Olivocerebellar Circuitry in Autism

自闭症是一种发育障碍，受影响的人大脑功能发生变化，破坏了他们执行特定运动和认知任务的能力。该项目的主要长期目标是确定在主要受影响的大脑区域小脑中，基于关键传入投射和靶神经元早期发育的错误，突触水平的连接性变化是如何受到干扰的。谷氨酸能苔藓纤维、橄榄小脑爬行纤维和平行纤维均存在于关键的小脑皮质神经元上的突触，其中一些在自闭症时表现为神经病理改变。这项研究的主要目的集中在小脑皮质两个不同功能部分的关键谷氨酸转运体和受体，即最近被认为与认知功能有关的后叶CRU II区和前叶重要的感觉运动基础作用的Vermis小叶VI区。谷氨酸能定量测量将与自闭症诊断访谈-修订版(ADI-R)的互惠社交、交流以及刻板印象和重复运动行为领域的分数相关。为了实现这些目标，在10例成人(16-30岁)自闭症尸检病例和10例年龄、性别和死亡时间相匹配的对照组中，提出了四个具体目标。第一个特定目标将在第一年完成，使用组织学配体结合来确定关键的离子型受体(AMPAR，NMDAR)和代谢型谷氨酸受体(MGluR1)在CRU II和小叶VI的三个板层中的数量和配体结合亲和力，这些是小脑传入的靶标。第二个特定目标将在第一年完成，在相同的小脑区域使用原位杂交组织化学来定量三种类型的突触后谷氨酸受体亚型(AMPAR1，NMDAR1和mGluR1)的mRNA水平。第三个具体目标是在第一年进行试验，并于第二年完成，量化PC末端关键谷氨酸转运体的密度(Le.，兴奋性氨基酸转运体4型，EAAT4；主要包裹在攀升突触周围的Bergmann神经胶质细胞膜上(EAA T1，L-谷氨酸/L-天冬氨酸转运体，GLAST)；以及谷氨酸受体(Glu-Ro2)，它对诱导长期抑郁(LTD)很重要，并且主要定位于PC上的平行纤维突触。GluRo2和PSD93的共同定位将决定突触后密度的百分比，而EAAT4和突触素的共同定位将决定突触前密度的百分比。最终的具体目标将在第二年完成，采用翻译的方法，评估谷氨酸受体、转运体和突触密度与自闭症诊断访谈修订版(ADI-R)测量的社交沟通和重复行为症状严重程度的关系。本研究旨在研究两个功能不同的小脑区域中关键兴奋性谷氨酸成分(S)的显著变化是否与临床病例中孤独症的症状类型和严重程度有不同的关系。这项为期两年的研究的数据将有助于描绘自闭症患者的核心神经底物，并应有助于指导遗传学家在自闭症中寻找可能的候选基因。此外，了解这个模型区域内的细胞和分子机制有助于我们理解目前自闭症患者的药物治疗方法，并可能建议针对神经基质的新治疗方法。

Autism is a developmental disorder and affected individuals have alterations in brain function disrupting their ability to perform particular motor and cognitive tasks. The main long term objective of this project is to determine in one major affected brain region, the cerebellum, how changes in connectivity at the synaptic level are disturbed based on errors in the early development of key afferent projections and target neurons. Glutamatergic mossy fibers, olivocerebellar climbing fibers and parallel fibers all synapse on key cerebellar cortical neurons, some of which show neuropathological changes in autism. The major objective of this study focuses on key glutamatergic transporters and receptors in two functionally distinct parts of the cerebellar cortex, the Crus II area in the posterior lobe recently implicated in cognitively-based functions and vermis lobule VI in the anterior lobe important for sensorimotor-based roles. Quantitative glutamatergic measures will be related to scores from the Autism Diagnostic Interview-Revised (ADI-R) for reciprocal social interaction, communication, and stereotyped and repetitive motor behavior domains. To accomplish these objectives, four specific aims are proposed in ten adult (age 16-30 years old) autistic post-mortem cases and ten age-, gender and postmortem interval-matched controls. The first specific aim, to be completed in the first year, uses histological ligand binding to determine the number and ligand binding affinity of key ionotropic (AMPAR, NMDAR) and metabotropic glutamate receptors (mGluR1) in the three laminae of Crus II and lobule VI, targets for cerebellar afferents. The second specific aim, to be completed in the first year, uses in situ hybridization histochemistry in the same cerebellar regions to quantify the mRNA levels of three types of postsynaptic glutamate receptor subtypes (AMPAR1, NMDAR1 and mGluR1). The third specific aim with trials in the first year and completed in the second year, quantifies the densities of key glutamate transporters at terminals ending on PCs (Le., excitatory amino acid transporter type 4, EAAT4; on membranes of Bergmann glia that predominately wrap around climbing synapses (EAA T1, L-glutamate/L-aspartate transporter, GLAST); and a glutamate receptor (GluRo2) that is important for induction of long-term depression (LTD) and is predominately localized to parallel fiber synapses on PCs. Co-localization of GluRo2 with PSD93 will determine the percentage of postsynaptic density and co-localization of EAAT4 with synaptophysin will determine the percentage of presynaptic density. The final specific aim, to be completed in the second year, takes a translational approach and evaluates the relationships of glutamate receptors, transporters and synaptic density to severity of social-communicative and repetitive behavior symptoms as measured by the Autism Diagnostic Interview - Revised (ADI-R). This aim examines whether significant changes in key excitatory glutamate component(s) in the two functionally distinct cerebellar regions relate differentially to autism symptom type and severity in the clinical cases. Data from these studies over the two year project will help delineate core neural substrates in autistic individuals and should help guide geneticists in their search for possible candidate genes in the disorder. Furthermore, understanding the cellular and molecular mechanisms within this model region could contribute to our understanding of current pharmacotherapeutic treatments of autistic individuals and may suggest novel treatments targeted to neural substrates.