Mediator subunit Med12 contributes to the maintenance of neural stem cell identity.
Mediator subunit Med12 contributes to the maintenance of neural stem cell identity.
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DOI：
10.1186/s12861-016-0114-0
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发表时间：
2016-05-17
影响因子：
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通讯作者：
Boyer TG
中科院分区：
文献类型：
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作者：
Kim NH;Livi CB;Yew PR;Boyer TG
RNA聚合酶II转录调节亚基MED12广泛参与脊椎动物脑发育，人类MED12基因变异与X连锁智力残疾和神经精神障碍有关。虽然先前的研究已经开始阐述MED12在关键的神经发育途径中的功能贡献，但对MED12在神经系统发育中的功能，包括其调控下的特定生物网络和细胞过程的更完整的描述，仍有待建立。在此，我们试图通过在RNAi介导的MED12缺失后对小鼠胚胎干细胞(ES)来源的NSC进行无偏见的转录组谱分析来阐明MED12对神经干细胞(NSC)生物学的全球贡献。共有240个基因(177个上调，73个下调)在MED12基因敲除的小鼠神经干细胞与对照组NS-5(MNS-5)神经干细胞中差异表达。基因集浓缩分析显示，MED12与“细胞间相互作用”和“细胞周期”网络显著相关，随后的功能研究证实了这些联系。靶向缺失MED12导致NSC黏附增强和细胞黏附基因上调，包括Syndecan 2(Sdc2)。伴随的Sdc2和MED12的缺失逆转了由MED12基因敲除单独触发的增强的细胞黏附，证实MED12通过抑制细胞黏附分子的表达而负向调节NSC的黏附。MED12介导的神经干细胞黏附抑制在体外是一个动态调节的过程，在神经干细胞自我更新过程中被加强，在神经元分化过程中被抑制。因此，MED12的缺失增强了MNS-5神经干细胞在明胶上诱导分化的粘附力和延长了存活时间，这种作用完全被层粘连蛋白上的生长所绕过。另一方面，MNS-5 NSCs中MED12缺失导致G1/S期细胞周期调控因子表达减少，细胞周期受阻于G1/S期，但未见明显的细胞凋亡迹象，导致严重的增殖缺陷。MED12通过抑制和激活分别与细胞黏附和G1/S期细胞周期进程有关的基因表达程序，在功能上对维持神经干细胞的特性做出贡献。因此，MED12可能有助于调控NSC自我更新和分化之间的平衡，对MED12相关的神经发育障碍具有重要意义。本文的在线版本(doi：10.1186/s12861-0160114-0)包含补充材料，授权用户可以使用。
The RNA polymerase II transcriptional Mediator subunit Med12 is broadly implicated in vertebrate brain development, and genetic variation in human MED12 is associated with X-linked intellectual disability and neuropsychiatric disorders. Although prior studies have begun to elaborate the functional contribution of Med12 within key neurodevelopmental pathways, a more complete description of Med12 function in the developing nervous system, including the specific biological networks and cellular processes under its regulatory influence, remains to be established. Herein, we sought to clarify the global contribution of Med12 to neural stem cell (NSC) biology through unbiased transcriptome profiling of mouse embryonic stem (ES) cell-derived NSCs following RNAi-mediated Med12 depletion. A total of 240 genes (177 up, 73 down) were differentially expressed in Med12-knockdown versus control mouse NS-5 (mNS-5) NSCs. Gene set enrichment analysis revealed Med12 to be prominently linked with “cell-to-cell interaction” and “cell cycle” networks, and subsequent functional studies confirmed these associations. Targeted depletion of Med12 led to enhanced NSC adhesion and upregulation of cell adhesion genes, including Syndecan 2 (Sdc2). Concomitant depletion of both Sdc2 and Med12 reversed enhanced cell adhesion triggered by Med12 knockdown alone, confirming that Med12 negatively regulates NSC cell adhesion by suppressing the expression of cell adhesion molecules. Med12-mediated suppression of NSC adhesion is a dynamically regulated process in vitro, enforced in self-renewing NSCs and alleviated during the course of neuronal differentiation. Accordingly, Med12 depletion enhanced adhesion and prolonged survival of mNS-5 NSCs induced to differentiate on gelatin, effects that were bypassed completely by growth on laminin. On the other hand, Med12 depletion in mNS-5 NSCs led to reduced expression of G1/S phase cell cycle regulators and a concordant G1/S phase cell cycle block without evidence of apoptosis, resulting in a severe proliferation defect. Med12 contributes to the maintenance of NSC identity through a functionally bipartite role in suppression and activation of gene expression programs dedicated to cell adhesion and G1/S phase cell cycle progression, respectively. Med12 may thus contribute to the regulatory apparatus that controls the balance between NSC self-renewal and differentiation, with important implications for MED12-linked neurodevelopmental disorders. The online version of this article (doi:10.1186/s12861-016-0114-0) contains supplementary material, which is available to authorized users.