Neural circuit assembly features simultaneous targeting of numerous neuronal processes from constituent neuron types, yet the dynamics is poorly understood. Here, we use the Drosophila olfactory circuit to investigate dynamic cellular processes by which olfactory receptor neurons (ORNs) target axons precisely to specific glomeruli in the ipsi- and contralateral antennal lobes. Time-lapse imaging of individual axons from 30 ORN types revealed a rich diversity in extension speed, innervation timing, and ipsilateral branch locations and identified that ipsilateral targeting occurs via stabilization of transient interstitial branches. Fast imaging using adaptive optics-corrected lattice light-sheet microscopy showed that upon approaching target, many ORN types exhibiting “exploring branches” consisted of parallel microtubule-based terminal branches emanating from an F-actin-rich hub. Antennal nerve ablations uncovered essential roles for bilateral axons in contralateral target selection and for ORN axons to facilitate dendritic refinement of postsynaptic partner neurons. Altogether, these observations provide cellular bases for wiring specificity establishment.

神经电路组装的特点是同时靶向来自组成神经元类型的众多神经元过程，但动力学却知之甚少。在这里，我们使用果蝇嗅觉电路研究嗅觉受体神经元 (ORN) 将轴突精确定位到同侧和对侧触角叶中的特定肾小球的动态细胞过程。来自 30 种 ORN 类型的单个轴突的延时成像揭示了在延伸速度、神经支配时间和同侧分支位置方面的丰富多样性，并确定同侧靶向通过稳定瞬时间质分支发生。使用自适应光学校正晶格光片显微镜进行的快速成像显示，在接近目标时，许多表现出“探索分支”的 ORN 类型由从富含 F-肌动蛋白的集线器发出的基于平行微管的末端分支组成。触角神经消融揭示了双侧轴突在对侧目标选择中的重要作用，以及 ORN 轴突促进突触后伙伴神经元的树突细化的重要作用。总之，这些观察结果为建立布线特异性提供了细胞基础。