INVESTIGATION OF PROTOCADHERIN-10 IN MEF2- AND FMRP-MEDIATED SYNAPSE ELIMINATION

描述（由申请人提供）：脆性X综合征（FXS）是迄今为止发现的最常见的智力迟钝和自闭症遗传形式。FXS是由Fmr1基因的转录沉默或功能缺失突变引起的，该基因编码脆性X智力迟钝蛋白（FMRP）。FXS最典型的表型之一是树突棘过多，树突棘是兴奋性突触的接触点，这与FXS由突触消除缺陷导致的观点有关。我们实验室最近的工作表明，FMRP是由转录因子肌细胞增强因子2 （MEF2； Pfeiffer等人，Neuron, 2010）触发的活性依赖性突触消除所必需的。有证据表明，FMRP可以调节MEF2产生的转录本的翻译或转运，从而介导突触的消除。该应用程序的拟议研究侧重于自闭症谱系障碍（ASD）基因，原钙粘蛋白-10 (PCDH10) (Morrow等人，Science, 2008)，旨在表征PCDH10介导的MEF2-和fmrp介导的突触消除的机制。我们的初步数据表明：1)PCDH10的表达受MEF2和FMRP的调控；2) PCDH10参与调节突触数量；3) PCDH10介导突触后支架蛋白PSD-95的泛素化和降解。电生理学和生化分析将被应用于了解PCDH10是否以及如何调节PSD-95的降解，并有助于mef2诱导的突触消除，这需要FMRP。这些实验数据将提供MEF2-和fmrp介导的突触消除的分子机制以及ASD基因在神经系统中的功能。

DESCRIPTION (provided by applicant): Fragile X Syndrome (FXS) is the most common inherited form of mental retardation and autism identified so far. FXS is caused by transcriptional silencing or loss-of-function mutations in the Fmr1 gene, which encodes for the Fragile X mental retardation protein (FMRP). One of the most characterized phenotypes of FXS is an excess of dendritic spines, the point of contact of excitatory synapses, which links the idea that FXS results from a deficit in synapse elimination. Recent work from our laboratory demonstrated that FMRP is required for activity- dependent synapse elimination triggered by the transcription factor Myocyte Enhancer Factor 2 (MEF2; Pfeiffer et al., Neuron, 2010). The evidence suggests that FMRP functions to regulate translation or transport of MEF2 generated transcripts to mediate synapse elimination. The proposed research of this application focuses on an autism-spectrum-disorders (ASD) gene, protocadherin-10 (PCDH10) (Morrow et al., Science, 2008) and aims to characterize the mechanisms underlying MEF2- and FMRP-mediated synapse elimination by PCDH10. Our preliminary data suggests that 1) the expression of PCDH10 is regulated by MEF2 and FMRP; 2) PCDH10 is involved in regulating synapse number; and 3) PCDH10 mediates ubiquitination and degradation of postsynaptic scaffold protein, PSD-95. Electrophysiology, as well as biochemical assays, will be applied to understand whether and how PCDH10 regulates PSD-95 degradation and contributes to MEF2-induced synapse elimination, which requires FMRP. The data from proposed experiments will provide molecular mechanism of MEF2- and FMRP-mediated synapse elimination as well as the function of an ASD gene in nervous system.