TRANSCRIPTIONAL MECHANISMS REGULATING ACTIVITY DEPENDENT GENE EXPRESSION

依赖活动的过程在发育过程中重塑神经系统和骨骼肌，需要将突触信号与基因表达的选择性变化耦合起来。这种类型的调控被称为“活动-转录耦合”。我们使用了大脑中NMDA受体和肌肉中编码收缩蛋白的基因的调节，作为活动-转录耦合的模型。我们以前已经证明，NMDA受体(NR)的NR2C亚单位在小脑中的表达需要神经活动，以及一种被称为neuRegin的营养因子。在目前的研究中，我们提供了证据表明，通过这两个受体的共同信号可能发生在突触。我们发现NMDA和ErbB受体在突触后密度(PSD)处富含，在那里它们与含有PDZ蛋白相互作用结构域的相同蛋白质相互作用。PDZ结构域蛋白很重要，因为它们将受体和通道搭建到信号分子上，从而将突触活动耦合到突触后神经元的信号级联反应中。我们还开始表征DNA调控序列，这些DNA调控序列在发育过程中调节受体的NR2A亚单位，并对神经活动做出反应。肌肉的慢抽动和快抽动特性是由运动神经元的细胞谱系和表观遗传信号决定的，运动神经元选择性地调节收缩基因的转录。为了了解选择性调节不同肌肉基因的信号通路，我们鉴定并鉴定了肌钙蛋白I慢(TnI)和快(TnIf)基因的增强子。我们的结果表明，转录因子的复合体与这些增强子相互作用，调节转录。使用酵母-1-杂交系统，我们分离出了赋予肌肉纤维类型特异性的假定因子。其中一个被称为GTF-3的因子编码一种具有5-6个内部重复的蛋白质，该蛋白质可能与一系列转录因子相互作用。有趣的是，在患有威廉姆斯-博伦综合征(WBS)的患者中，GTF-3基因以及该基因家族的另一个成员都被缺失了。威廉姆斯-博伦综合征是由染色体7q11.23上的微缺失引起的。据报道，WBS患者有不同程度的智力低下、主动脉瓣上狭窄和肌病。研究正在进行中，以了解GTF-3在与WBS相关的缺陷中的作用。

The activity-dependent processes that serve to remodel the nervous system and skeletal muscles during development, require the coupling of synaptic signals to selective changes in gene expression. This type of regulation is referred to as "activity-transcription coupling". We have used the regulation of NMDA receptors in the brain and of the genes encoding contractile proteins in muscle, as models for activity-transcription coupling. We demonstrated previously that the expression of the NR2C subunit of the NMDA receptor (NR) in cerebellum requires neural activity, as well as a trophic factor known as neuregulin. In the present studies, we provide evidence that co-signaling via these 2 receptors may occur at synapses. We found that NMDA and ErbB receptors are enriched at postsynaptic densities (PSD) where they interact with the same proteins harboring PDZ protein-protein interaction domains. The PDZ-domain proteins are important because they scaffold receptors and channels to signaling molecules, thus coupling synaptic activity to signaling cascades in the postsynaptic neurons. We have also begun to characterize the DNA regulatory sequences that regulate the NR2A subunits of the receptor during development and in response to neural activity. The slow- and fast-twitch properties of muscles are determined by cell lineage and epigenetic signals derived from motoneurons, which selectively regulate the transcription of contractile genes. To understand the signaling pathways that selectively regulate distinct muscle genes, we have identified and characterized the enhancers of the troponin I slow (TnIs) and fast (TnIf) genes. Our results suggest that a complex of transcription factors interact with these enhancers to regulate transcription. Using a yeast-1-hybrid system, we have isolated putative factors that confer muscle fiber-type-specificity. One of these factors, known as GTF-3, encondes a protein with 5-6 internal repeats that may interact with a series of transcription factors. Interestingly, the GTF-3 gene, as well another member of this gene family, is deleted in persons afflicted with the Williams-Beuren Syndrome (WBS) which results from a micro-deletion on chromosome 7q11.23. Persons with WBS are reported to have variable degrees of mental retardation, supra valvular aortic stenosis, and myopathies. Studies are in progress to understand the role of GTF-3 in the deficiencies associated with WBS.