Organophosphorus pesticides interact with ASD-linked neuroligins to alter synapto

描述（由申请人提供）：证据表明环境因素在自闭症谱系障碍（ASD）的发病机制中有重要作用，但增加ASD风险、严重程度和/或治疗结果的特定环境污染物仍有待确定。最近的人类研究将接触有机磷农药（OP）与ASD联系起来;然而，支持这种联系的生物学机制尚未得到描述。遗传学、组织学和功能成像数据暗示ASD病理学中突触连接的改变模式。neurexin（NRXN）-neuroligin（NLG）-SHANK信号通路在调节突触连接中至关重要，并且NLG突变是ASD的遗传风险因素。神经连接素与乙酰胆碱酯酶（一种已确立的OP分子靶标）具有序列、结构和功能同源性，表明神经连接素也可能是OP的靶标。基于这些观察结果，我推测，暴露的发育中的大脑OP通过干扰神经连接素介导的突触形成，稳定性和/或功能可塑性改变突触连接，这种影响是加剧ASD连锁突变的NLG基因编码神经连接素。为了验证这一新的假说，我将采用在发现神经连接素在突触连接中的作用过程中开发的体外模型来解决以下目标：（1）在突触密度、兴奋性突触与抑制性突触的比例和突触功能的水平上确定OP是否干扰原代培养的海马神经元中神经连接素介导的突触连接;和（2）确定与ASD相关的NLG突变的表达是否加剧了OP对体外突触连接的影响。我预计，OP，在浓度不抑制乙酰胆碱酯酶，将改变由培养的海马神经元形成的突触的数量，这将造成兴奋性抑制性突触的不平衡，并改变自发和诱发的神经元电活动。这些研究将提供有关OP和NLG突变如何融合以促进与ASD相关的不良神经发育结果的新机制信息，并将确定一种生物学机制，以证实将OP暴露与ASD风险增加联系起来的人类研究。识别OP作为ASD的环境风险因素将提供一个合理的机制，通过控制神经发育关键时期OP的暴露来预防ASD的发生和/或降低临床症状的严重程度。

DESCRIPTION (provided by applicant): Evidence suggests significant involvement of environmental factors in the pathogenesis of autism spectrum disorders (ASDs) but specific environmental contaminants that increase risk of ASDs, severity and/or treatment outcome remain to be identified. Recent human studies link exposure to organophosphorus pesticides (OPs) with ASDs; however, a biological mechanism supporting that link has yet to be described. Genetic, histological and functional imaging data implicate altered patterns of synaptic connectivity in ASD pathology. The neurexin (NRXN)-neuroligin (NLG)-SHANK signaling pathway is critically important in regulating synaptic connectivity, and NLG mutations are genetic risk factors for ASD. Neuroligin shares sequence, structural and functional homology with acetylcholinesterase, an established molecular target of OPs, suggesting that neuroligins may also be a target for OPs. Based on these observations, I hypothesize that exposure of the developing brain to OPs alters synaptic connectivity by interfering with neuroligin-mediated synapse formation, stabilization and/or functional plasticity, and this effect is exacerbated by ASD-linked mutations in the NLG genes that encode neuroligin. To test this novel hypothesis, I will adapt an in vitro model developed during discovery of the role of neuroligins in synaptic connectivity to address the following aims: (1) Determine whether OPs interfere with neuroligin-mediated synaptic connectivity in primary cultures of hippocampal neurons at the level of synapse density, the ratio of excitatory to inhibitory synapses and synaptic function; and (2) Determine whether expression of NLG mutations associated with ASDs exacerbate the effects of OPs on synaptic connectivity in vitro. I expect that OPs, at concentrations that do not inhibit acetylcholinesterase, will alter the number of synapses formed by cultured hippocampal neurons, which will create an imbalance of excitatory to inhibitory synapses and alter both spontaneous and evoked neuronal electrical activity. These studies will provide new mechanistic information about how OPs and NLG mutations converge to promote adverse neurodevelopmental outcomes of relevance to ASDs, and will identify a biological mechanism to corroborate human studies linking OP exposure to increased risk for ASDs. The identification of OPs as environmental risk factors for ASD will provide a rational mechanism for preventing the incidence of ASD and/or decreasing the severity of clinical symptoms by controlling exposures to OPs during critical periods of neurodevelopment.