Commissural axons grow along complex pathways toward, across, and beyond the midline of the central nervous system. Taking commissural axons in the vertebrate spinal cord and the Drosophila ventral nerve cord as examples, we examine how commissural axon pathfinding is regulated by the Slit family of guidance cues and their Robo family receptors. We extract several principles that seem likely to apply to other axons and other contexts, such as the reiterative use of the same guidance molecules in distinct pathfinding decisions, the transcriptional specification of a pathway, the posttranscriptional regulation of growth along the pathway, and the possible role of feedback mechanisms to ensure the fidelity of pathfinding choices. Such mechanisms may help explain how a relatively small number of guidance molecules can generate complex and stereotyped wiring patterns. We also highlight the many gaps in our understanding of commissural axon pathfinding and question some widely accepted views. We hope that this review encourages further efforts to tackle these questions, in the expectation that this system will continue to reveal the general principles of axon pathfinding.

中文翻译：

---

狭缝及其Robo受体对连合轴突寻路的调节作用。

连合轴突沿着复杂的途径向中枢神经系统的中线，穿过中线和超出中线生长。以脊椎动物脊髓和果蝇腹侧神经系中的连合轴突为例，我们研究了导联线索的Slit家族及其Robo家族受体如何调控连合轴突寻路。我们提取了几条似乎可能适用于其他轴突和其他情况的原理，例如在不同的寻路决策中重复使用相同的指导分子，一条通路的转录说明，沿着该通路的转录后调控，以及可能的方法。反馈机制的作用，以确保寻路选择的忠诚度。这样的机制可以帮助解释相对较少数量的引导分子如何产生复杂且定型的布线图案。我们还强调了我们对连合轴突寻路的理解上的许多空白，并对一些被广泛接受的观点提出了质疑。我们希望这次审查鼓励进一步努力解决这些问题，以期该系统将继续揭示轴突寻路的一般原则。