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与突触后肌纤维之间的一系列诱导相互作用，从而形成高度特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，激活培养肌肉细胞中AChR基因的表达。因为NRG可由运动神经元和肌肉细胞合成，并激活培养肌肉细胞中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，因此缺乏NRG表达的突变小鼠在胚胎第10天，即神经肌肉突触形成之前，由于心脏畸形而死亡。因此，无法在NRG零突变小鼠体内评估NRG在发育过程中突触形成中可能发挥的作用。本提案致力于研究NRG在神经肌肉突触形成中的作用。本研究的一般方法是选择性制备骨骼肌或运动神经元缺乏NRG表达的小鼠，通过交叉研究，通过NRG/flox/flox小鼠与NRG+/-杂交，选择性制备骨骼肌或运动神经元缺乏NRG表达的小鼠；MLCcre或NRG+/-；HB9cre老鼠。神经肌肉突触的形成将通过免疫组织化学方法进行分析，这将使我能够评估突触前和突触后的分化。本研究将提供NRG信号在神经肌肉突触形成中的功能信息，并可能为大脑神经元间突触的信号传导机制提供见解。

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.