Neurexins and neuroligins are common synaptic adhesion molecules that are associated with autism and interact with each other in the synaptic cleft. The Drosophila neuromuscular junction (NMJ) bouton is a well-known model system in neuroscience, and ghost and satellite boutons, respectively, indicate the poor development and overgrowth of the NMJ boutons. However, the Drosophila neurexin (DNrx) and Drosophila neuroligins (DNlgs) are mainly observed in type Ib boutons, indicating the ultrastructural and developmental phenotypes of the Drosophila NMJ. Here, we identified the ultrastructural and developmental features of ghost and satellite boutons by utilizing dneurexin (dnrx) and dneuroligins (dnlgs) fly mutants and other associated fly strains. Ghost boutons contain synaptic vesicles with multiple diameters but very rarely contain T-bar structures and swollen or thin subsynaptic reticulum (SSR) membranes. The muscle cell membrane is invaginated at different sites, stretches to the ghost bouton from different directions, forms several layers that enwrap the ghost bouton, and then branches into the complex SSR. Satellite boutons share a common SSR membrane and present either a typical profile in which a main bouton is encircled by small boutons or two atypical profiles in which the small boutons are grouped together or distributed in beads without a main bouton. Electron and confocal microscopy data showed that dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 mutations led to ghost boutons; the overexpression of dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 led to satellite boutons; and the dnlg2;dnlg3 double mutation also led to satellite boutons. These results suggested that DNrx and DNlgs jointly maintain the development and function of NMJ boutons by regulating the balance of ghost and satellite boutons in Drosophila.

中文翻译：

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Neurexin和Neuroligins在果蝇神经肌肉交界处保持鬼魂和卫星Boutons的平衡。

神经毒素和神经胶蛋白是常见的突触粘附分子，与自闭症相关并在突触裂隙中相互作用。果蝇神经肌肉接头（NMJ）钮扣是神经科学中众所周知的模型系统，而鬼钮和卫星钮扣分别表示NMJ钮扣的不良发育和过度生长。然而，果蝇神经毒素（DNrx）和果蝇神经胶蛋白（DNlgs）主要在Ib型boutons中观察到，表明果蝇NMJ的超微结构和发育表型。在这里，我们通过利用dneurexin（dnrx）和dneuroligins（dnlgs）苍蝇突变体以及其他相关的苍蝇品系，鉴定了幽灵和卫星钮扣的超微结构和发育特征。幽灵钮扣包含具有多个直径的突触小泡，但极少包含T型杆结构和突触网状膜（SSR）肿胀或薄。肌肉细胞膜在不同的部位被内陷，从不同的方向延伸到鬼钮扣，形成包裹鬼钮扣的几层，然后分支成复杂的SSR。卫星钮扣共有一个共同的SSR膜，或者呈现典型的轮廓，其中主要纽扣由小钮扣包围，或者具有两个非典型轮廓，其中小型钮扣被分组在一起或散布在没有主钮扣的小珠中。电子显微镜和共聚焦显微镜数据显示，dnrx，dnlg1，dnlg2，dnlg3和dnlg4突变导致鬼弹。dnrx，dnlg1，dnlg2，dnlg3和dnlg4的过度表达导致卫星弹跳；和dnlg2; dnlg3双重突变也导致卫星反弹。这些结果表明，DNrx和DNlgs通过调节果蝇中的幽灵和卫星按钮的平衡来共同维持NMJ按钮的发展和功能。