MicroRNA mechanisms of Rett Syndrome

 描述（由申请人提供）：Rett综合征（RTT）是一种毁灭性的神经发育障碍，是已知的导致女孩自闭症的主要遗传原因。X连锁基因MECP 2（甲基-CpG结合蛋白2）中的突变占RTT病例的绝大多数。MECP 2的神经生物学对于理解RTT的机制和确定该疾病的治疗方法至关重要。MeCP 2是基因表达的表观遗传调节剂，最近已被证明与microRNA机制显着相互作用;这些相互作用是MeCP 2机制的核心。多条证据表明MeCP 2在大脑发育的连续阶段中发挥作用，包括产前神经发生，出生后连接和功能的发育以及经验依赖性突触可塑性。我们假设MeCP 2的多效性作用在产前发育中通过一组影响神经发生的早期调节的miRNA介导;在出生后发育期间通过一组不同的调节胰岛素样生长因子1（IGF 1）信号传导的miRNA介导;在发育后期到成年期通过第三组影响突触功能和可塑性的miRNA介导。该提案的目标是采用尖端的miRNA方法，结合干细胞，行为，双光子成像和靶向电生理方法，以揭示MeCP 2相关miRNA在不同发育阶段的功能。在目标1中，我们将使用等基因人类RTT模型细胞系（目标1a），3-D脑类器官（目标1b）和小鼠模型（目标1c）研究MeCP 2和下游miRNA介导的通路在产前神经发生中的作用。迄今为止，我们的研究结果表明，miR-199和-214在产前神经发生的异常调节中是MeCP 2缺乏的结果;我们将分析这些miRNA下游的功能机制和分子途径。在目标2中，我们将确定出生后MeCP 2调节的miRNA对IGF 1信号传导的影响，以及它们在RTT治疗中的潜在作用。我们将在Mecp 2缺陷小鼠中检测LIN 28 a和BDNF下游的let-7家族miRNAs的调节，以及它们调节IGF 1表达的能力（目的2a）。我们将研究使用β 2肾上腺素能受体激动剂克仑特罗使分子改变水平正常化是否可以积极影响Mecp 2缺陷小鼠的存活率和一系列表型（目的2b），沿着克仑特罗和IGF 1之间的协同相互作用作为RTT的有效机制为基础的组合治疗（目的2c）。在目标3中，我们将研究MeCP 2和晚期表达的miRNA如miR-132在调节经验依赖性皮质可塑性中的作用。我们将确定恢复Mecp 2突变小鼠视皮层中miR-132的表达是否可以恢复正常的眼优势可塑性的年龄依赖性成熟（目的3a）。我们还将研究IGF 1（以及随后的克伦特罗和克伦特罗与IGF 1的组合）是否上调miR-132表达，并通过其下游机制影响可塑性（目的3b）。

 DESCRIPTION (provided by applicant): Rett Syndrome (RTT) is a devastating neurodevelopmental disorder and the leading known genetic cause of autism in girls. Mutations in the X-linked gene MECP2 (methyl-CpG binding protein 2) account for the vast majority of RTT cases. The neurobiology of MECP2 is fundamental to understanding the mechanisms of RTT and identifying therapeutics for the disorder. MeCP2 is an epigenetic modulator of gene expression that has recently been shown to interact significantly with microRNA machinery; these interactions are at the core of MeCP2 mechanisms. Multiple lines of evidence point to a role for MeCP2 in successive stages of brain development, including prenatal neurogenesis, postnatal development of connections and function, and experience-dependent synaptic plasticity. We hypothesize that the pleiotropic effects of MeCP2 are mediated in prenatal development via a set of early regulated miRNAs that influence neurogenesis; during postnatal development through a different set of miRNAs that regulate Insulin-like growth factor 1 (IGF1) signaling; and in late development into adulthood via a third set of miRNAs that influence synaptic function and plasticity. The goal of this proposal is to employ cutting-edge miRNA methodologies, in combination with stem cell, behavioral, two-photon imaging, and targeted electrophysiological approaches, to reveal the function of MeCP2-related miRNAs at different developmental stages. In aim 1, we will examine the role of MeCP2 and downstream miRNA-mediated pathways in prenatal neurogenesis, using isogenic human RTT model cell lines (aim 1a), 3-D cerebral organoids (aim 1b), and mouse models (aim 1c). Our findings to date implicate miR-199 and -214 in the aberrant regulation of prenatal neurogenesis as a result of MeCP2 deficiency; we will analyze the functional mechanisms and molecular pathways downstream of these miRNAs. In aim 2, we will determine the influence of postnatal MeCP2-regulated miRNAs on IGF1 signaling, and their potential role in RTT therapeutics. We will examine the regulation of LIN28a and the let-7 family of miRNAs downstream of BDNF, and their ability to regulate IGF1 expression, in Mecp2 deficient mice (aim 2a). We will investigate whether normalizing the levels of molecular alterations using the ß2 adrenergic receptor agonist clenbuterol can positively impact survival and a range of phenotypes in Mecp2 deficient mice (aim 2b), along with synergistic interactions between clenbuterol and IGF1 as a potent mechanism-based combination therapeutic for RTT (aim 2c). In aim 3, we will examine the role of MeCP2 and late-expressed miRNAs such as miR-132 in regulating experience-dependent cortical plasticity. We will determine whether restoring expression of miR-132 in the visual cortex of Mecp2 mutant mice can restore normal age-dependent maturation of ocular dominance plasticity (aim 3a). We will also examine whether IGF1 (and subsequently, clenbuterol and the combination of clenbuterol and IGF1) upregulates miR-132 expression, and can act through its downstream mechanisms to influence plasticity (aim 3b).