ROLE OF NEUREGULIN IN NEUROMUSCULAR SYNAPSE FORMATION

神经肌肉突触的形成需要突触前运动神经末梢和突触后肌肉纤维之间的一系列诱导性相互作用，从而形成高度专门化的突触前膜和突触后膜。突触后分化的一个方面是肌纤维突触核选择性上调肌乙酰胆碱受体(AChR)的表达。神经调节蛋白(NRG)是调节这种突触特异性转录的潜在信号，其受体定位于神经肌肉突触。NRG由运动神经元和肌肉细胞合成，能激活培养的肌肉细胞AChR基因的表达。因为NRG是由运动神经元和肌肉细胞合成的，并激活培养的肌肉细胞中AChR基因的表达。由于NRG也在心内膜组织中表达，并且是心脏发育所必需的，缺乏NRG表达的突变小鼠因心脏畸形而在胚胎第10天死于神经肌肉突触形成之前。因此，NRG在体内发育过程中可能在突触形成中所起的作用不能在NRG缺失突变的小鼠中进行评估。这项建议致力于研究NRG在神经肌肉突触形成中可能发挥的作用。本研究的一般方法是建立骨骼肌或运动神经元NRG选择性表达缺失的小鼠，交叉研究是将NRG/FLOX/FLOX小鼠与NRG+/-、MLCcre或NRG+/-；HB9cre小鼠杂交，建立骨骼肌或运动神经元选择性NRG表达缺失的小鼠。神经肌肉突触的形成将通过免疫组织化学程序进行分析，这将使我能够评估突触前和突触后的分化。这项研究将提供有关NRG信号在神经肌肉突触形成中的作用的信息，并可能为深入了解大脑神经元间突触的信号机制提供信息。

The formation of neuromuscular synapses requires a series of inductive interactions between presynaptic motor nerve terminals and postsynaptic muscle fibers, resulting in the formation of highly specialized pre- and post-synaptic membranes. One aspect of postsynaptic differentiation is the up-regulation of muscle acetylcholine receptor (AChR) expression selectively in synaptic nuclei of myofibers. Neuregulin (NRG), a potential signal for regulating such synapse-specific transcription, and its receptors are localized to neuromuscular synapses. NRG is synthesized both by motor neurons and muscle cells and activates AChR gene expression in cultured muscle cells. Because NRG is synthesized both by motor neurons and muscle cells and activates AChR gene expression in cultured muscle cells. Because NRG is also expressed in endocardial tissues and is required for heart development, mutant mice lacking NRG expression die at embryonic day 10, prior to neuromuscular synapse formation, due to heart malformation. Therefore, the role that NRG may play in synapse formation during development in vivo cannot be evaluated in NRG null- mutant mice. This proposal is devoted to study the role NRG may have in neuromuscular synapse formation. The general approach in this study is to produce mice lacking NRG expression selective in skeletal muscle or in motor neurons, by crossing study is to produce mice lacking NRG expression selectively in skeletal muscle or in motor neurons, by crossing NRG/flox/flox mice with NRG+/-; MLCcre or NRG+/-; HB9cre mice. The formation of neuromuscular synapses will be analyzed by immunohistochemical procedures that will allow me to assess both presynaptic and postsynaptic differentiation. This study will provide information on the function of NRG signaling in neuromuscular synapse formation and may provide insight into signaling mechanisms at interneuronal synapses in the brain.