Using Drosophila to Characterize the Molecular Pathogenesis of Autism

利用果蝇来表征自闭症的分子发病机制

• 批准号: 8641724
• 负责人: J. TROY LITTLETON
• 金额: $ 19.5万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2016-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8641724
• 关键词: Accounting; Alzheimer' s Disease; Autistic Disorder; Binding; Biological Assay; Biological Models; Brain; Categories; Cell Adhesion; Cell Adhesion Molecules; Cell membrane; Complex; Copy Number Polymorphism; Couples; Defect; Development; Disease; Drosophila genus; Early Endosome; Endosomes; Excision; Exhibits; Future; Gene Mutation; Generations; Genetic; Genome; Goals; Growth; Homologous Gene; Human; Ions; Label; Laboratories; Lead; Ligands; Link; Locales; Lysosomes; Modeling; Modification; Molecular; Movement; Mutation; Neurons; Parkinson Disease; Pathogenesis; Pathology; Pathway interactions; Physiology; Presynaptic Terminals; Process; Proteins; Receptor Activation; Recycling; Research; Signal Pathway; Signal Transduction; Signaling Molecule; Site; Subgroup; Surface; Synapses; Synaptic plasticity; System; Testing; Therapeutic; Therapeutic Intervention; Transgenic Organisms; Work; autism spectrum disorder; autistic behaviour; base; design; genetic manipulation; mutant; neurotrophic factor; null mutation; postsynaptic; presynaptic; public health relevance; receptor; receptor internalization; research study; signal processing; trafficking; transmission process; vacuolar H+-ATPase

DESCRIPTION (provided by applicant): Defining molecular pathways that are dysfunctional in autism and autistic spectrum disorders (ASDs) is key to understanding their pathogenesis and developing future therapeutics. In Alzheimer's and Parkinson's Disease, identification of single gene mutations in the 5-10% of genetic cases have revealed core molecular pathways that are altered, including in the larger category of sporadic cases. A key question is whether a similar molecular pathway(s) will emerge for autism based on the recent identification of defined mutations and de novo genome copy number variations that account for 10-20% of ASDs. Here, we propose to take advantage of genetic manipulations available in Drosophila to explore the mechanisms by which the autism-associated endosomal protein, NHE9 (Na+/H+ exchanger 9), couples alterations in neuronal activity to modifications of synaptic connectivity. NHE9 is one of several newly identified genetic links that indicate abnormal endosomal trafficking and synaptic growth may predispose to autism. Work from my lab has recently characterized a synaptic growth and plasticity pathway in Drosophila where postsynaptic targets release retrograde signals in an activity-dependent manner, triggering synaptic maturation and growth. These growth signals are processed and regulated through trafficking in the presynaptic endosomal pathway. We hypothesize that mutations in NHE9 alter endosomal formation, or ligand-receptor association in endosomal compartments, through disruption of endosomal pH, leading to abnormal synaptic growth signaling and activity-dependent defects in brain wiring that might contribute to autistic behavior. Endosomes exhibit a progressive acidification from early endosomes (pH ~6.5) to lysosomes (pH ~4.5) that is essential for degradation and recycling of internalized ligand-receptor complexes and cell adhesion proteins. Together with the vacuolar V-ATPase, NHE9 is predicted to be the key molecular determinant of endosomal pH by allowing early signaling endosomes to remain relatively basic by transporting H+ ions out of this compartment, where ligand-receptor pairs can remain attached and transmit synaptic growth signals. We will determine if endosomal trafficking defects are present in NHE9 mutants, and whether NHE9 activity may be linked to other ASD mutants that include synaptic cell adhesion proteins like Neurexin and Neuroligin. The generation of new contact sites is likely to require removal or recycling of surface Neurexin and Neuroligin through the endosomal system, a process that may require NHE9. Linking a common synaptic defect in these seemingly unrelated proteins may reveal a conserved molecular pathway that is dysfunctional in autism.

描述（由申请人提供）：定义自闭症和自闭症谱系障碍（asd）中功能失调的分子途径是了解其发病机制和开发未来治疗方法的关键。在阿尔茨海默病和帕金森病中，在5-10%的遗传病例中发现的单基因突变揭示了核心分子通路的改变，包括在更大类别的散发性病例中。一个关键的问题是，基于最近确定的突变和新生基因组拷贝数变异（占自闭症的10-20%），自闭症是否会出现类似的分子途径。在这里，我们建议利用果蝇中可用的遗传操作来探索自闭症相关的内体蛋白NHE9 （Na+/H+交换9）将神经元活动的改变与突触连通性的改变耦合在一起的机制。NHE9是新发现的几个遗传联系之一，表明异常的内体运输和突触生长可能易患自闭症。我的实验室最近研究了果蝇的突触生长和可塑性通路，其中突触后靶点以活动依赖的方式释放逆行信号，触发突触成熟和生长。这些生长信号通过突触前内体通路的运输被加工和调节。我们假设NHE9的突变通过破坏内体pH改变内体形成或内体隔室中的配体-受体结合，导致突触生长信号异常和脑线路中活动依赖性缺陷，这可能导致自闭症行为。核内体表现出从早期核内体（pH ~6.5）到溶酶体（pH ~4.5）的逐渐酸化，这是内化配体-受体复合物和细胞粘附蛋白降解和再循环所必需的。与空泡v - atp酶一起，NHE9被预测为内体pH的关键分子决定因素，它允许早期信号内体通过将H+离子运输出这个腔室来保持相对碱性，在这个腔室中配体-受体对可以保持连接并传递突触生长信号。我们将确定NHE9突变体中是否存在内体运输缺陷，以及NHE9活性是否可能与其他ASD突变体相关，包括突触细胞粘附蛋白如Neurexin和Neuroligin。新的接触位点的产生可能需要通过内体系统去除或再循环表面Neurexin和Neuroligin，这一过程可能需要NHE9。将这些看似不相关的蛋白质中常见的突触缺陷联系起来，可能会揭示自闭症中功能失调的保守分子途径。