Neural Pathfinding in an Insect Wing

为了了解神经细胞的轴突如何沿着特定的路径在特定的方向上导航，我们正在简单系统中研究轴突生长的基质。轴突的生长可以很容易地在昆虫翅膀中进行研究，其中神经元形成一个简单的二维网络，坐落在两个单层上皮细胞之间的空间中。从上层移植物的转位表明，生长的轴突是由上皮基质的分级线索引导的，从远端到近端方向。利用扫描电子显微镜，这一基底的地形已被完整地观察到。轴突在近端生长时，基底细胞突的密度增加。表面分子沿神经通路的分布可以通过这些基础过程的伸展和收缩来调节。在轴突生长时在基质表面发现的一种新蛋白（2F5）被认为参与了轴突与基质的相互作用。该蛋白已被纯化，其促进轴突生长的能力将通过原位功能测定和扫描电子显微镜进行研究。此外，一种免疫抑制技术将用于产生针对其他可能参与轴突寻路的表面蛋白的抗体。这些研究有望识别出在神经发育和再生中起作用的新分子，不仅在昆虫中，而且在其他物种中也是如此。

To understand how axons of nerve cells navigate in particular directions along defined pathways, the substratum for axonal growth is being examined in the simple system. Growth of axons can easily be studied in an insect wing where neurons form a simple, two- dimensional network nestled in the space between two monolayers of epithelial cells. Transposition of grafts from the upper monolayer suggests that growing axons are guided in a distal to proximal direction by graded cues in their epithelial substratum. Using scanning electron microscopy, the topography of this substratum has been viewed in its entirety. Axons encounter an increasing density of basal cellular processes as they grow proximally. The distribution of surface molecules along the neural pathway can be modulated by extension and retraction of these basal processes. A novel protein (2F5) found on surfaces of the substratum at the time of axonal outgrowth is thought to be involved in the interaction of axons with substrata. This protein has been purified and its ability to promote outgrowth of axons will be studied using functional assays in situ and scanning electron microscopy. In addition, an immunosuppression technique will be used to generate antibodies to other surface proteins that may be involved in axonal pathfinding. These studies promise to identify novel molecules that play a role in neuronal development and regeneration, not only in the insect, but in other species, as well.