PDF(Pubmed)
Abstract：
Visual circuit development is characterized by subdivision of neuropils into layers that house distinct sets of synaptic connections. We find that, in the Drosophila medulla, this layered organization depends on the axon guidance regulator Plexin A. In Plexin A null mutants, synaptic layers of the medulla neuropil and arborizations of individual neurons are wider and less distinct than in controls. Analysis of semaphorin function indicates that Semaphorin 1a, acting in a subset of medulla neurons, is the primary partner for Plexin A in medulla lamination. Removal of the cytoplasmic domain of endogenous Plexin A has little effect on the formation of medulla layers; however, both null and cytoplasmic domain deletion mutations of Plexin A result in an altered overall shape of the medulla neuropil. These data suggest that Plexin A acts as a receptor to mediate morphogenesis of the medulla neuropil, and as a ligand for Semaphorin 1a to subdivide it into layers. Its two independent functions illustrate how a few guidance molecules can organize complex brain structures by each playing multiple roles.
摘要：
视觉电路发展的特征是将神经质细分成容纳不同突触连接组的层。我们发现在果蝇髓质中，这种分层的组织取决于轴突指导调节神经丛蛋白A。在丛蛋白A无效突变体中，与对照组相比，髓质神经纤维的突触层和单个神经元的乔化更宽，更少。对信号素功能的分析表明信号素1a，作用于延髓神经元的子集，是髓质夹层中神经丛蛋白A的主要合作伙伴。去除内源性神经丛蛋白A的细胞质结构域对髓质层形成的影响要小得多；然而，丛蛋白A的无效和细胞质结构域缺失突变均导致延髓神经纤维的整体形状改变。这些数据表明神经丛蛋白A作为受体介导髓质神经纤维的形态发生，并作为信号素1a的配体将其细分为各层。它的两个独立功能说明了一些引导分子如何通过各自扮演多个角色来组织复杂的大脑结构。
