The Role of Astrocyte BMP Signaling in Fragile X Syndrome

项目摘要/摘要 本项目旨在探讨星形胶质细胞骨形态发生蛋白(BMP)信号在骨质疏松症发病机制中的作用。 脆性X综合征(FXS)。FXS是最常见的智力残疾(ID)和自闭症的遗传形式 谱系障碍(ASD)。FXS是由FMR1基因启动子引导的三核苷酸重复扩增引起的 到转录沉默，FXS最常用Fmr1基因敲除(KO)小鼠建模。虽然 研究表明，Fmr1功能丧失的影响有几条途径，其中最有针对性的 治疗在临床试验中失败了，FXS主要是根据症状进行治疗。大多数人 对FXS的研究主要集中在神经元内部的内在变化。然而，对FXS的新研究表明 星形胶质细胞，特别是通过星形胶质细胞分泌的因子。用星形胶质细胞培养的野生型(WT)神经元 来自Fmr1KO小鼠的星形胶质细胞条件培养液(ACM)显示出发育迟缓的轴突生长，并概括了 在Fmr1KO小鼠和人FXS患者体内观察到的未成熟树突棘表型，提供了直接的 星形胶质细胞分泌因子在FXS中起因果作用的证据。FXS星形胶质细胞的初步数据分析 转录和蛋白质分泌鉴定出四种蛋白质，它们都在mRNA中过度表达和过度分泌，一个 其中Bmp6。此外，WT星形胶质细胞中BMP信号的激活产生了超过三分之一的蛋白质 FXS星形胶质细胞分泌的变化，而BMP信号在FXS星形胶质细胞中的缺失使突起消失 超过了增长赤字。这项提议的目标是验证星形胶质细胞中BMP信号是上游信号的假设 目的是研究体内神经发育FXS缺陷的情况，并确定介导这一效应的星形胶质细胞分泌的蛋白质。 一种基因和病毒相结合的方法选择性敲除星形胶质细胞中的Bmpr2或Smad4将被用于 星形胶质细胞BMP信号下调能否挽救体内树突状细胞FXS异常 脊椎、可塑性和行为。一种星形胶质细胞特异性体内蛋白质组学方法 在体外对特定蛋白质的研究将确定BMP信号下游导致FXS缺陷的蛋白质。这些 实验将确定星形胶质细胞中的BMP信号是否在体内介导FXS缺陷并阐明 它发生的机制，从而提供了对FXS以前被低估的一个方面的新见解 病理生理学。这项拟议的研究将在索尔克生物研究所的艾伦实验室进行 这是一个协作研究环境，提供获得所有必要设备和培训的途径。 通过分子神经生物学的理论和实践培训，与不同的支持者合作 研究和临床背景，以及一个致力于导师的研究团队，建议进行研究 培训计划将在研究方面提供严格的指导，并为未来的职业生涯奠定基础 独立的医生兼科学家。

Project Summary/Abstract This project addresses the role of astrocyte bone morphogenetic protein (BMP) signaling in the pathogenesis of Fragile X Syndrome (FXS). FXS is the most common inherited form of intellectual disability (ID) and autism spectrum disorder (ASD). FXS is caused by trinucleotide repeat expansion in the FMR1 gene promoter leading to transcriptional silencing, and FXS is most often modeled with the Fmr1 knockout (KO) mouse. Although research has implicated several pathways mediating the effects of the Fmr1 loss of function, most targeted treatments have failed in clinical trials, and FXS is predominantly treated by symptom only. The majority of research in FXS has focused on intrinsic changes within neurons. However, emerging research in FXS implicates astrocytes, specifically through astrocyte-secreted factors. Wild-type (WT) neurons cultured with astrocytes or astrocyte-conditioned media (ACM) from Fmr1 KO mice exhibit stunted neurite outgrowth and recapitulate the immature dendritic spine phenotype observed in vivo in Fmr1 KO mice and human FXS patients, providing direct evidence for a causal role of astrocyte-secreted factors in FXS. Preliminary data profiling FXS astrocyte transcription and protein secretion identified four proteins both overexpressed in mRNA and oversecreted, one of which is BMP6. Furthermore, activation of BMP signaling in WT astrocytes generates over a third of the protein secretion changes of FXS astrocytes, while abrogation of BMP signaling in FXS astrocytes abolishes neurite outgrowth deficits. The goal of this proposal is to test the hypothesis that BMP signaling in astrocytes is upstream of neurodevelopmental FXS deficits in vivo and to identify the astrocyte-secreted proteins that mediate this effect. A combined genetic and viral approach to selective knock out Bmpr2 or Smad4 in astrocytes will be used to assess whether downregulation of astrocyte BMP signaling can rescue in vivo FXS abnormalities in dendritic spines, plasticity, and behavior. An astrocyte-specific in vivo proteomic approach combined with characterization of specific proteins in vitro will identify proteins downstream of BMP signaling responsible for FXS deficits. These experiments will determine if BMP signaling in astrocytes mediates FXS deficits in vivo and elucidate mechanisms by which it occurs, thereby providing new insight into a previously underappreciated aspect of FXS pathophysiology. The proposed research will take place in the Allen Laboratory at the Salk Institute for Biological Studies, a collaborative research environment that provides access to all necessary equipment and training. Through theoretical and practical training in molecular neurobiology, collaboration with supporters of diverse research and clinical backgrounds, and a research team committed to mentorship, the proposed research training plan will enable rigorous instruction in research and lay the foundation for a future career as an independent physician-scientist.