Role of small RNAs in Neurogenesis

描述（由申请人提供）：神经发生定义为新神经元的产生和成熟。出生后的神经发生，被认为是神经可塑性和记忆的重要过程，在多个分子水平上受到调节。破译这些调控机制代表了理解哺乳动物出生后大脑发育和可塑性的一步，并实现神经干/祖细胞（NSC）的治疗潜力。表观遗传机制，包括DNA甲基化和组蛋白修饰，已知在干细胞增殖和分化的调节中起重要作用。甲基CpG结合蛋白，包括MBD 1和MeCP 2，是表观遗传调控的核心参与者，可以将DNA甲基化转化为基因表达变化。在散发性人类癌症中已经报道了MBD 1缺陷，这与其在细胞生长控制中的作用一致。尽管其普遍存在的表达模式，我们发现，MBD 1缺乏症在小鼠中主要导致出生后时期的脑相关表型，包括成年神经发生受损和相关的行为缺陷，如有缺陷的大脑依赖性学习和对焦虑和抑郁的易感性。最近，MBD 1突变在自闭症患者的一个子集中被发现，并与更严重的表型相关。然而，MBD 1在出生后神经元发育中的确切作用以及介导其作用的分子途径尚不完全清楚。在过去三年的资助期间，我们发现MBD 1调节许多miRNAs的表达，其中一些miRNAs在神经发生中表现出重要的调节作用。例如，miR-184通过抑制Numblike（Nbl）（Notch信号传导的调节剂）的表达来促进成体NSC的增殖并抑制其分化。这一监管网络的全貌仍然缺乏。除了在NSC增殖和神经元分化中的作用外，我们发现MBD 1在新神经元的成熟中也具有重要作用。事实上，一些MBD 1调节的miRNA与神经元成熟有关。总之，这些突破性的发现作为这个建议的基础，其目的是为了更好地了解控制多个阶段的出生后神经发生的表观遗传机制。我们将检验MBD 1对miRNAs及其下游靶点的调节对出生后神经发生至关重要的假设。因此，我们建议确定MBD 1调节的miRNA如何管理aNSCs的增殖和分化（Aim 1），以确定MBD 1调节的miRNA是否以及如何调节新神经元的成熟（Aim 2），并探索MBD 1调节小RNA的潜在机制（Aim 3）。这些结果将为研究生后神经发生的表观遗传机制提供新的见解。

DESCRIPTION (provided by applicant): Neurogenesis is defined as generation and maturation of new neurons. Postnatal neurogenesis, a process considered important for neuroplasticity and memory, is regulated at multiple molecular levels. Deciphering these regulatory mechanisms represents a step towards understanding the development and plasticity of postnatal mammalian brains, and realizing the therapeutic potential of neural stem/progenitor cells (NSCs). Epigenetic mechanisms, including DNA methylation and histone modification, are known to play significant roles in the modulation of stem cell proliferation and differentiation. Methyl-CpG binding proteins, including MBD1 and MeCP2, are central players in epigenetic regulation, and can translate DNA methylation into gene expression changes. MBD1 deficiency has been reported in sporadic human cancers, consistent with its role in cellular growth control. Despite its ubiquitous expression pattern, we found that MBD1 deficiency in mice results largely in brain-associated phenotypes during the postnatal period, including impaired adult neurogenesis and related behavioral deficits such as defective hippocampus-dependent learning and susceptibility to anxiety and depression. Recently, MBD1 mutations were found in a subset of autistic patients and were correlated with more severe phenotypes. However, the precise role of MBD1 in postnatal neuronal development and molecular pathway mediating its effect is not fully clear. During the past three-year funding period, we have discovered that MBD1 regulates the expression of a number of miRNAs and some of these miRNAs exhibit an important regulatory role in neurogenesis. For example, miR-184 promotes proliferation and represses differentiation of adult NSCs by repressing the expression of Numblike (Nbl), a regulator of Notch signaling. The complete picture of this regulatory network is still lacking. In addition to its role in NSC proliferation and neuronal differentiation, we discovered that MBD1 also had important roles in maturation of new neurons. Indeed, some of MBD1-regulated miRNAs have been implicated in neuronal maturation. Taken together, these breakthrough discoveries serve as the basis of this proposal which is aimed towards a better understanding of the epigenetic mechanisms controlling multiple stages of postnatal neurogenesis. We will test the hypothesis that MBD1 regulation of miRNAs and their subsequent downstream targets is critical for postnatal neurogenesis. Therefore we propose to determine how MBD1-regulated miRNAs govern the proliferation and differentiation of aNSCs (Aim 1), to determine whether and how MBD1-regulated miRNAs modulate the maturation of new neurons (Aim 2), and to explore the mechanism underlying MBD1 regulation of small RNAs (Aim 3). The results will provide novel insights into the epigenetic mechanisms governing postnatal neurogenesis.