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）中功能失调的分子通路是理解其发病机制和开发未来治疗方法的关键。在阿尔茨海默氏症和帕金森氏症中，在5-10%的遗传病例中鉴定出单基因突变，揭示了改变的核心分子途径，包括更大类别的散发病例。一个关键问题是，根据最近确定的定义突变和从头基因组拷贝数变异（占ASD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NHE 9（Na+/H+交换器9）的机制，将神经元活动的改变与突触连接的修改相结合。NHE 9是几个新发现的遗传联系之一，表明异常的内体运输和突触生长可能导致自闭症。我实验室的工作最近在果蝇中表征了突触生长和可塑性通路，其中突触后靶点以活性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途径的运输进行加工和调节。我们假设NHE 9的突变通过破坏内体pH值改变内体形成或内体区室中的配体-受体缔合，导致异常突触生长信号传导和可能导致自闭症行为的脑布线中的活性依赖性缺陷。内体表现出从早期内体（pH ~6.5）到溶酶体（pH ~4.5）的渐进性酸化，这对于内化的配体-受体复合物和细胞粘附蛋白的降解和再循环是必需的。与液泡V-ATP酶一起，NHE 9被预测为内体pH的关键分子决定因素，其通过将H+离子运输出该隔室而允许早期信号内体保持相对碱性，其中配体-受体对可以保持附着并传递突触生长信号。我们将确定内体运输缺陷是否存在于NHE 9突变体中，以及NHE 9活性是否可能与其他ASD突变体有关，包括突触细胞粘附蛋白如Neurexin和Neuroligin。新接触位点的产生可能需要通过内体系统去除或回收表面Neurexin和Neuroligin，这一过程可能需要NHE 9。在这些看似无关的蛋白质中连接一个共同的突触缺陷可能揭示了自闭症中功能失调的保守分子通路。