Regulation of Utrophin Promoter in Muscle

描述（由申请人提供）：肌营养不良蛋白（肌营养不良蛋白相关蛋白）与肌营养不良蛋白具有广泛的序列同源性和组织基序，被认为是肌营养不良蛋白的常染色体同源物。 实际上，肌营养不良蛋白的转基因过表达可以在功能上替代缺失的肌营养不良蛋白分子，并逆转mdx（营养不良）小鼠肌肉中的营养不良病理生理学。 utrophin基因虽然广泛表达，但在发育、再生以及成熟骨骼肌中具有高度调节的亚细胞分布。 在成熟的肌纤维（细长的多核细胞）中，utrophin在突触或神经肌肉接头（NMJ）处富集。肌纤维中utrophin的空间分布与烟碱乙酰胆碱受体（nACHR）的分布在很大程度上平行，特别是它们受运动神经释放生长和分化因子（例如heregulin）影响的方式。 在NMJ发生nACHR和utrophin的选择性富集，部分原因是它们的信息优先在突触下核转录，而不是沿着肌纤维的长度分散的核。 我们和其他人最近证明，轴突相关生长因子调蛋白利用ERK（MAP激酶）信号传导途径促进GABPa/B转录因子复合物与utrophin启动子的N-Box基序的结合，从而激活启动子并增加培养的肌肉细胞中utrophin基因的表达。 目前关于肌营养蛋白在肌肉中的表达调节的假说集中在突触下核的肌营养蛋白的N-box依赖性区室化转录上。 我们推测，额外的反式作用因子存在和调节utrophin启动子。 我们还推测这些反式作用因子和信号通路之间的协同作用在utrophin启动子调控中起作用。在我们的初步研究中，我们已经确定了额外的反式作用因子，它们的信号通路，并描述了它们在utrophin启动子调控的协同作用;我们还研究了调蛋白介导的utrophin启动子在小鼠肌肉中的激活，在体内。 在这个建议中，我们计划扩展这些研究，以更好地了解在骨骼肌肌营养因子启动子调控的分子机制。

DESCRIPTION (provided by applicant): Utrophin (dystrophin related protein) shares extensive sequence homology and organizational motifs with dystrophin, and is considered to be the autosomal homolog of dystrophin. Indeed, transgenic over expression of utrophin can functionally substitute for the missing dystrophin molecule and reverse the dystrophic patho-physiology in the muscles of mdx (dystrophic) mice. The utrophin gene, while ubiquitously expressed, has a highly regulated sub-cellular distribution during development, regeneration as well as in mature skeletal muscle. In mature myofibers (elongated multi-nucleated cells), utrophin is enriched at the synapse or neuromuscular junction (NMJ). The spatial distribution of utrophin in myofibers parallels the distribution of nicotinic acetylcholine receptors (nACHR) to a remarkable degree, in particular, the manner in which they are influenced by the release of growth and differentiation factors (e.g. heregulin) from motor nerves. Selective enrichment of nACHR and utrophin at the NMJ occurs, in part, due to their messages being preferentially transcribed at sub-synaptic nuclei rather than nuclei scattered along the length of the myofiber. We and others, recently demonstrated that the neurite-associated growth factor heregulin utilizes the ERK (MAP kinase) signaling pathway to promote the binding of the GABPa/b transcription factor complex to the N-Box motif of the utrophin promoter, thus activating the promoter and increasing utrophin gene expression in cultured muscle cells. Current hypotheses on the regulation of utrophin expression in muscle center on N-box dependent compartmentalized transcription of utrophin at sub-synaptic nuclei. We hypothesize that additional trans-acting factors exist and regulate the utrophin promoter. We also hypothesize that co-operability among these trans-acting factors and signaling pathways plays a role in utrophin promoter regulation. In our preliminary studies, we have identified additional trans-acting factors, their signaling pathways and describe their co-operability in utrophin promoter regulation; we have also studied heregulin mediated utrophin promoter activation in mouse muscle, in vivo. In this proposal we plan to extend these studies to better understand the molecular mechanisms of utrophin promoter regulation in skeletal muscle.