Novel candidate mechanisms of fragile X syndrome

脆性X综合征（FXS）是最常见的遗传性精神发育迟滞形式，由破坏FMR 1基因的突变引起。很大一部分FXS患者具有自闭症谱系障碍（ASD）的特征。由FMR 1编码的蛋白质，脆性X智力低下蛋白（FMRP），结合mRNA并调节其翻译。FMRP靶mRNA在人类神经发育中的身份和功能以及它们如何促进FXS尚不清楚。在我的初步数据中，部分数据构成了我目前正在出版的手稿的基础（Kwan等人，Cell，2012），我表明一氧化氮合酶1（NOS 1）mRNA在发育中的人新皮质中与FMRP结合并受其调节，并且NOS 1蛋白在FXS的胎儿病例中丢失。因此，NOS 1功能丧失代表了FXS的一个有前途的新候选机制。在这个应用程序中，我建议进一步追求这一令人兴奋的研究路线。在目标1中，我将研究NOS 1的缺失如何导致FXS和ASD的病理生理学，FXS通常与ASD共病。具体来说，我将分析：锥体NOS 1在发育过程中的神经生物学作用; NOS 1的遗传贡献，以及在一氧化氮（NO）合成中作用于NOS 1上游的基因，对ASD;以及锥体神经元中NOS 1信号传导的下游事件。对于目标2，我建议确定额外的新的候选机制FXS使用死后人脑组织，并测试其失调FXS使用FXS大脑和神经干细胞。这种多方面的应用预计将在几个领域提供培训，包括人类遗传学，生物化学，人体组织处理，突触分析，神经干细胞培养和高通量测序的新技术。这种额外的培训对我成功过渡到独立至关重要。我在指导阶段的培训进度和我寻找独立职位的过程将由我的共同导师和一个由四名具有不同专业知识的教师组成的委员会监督。拟议的研究对目前研究FXS的方法具有影响，并有可能发现不仅FXS而且ASD的新分子途径。 脆性X综合征是最常见的遗传性精神发育迟滞。我建议研究脆性X综合征的分子基础。这项工作将对脆性X综合征以及自闭症谱系障碍的潜在疗法产生影响。

DESCRIPTION (provided by applicant): Project Summary Fragile X syndrome (FXS), the most common inherited form of mental retardation, result from mutations that disrupt the FMR1 gene. A large proportion of FXS patients have features of autism spectrum disorder (ASD). The protein encoded by FMR1, fragile X mental retardation protein (FMRP), binds mRNAs and regulates their translation. The identity and function of FMRP target mRNAs in human neurodevelopment and how they contribute to FXS are not well understood. In my preliminary data, parts of which formed the basis of my manuscript currently in press (Kwan et al., Cell, 2012), I show that nitric oxide synthase 1 (NOS1) mRNA is bound to and regulated by FMRP in the developing human neocortex and NOS1 protein is lost in fetal cases of FXS. Therefore, NOS1 loss of function represents a promising novel candidate mechanism of FXS. In this application, I propose to further pursue this exciting line of research. In Aim 1, I will examine how loss of NOS1 may contribute to the pathophysiology of FXS and ASD, with which FXS is often comorbid. Specifically, I will analyze: the neurobiological role of pyramidal NOS1 during development; the genetic contribution of NOS1, and genes that act upstream of NOS1 in the synthesis of nitric oxide (NO), to ASD; and the events downstream of NOS1 signaling in pyramidal neurons. For Aim 2, I propose to identify additional novel candidate mechanisms of FXS using postmortem human brain tissue and to test their dysregulation in FXS using FXS brains and neural stem cells. This multifaceted application is expected to provide training in several areas, including novel techniques in human genetics, biochemistry, human tissue processing, synapse analysis, neural stem cell culture, and high-throughput sequencing. This additional training is critical to my successful transition to independence. The progress of my training during the mentored phase and my search for an independent position will be overseen by my co-mentors and a committee of four additional faculty members with diverse expertise. The proposed studies have implications for current approaches to study of FXS and have the potential to uncover novel molecular pathways of not only FXS but also ASD. PUBLIC HEALTH RELEVANCE: Project Narrative Fragile X syndrome is the most common inherited form of mental retardation. I propose to study the molecular underpinnings of fragile X syndrome. This work will have implications for potential therapies for fragile X syndrome, as well as autism spectrum disorder.