijikata Atsushi, Fujimura Yu-ichi, Endo Takaho, Koseki Haruhiko, Vicario-Abejón Carlos, Vidal Miguel
Cell and Developmental Biology, Centro de Investigaciones Biológicas, Instituto Cajal, Consejo Superior de Investigaciones Cientificas, Madrid, Spain.
Stem Cells. 2009 Jul;27(7):1559-70. doi: 10.1002/stem.82.
Cell lineages generated during development and tissue maintenance are derived from self-renewing stem cells by differentiation of their committed progeny. Recent studies suggest that epigenetic mechanisms, and in particular the Polycomb group (PcG) of genes, play important roles in controlling stem cell self-renewal. Here, we address PcG regulation of stem cell self-renewal and differentiation through inactivation of Ring1B, a histone H2A E3 monoubiquitin ligase, in embryonic neural stem cells (NSCs) from the olfactory bulb of a conditional mouse mutant line. We show that neural stem/progenitor cell proliferation in vivo and in neurosphere assays is impaired, lacking Ring1B, and their self-renewal and multipotential abilities, assessed as sphere formation and differentiation from single cells, are severely affected. We also observed unscheduled neuronal, but not glial, differentiation of mutant stem/progenitor cells under proliferating conditions, an alteration enhanced in cells also lacking Ring1A, the Ring1B paralog, some of which turned into morphologically identifiable neurons. mRNA analysis of mutant cells showed upregulation of some neuronal differentiation-related transcription factors and the cell proliferation inhibitor Cdkn1a/p21, as well as downregulation of effectors of the Notch signaling pathway, a known inhibitor of neuronal differentiation of stem/progenitor cells. In addition, differentiation studies of Ring1B-deficient progenitors showed decreased oligodendrocyte formation in vitro and enhanced neurogenesis and reduced gliogenesis in vivo. These data suggest a role for Ring1B in maintenance of the undifferentiated state of embryonic neural stem/progenitor cells. They also suggest that Ring1B may modulate the differentiation potential of NSCs to neurons and glia.
发育和组织维持过程中产生的细胞谱系源自自我更新的干细胞，由其定向子代细胞分化而来。最近的研究表明，表观遗传机制，特别是多梳基因家族（PcG），在控制干细胞自我更新中发挥重要作用。在此，我们通过在条件性小鼠突变体系嗅球的胚胎神经干细胞（NSC）中使组蛋白H2A E3单泛素连接酶Ring1B失活，来研究PcG对干细胞自我更新和分化的调控。我们发现，缺乏Ring1B会损害体内神经干/祖细胞的增殖以及神经球实验中的增殖，并且其自我更新和多能性能力（通过球形成和单细胞分化评估）受到严重影响。我们还观察到，在增殖条件下，突变干/祖细胞会出现异常的神经元分化，但无胶质细胞分化，在同时缺乏Ring1B的旁系同源物Ring1A的细胞中这种改变会增强，其中一些细胞会变成形态上可识别的神经元。对突变细胞的mRNA分析显示，一些与神经元分化相关的转录因子和细胞增殖抑制剂Cdkn1a/p21上调，以及Notch信号通路的效应分子下调，Notch信号通路是已知的干/祖细胞神经元分化抑制剂。此外，对Ring1B缺陷祖细胞的分化研究表明，体外少突胶质细胞形成减少，体内神经发生增强，胶质细胞生成减少。这些数据表明Ring1B在维持胚胎神经干/祖细胞的未分化状态中发挥作用。它们还表明Ring1B可能调节神经干细胞向神经元和胶质细胞的分化潜能。
