Research Institute of the McGill University Health Centre, Centre for Research in Neuroscience, Montréal, Québec, Canada.
Mol Brain. 2011 Apr 13;4:15. doi: 10.1186/1756-6606-4-15.
Establishing precise synaptic connectivity during development is crucial for neural circuit function. However, very few molecules have been identified that are involved in determining where and how many synapses form. The Plexin cell-surface molecules are a conserved family of axon guidance receptors that mediate axon fasciculation and repulsion during neural development, and later in development PlexinA receptors are involved in eliminating axonal branches and synapse numbers. Here we investigate the roles of PlexinA and PlexinB receptors in axonal branch and varicosity formation in Drosophila. We knocked down PlexinA or PlexinB expression using RNAi in identified mechanosensory neurons and analyzed axonal branching patterns and varicosity formations. Reducing PlexinA expression increased the axonal arbor complexity by increasing the number of branches and varicosities along the axon. In contrast, knocking down PlexinB expression decreased morphological complexity by decreasing the number of branches and the overall size of the axonal arbor, but did not reduce the number of varicosities. Our results demonstrate opposing roles for PlexinA and PlexinB in local wiring within a target region, where PlexinA functions to suppress excessive axonal branches and synapses and PlexinB facilitates axonal growth.
在发育过程中建立精确的突触连接对于神经回路功能至关重要。然而，只有极少数分子被确定参与决定何处以及形成多少个突触。Plexin 细胞表面分子是一个保守的轴突导向受体家族，在神经发育过程中介导轴突聚集和排斥，而在发育后期，PlexinA 受体参与消除轴突分支和突触数量。在这里，我们研究了 PlexinA 和 PlexinB 受体在果蝇中轴突分支和膨体形成中的作用。我们使用 RNAi 在已鉴定的机械感觉神经元中敲低 PlexinA 或 PlexinB 的表达，并分析了轴突分支模式和膨体形成。降低 PlexinA 的表达通过增加分支和沿着轴突的膨体的数量来增加轴突树突的复杂性。相比之下，敲低 PlexinB 的表达通过减少分支的数量和轴突树突的整体大小来降低形态复杂性，但不会减少膨体的数量。我们的结果表明 PlexinA 和 PlexinB 在靶区域内的局部布线中发挥相反的作用，其中 PlexinA 抑制过多的轴突分支和突触，而 PlexinB 促进轴突生长。
