Role of small RNAs in Neurogenesis

描述(申请人提供)：神经发生被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，在多个分子水平上进行调节。破译这些调控机制是了解哺乳动物出生后大脑的发育和可塑性以及实现神经干细胞/祖细胞(NSCs)治疗潜力的一步。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发挥重要作用。甲基-CpG结合蛋白，包括MBD1和MeCP2，是表观遗传调控的核心角色，可以将DNA甲基化转化为基因表达的变化。据报道，在散发性人类癌症中存在MBD1缺陷，这与其在细胞生长控制中的作用是一致的。尽管MBD1的表达模式无处不在，但我们发现，MBD1缺乏在小鼠出生后很大程度上会导致脑相关表型，包括成年神经发生受损和相关行为缺陷，如海马体依赖学习缺陷以及焦虑和抑郁易感性。最近，在自闭症患者的一个亚群中发现了MBD1突变，并与更严重的表型相关。然而，MBD1在出生后神经元发育中的确切作用及其作用的分子途径尚不完全清楚。在过去的三年资助期间，我们发现MBD1调控着许多miRNAs的表达，其中一些miRNAs在神经发生中显示出重要的调控作用。例如，miR-184通过抑制Notch信号调节因子Numblike(NBL)的表达来促进成年NSCs的增殖和抑制其分化。这个监管网络的完整图景仍然缺乏。除了在神经干细胞增殖和神经元分化中的作用外，我们还发现MBD1在新生神经元的成熟过程中也有重要的作用。事实上，一些受MBD1调控的miRNAs与神经元成熟有关。综上所述，这些突破性的发现是这一提议的基础，该提议旨在更好地理解控制出生后神经发生的多个阶段的表观遗传学机制。我们将检验这一假设，即MBD1对miRNAs及其后续下游靶点的调控对出生后神经发生至关重要。因此，我们建议确定MBD1调控的miRNAs如何调控aNSCs的增殖和分化(Aim 1)，确定MBD1调控的miRNAs是否以及如何调控新神经元的成熟(Aim 2)，并探索MBD1调控小RNAs的机制(Aim 3)。这些结果将为控制出生后神经发生的表观遗传机制提供新的见解。 公共卫生相关性：使用我们独特的模型系统表征MBD1及其调控的非编码小RNA在出生后神经发生中的作用，将为深入了解哺乳动物神经元发育和神经可塑性背后的新表观遗传机制提供见解，这可能对理解和治疗自闭症、抑郁症和学习障碍等精神障碍具有重要意义。

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. PUBLIC HEALTH RELEVANCE: Characterizing the role of MBD1 and its regulated noncoding small RNAs in the postnatal neurogenesis using our unique model system will provide insights into the novel epigenetic mechanisms underlying mammalian neuronal development and neuroplasticity, which could have significant implication in understanding and treating mental disorders such as autism, depression, and learning deficits.