Mechanisms of circuit failure and treatments in patient-derived neurons in autism

描述（由申请人提供）：缺乏用于探索细胞机制的经验证的临床前模型限制了严重自闭症的治疗开发。为了开发新的临床前模型和治疗剂，对患者来源的神经元中的细胞表型和对潜在药剂的细胞应答的严谨研究将是有利的。这项研究的长期目标是阐明严重自闭症病理学的分子机制，这将成为为这些目前治疗选择很少的患者开发创新治疗方法的基础。我们最近发现了一个新的机制，自闭症涉及内体Na+/H+交换（NHEs）。我们现在已经从具有一系列NHE 6突变的患者中产生了诱导多能干细胞系（iPSC）。本申请的目的是阐明NHE 6在人轴突发育中的作用，并测试患者来源的神经元对可随后用作患者治疗的可用的基于机制的药剂的反应。NHE 6调节质子从内体的流出。在我们对人类神经元的初步研究中，NHE 6缺乏导致内体腔的过度酸化以及轴突生长和分支的缺陷。这种机制是偶然的，因为有一些众所周知的FDA批准的药物，目标内体pH值。我们的中心假设是，NHE 6的缺乏抑制轴突生长和分支，由于减少极化膜添加。这项研究的基本原理是，它构成了发展新的治疗方法的第一个关键步骤， 患有严重自闭症和由NHE 6表达减少和/或轴突生长或树枝化缺陷引起的相关疾病的个体。我们已经发表了关于小鼠模型中NHE 6功能的研究，但目前有必要过渡到患者来源的组织。潜在的人类治疗剂的筛选最好在人类（和患者来源的）组织中进行。本研究提出了三个具体目标：（1）确定NHE 6在调节内体腔酸度和内体再循环中的作用。(2)确定患者源性神经元中NHE 6突变对轴突生长中RAB 10相关SV功能的干扰程度。(3)通过外源性生长因子确定患者源性神经元中轴突生长和分支缺陷的可逆性。这项研究是创新的，因为我们正在研究自闭症的一种新的细胞机制，即轴生长中内体pH的调节。这项研究意义重大，因为它将导致开发急需的患者源性神经元艾德临床前模型，以及严重自闭症和相关疾病的潜在治疗方法，这是一个紧迫的公共卫生问题。

DESCRIPTION (provided by applicant): A lack of validated preclinical models for exploring cellular mechanisms has limited treatment development in severe autism. In order to develop new preclinical models and therapeutics, rig- orous studies of cell phenotypes and cellular responses to potential agents in patient-derived neurons will be advantageous. The long-term goal of this research is to elucidate the molecular mechanisms underlying the pathology of severe autism that will serve as the basis to develop innovative treatments for these patients with few current therapeutic options. We recently identi- fied a novel mechanism in autism involving endosomal Na+/H+ exchangers (NHEs). We have now generated induced pluripotent stem cell lines (iPSCs) from patients with a range of NHE6 mutations. The objective for this application is to elucidate the role of NHE6 in human axon de- velopment and to test the response of patient-derived neurons to available, mechanism-based agents that may subsequently serve as treatments in patients. NHE6 regulates the efflux of pro- tons from endosomes. In our preliminary studies in human neurons, NHE6 deficiency leads to over-acidification of the endosomal lumen and defects in axon growth and branching. This mechanism is fortuitous because there are a number of well-known FDA-approved agents that target intra-endosomal pH. Our central hypothesis is that deficiency of NHE6 inhibits axon growth and branching due to diminished polarized membrane addition. The rationale for this re- search is that it constitutes the first critical steps toward the development of new treatments for individuals with severe autism and related disorders caused by reductions in NHE6 expression and/or by defects in axonal growth or arborization. We have published studies on NHE6 function in mouse models, yet the transition to patient-derived tissues is warranted at this time. Screening of potential human therapeutic agents is best performed on human (and patient-derived) tis- sues. Three specific aims are proposed: (1) Determine the role of NHE6 in regulating endosome lumen acidity and endosome recycling. (2) Determine the extent to which the function of RAB10-associated SVs in axon growth is perturbed by NHE6 mutation in patient-derived neu- rons. (3) Determine the reversibility of axon growth and branching defects in patient-derived neurons by exogenous growth factors. The proposed research is innovative because we are studying a novel cellular mechanism in autism, namely, regulation of intra-endosomal pH in ax- on growth. This research is significant because it will lead to the development of critically need- ed preclinical models in patient-derived neurons and potential treatments for severe autism and related disorders, an urgent public health problem.