Keshishian H, Chang T N, Jarecki J
Department of Biology, Yale University, New Haven, Connecticut 06520.
FASEB J. 1994 Jul;8(10):731-7. doi: 10.1096/fasebj.8.10.8050672.
Synaptogenesis can be analyzed in a simple array of motoneurons and muscle fibers of the embryos and larvae of Drosophila melanogaster. Each abdominal hemisegment contains a stereotypic array of 30 muscle fibers. During middle to late embryogenesis, motoneurons exit the central nervous system to make precise synaptic connections with specific muscle fibers. Target recognition has been tested using both genetic and microsurgical manipulations, which indicate that motoneurons actively recognize specific muscle fibers. The molecular basis of target recognition has been examined by screens for mutations that disrupt both guidance events and correct innervation. In addition, the motoneurons and muscle fibers both express an array of putative cell adhesion molecules whose functions may contribute to normal connectivity. Postsynaptic specializations, including glutamate receptor distribution, depend on innervation and neural activity. The neuromuscular system is not "hardwired," as motoneurons are capable of altering both their branch arborizations and connectivity in response to local denervation and blockade of synaptic function. Collectively, these studies show that the Drosophila motor innervation is a powerful model system for testing at the cellular and molecular level the mechanisms that govern synaptic development.
在黑腹果蝇胚胎和幼虫的运动神经元与肌纤维的简单排列中，可以对突触发生进行分析。每个腹部半体节包含30根肌纤维的定型排列。在胚胎发育中后期，运动神经元离开中枢神经系统，与特定的肌纤维建立精确的突触连接。已通过遗传和显微外科操作对靶标识别进行了测试，结果表明运动神经元能主动识别特定的肌纤维。通过筛选破坏导向事件和正确神经支配的突变，研究了靶标识别的分子基础。此外，运动神经元和肌纤维都表达一系列假定的细胞粘附分子，其功能可能有助于正常的连接。包括谷氨酸受体分布在内的突触后特化取决于神经支配和神经活动。神经肌肉系统并非“硬连线”，因为运动神经元能够响应局部去神经支配和突触功能阻断，改变其分支树突和连接。总体而言，这些研究表明，果蝇运动神经支配是一个强大的模型系统，可在细胞和分子水平上测试控制突触发育的机制。
