Bentley D, Toroian-Raymond A
Nature. 1986;323(6090):712-5. doi: 10.1038/323712a0.
A major question in developmental neurobiology is how developing nerve cells accurately extend processes to establish connections with their target cells. This problem involves both the nature of cues for growth cone guidance and also the question of how growth cones survey their environment for cues and respond by altering their direction of migration. The filopodia which normally extend from neuronal growth cones have been shown to affect growth cone steering in vitro and it has been proposed that they function in vivo in the detection of and response to guidance cues. This hypothesis could be tested in vivo if growth cones which normally have filopodia could be induced to migrate in their absence. The pair of Ti1 neurones are the first neurones to extend axons through the limb buds of embryonic grasshoppers. We report here an examination of the migration of Ti1 pioneer growth cones deprived of filopodia by culture in agents which disrupt actin microfilaments. Under these conditions, axons continue to extend but a large percentage of growth cones are highly disoriented. Our results indicate that Ti1 filopodia are not necessary for axonal elongation in vivo but that they are important for correctly oriented growth cone steering.
发育神经生物学中的一个主要问题是，发育中的神经细胞如何精确地延伸突起以与靶细胞建立连接。这个问题既涉及生长锥导向线索的性质，也涉及生长锥如何在其环境中探寻线索并通过改变迁移方向做出反应的问题。通常从神经元生长锥延伸出的丝状伪足已被证明在体外会影响生长锥的转向，并且有人提出它们在体内发挥作用，用于检测导向线索并对其做出反应。如果能够诱导通常具有丝状伪足的生长锥在没有丝状伪足的情况下迁移，那么这个假设就可以在体内进行验证。Ti1神经元对是第一批通过胚胎蝗虫的肢芽延伸轴突的神经元。我们在此报告了一项对Ti1先驱生长锥迁移的研究，这些生长锥通过在破坏肌动蛋白微丝的试剂中培养而被剥夺了丝状伪足。在这些条件下，轴突继续延伸，但很大比例的生长锥高度迷失方向。我们的结果表明，Ti1丝状伪足在体内对于轴突伸长不是必需的，但对于正确定向的生长锥转向很重要。
