Cell adhesion molecules in autism: a whole-brain study of genetic mouse models

描述(由申请人提供)：自闭症包括一系列高度可遗传的疾病，目前相关的易感基因正在通过大规模基因组学项目进行鉴定。自闭症基因鉴定的一个重要成果是有可能使用遗传小鼠模型来研究这些基因影响大脑发育和功能的电路、细胞和分子机制。目前的项目集中在三个携带细胞黏附分子(CAM)突变的小鼠模型上：神经连接素3R451C，神经连接素4缺失和cntnap2缺失小鼠。这些小鼠被选为与自闭症相关的一个更大的突触基因家族的代表，其中包括神经连接蛋白、Neurexins、Cntnap、钙粘蛋白、Contact和Shank蛋白。这些基因罕见突变的发现为突触成熟和功能在自闭症中的作用提供了强有力的支持。目前的提案旨在开始剖析三种小鼠模型的潜在电路和细胞机制。为了能够比较不同自闭症小鼠模型的脑功能，我们开发了一种新的方法来对整个小鼠的大脑进行高通量成像。这种方法，我们称之为连续双光子(STP)断层成像，集成了双光子激光扫描显微镜和组织切片。为了通过STP断层扫描研究脑功能，我们使用表达绿色荧光蛋白(GFP)的转基因c-fos-GFP小鼠作为报告基因，诱导即刻早期基因c-fos。这使我们能够识别具有异常c-fos诱导的大脑区域，进而识别在行为任务或全身药物应用过程中诱发的神经激活。这些异常区域-自闭症相关病理的候选大脑区域-然后成为详细的电生理和解剖学研究的重点，旨在确定确切的潜在电路和细胞机制。具体目标是：1。研究CAM突变如何影响调节社会行为的大脑回路。2.研究细胞黏附分子(CAM)基因突变对大脑皮层振荡活动和脑兴奋与抑制平衡的影响。3.研究候选脑区的解剖连通性和细胞生理学。 我们相信，拟议中的实验的成功完成将为自闭症患者突触基因下游的大脑功能的神经发育变化提供机械性的见解。我们的最终目标是利用这些结果来为未来治疗策略的开发和测试制定假设。

DESCRIPTION (provided by applicant): Autism comprises a spectrum of highly heritable disorders and today the relevant susceptibility genes are being identified by large scale genomics projects. An important outcome of the identification of autism genes is the possibility to use genetic mouse models to study circuit, cellular and molecular mechanisms by which these genes affect brain development and function. The current project is focused on three mouse models carrying mutations in cell adhesion molecules (CAMs): the neuroligin 3 R451C, neuroligin 4 null, and Cntnap2 null mice. These mice were selected as representatives of a larger family of synaptic genes linked to autism, which includes neuroligins, neurexins, Cntnap, cadherin, contactin, and Shank proteins. The identification of rare mutations in these genes provides a strong support for the role of synaptic maturation and function in autism. The current proposal aims to begin to dissect the underlying circuit and cellular mechanisms in the three mouse models. In order to be able to compare brain functions in different autism mouse models, we have developed a novel method for high-throughput imaging of whole mouse brains. This method, which we call serial two- photon (STP) tomography, integrates two-photon laser-scanning microscopy and tissue sectioning. To study brain functions by STP tomography, we use transgenic c-fos-GFP mice that express green fluorescent protein (GFP) as a reporter for the induction of the immediate early gene c-fos. This allows us to identify brain regions with abnormal c-fos induction, and by extension neural activation, evoked during behavioral tasks or by systemic drug applications. Such abnormal regions-candidate brain areas for autism-related pathology-then become the focus of detailed electrophysiological and anatomical studies, which aim to determine the exact underlying circuit and cellular mechanisms. The Specific Aims are: 1. To study how CAM mutations affect brain circuits mediating social behavior. 2. To study how CAM mutations affect oscillatory cortical activity and the balance of brain excitation and inhibition. 3. To study anatomical connectivity and cellular physiology of candidate brain regions. We believe that a successful completion of the proposed experiments will provide mechanistic insights into neurodevelopmental changes in brain functions that lie downstream of the synaptic genes in autism. Our ultimate goal is to use such results to formulate hypotheses for the development and testing of therapeutic strategies in the future.