Faculty of Life Sciences, Wellcome Trust Centre for Cell-Matrix Research, Manchester M13 9PT, United Kingdom.
Dev Neurobiol. 2010 Jan;70(1):58-71. doi: 10.1002/dneu.20762.
The formation of neuronal networks, during development and regeneration, requires outgrowth of axons along reproducible paths toward their appropriate postsynaptic target cells. Axonal extension occurs at growth cones (GCs) at the tips of axons. GC advance and navigation requires the activity of their cytoskeletal networks, comprising filamentous actin (F-actin) in lamellipodia and filopodia as well as dynamic microtubules (MTs) emanating from bundles of the axonal core. The molecular mechanisms governing these two cytoskeletal networks, their cross-talk, and their response to extracellular signaling cues are only partially understood, hindering our conceptual understanding of how regulated changes in GC behavior are controlled. Here, we introduce Drosophila GCs as a suitable model to address these mechanisms. Morphological and cytoskeletal readouts of Drosophila GCs are similar to those of other models, including mammals, as demonstrated here for MT and F-actin dynamics, axonal growth rates, filopodial structure and motility, organizational principles of MT networks, and subcellular marker localization. Therefore, we expect fundamental insights gained in Drosophila to be translatable into vertebrate biology. The advantage of the Drosophila model over others is its enormous amenability to combinatorial genetics as a powerful strategy to address the complexity of regulatory networks governing axonal growth. Thus, using pharmacological and genetic manipulations, we demonstrate a role of the actin cytoskeleton in a specific form of MT organization (loop formation), known to regulate GC pausing behavior. We demonstrate these events to be mediated by the actin-MT linking factor Short stop, thus identifying an essential molecular player in this context.
神经元网络的形成，无论是在发育过程中还是在再生过程中，都需要轴突沿着可重复的路径向其适当的突触后靶细胞延伸。轴突的延伸发生在轴突末端的生长锥（GC）处。GC 的前进和导航需要其细胞骨架网络的活动，该网络由片状伪足和丝状伪足中的丝状肌动蛋白（F-actin）以及源自轴突核心束的动态微管（MT）组成。尽管部分阐明了控制这两种细胞骨架网络的分子机制、它们之间的串扰以及它们对外界信号线索的反应，但仍阻碍了我们对 GC 行为如何受到调控变化控制的概念理解。在这里，我们引入果蝇 GC 作为一种合适的模型来解决这些机制。果蝇 GC 的形态和细胞骨架读数与其他模型（包括哺乳动物）相似，如 MT 和 F-actin 动力学、轴突生长速率、丝状伪足结构和运动、MT 网络的组织原则以及亚细胞标记物定位等方面。因此，我们预计在果蝇中获得的基本见解可以转化为脊椎动物生物学。与其他模型相比，果蝇模型的优势在于其对组合遗传学的巨大适应性，这是解决调节轴突生长的复杂调控网络的有力策略。因此，我们通过药理学和遗传学操纵，证明了肌动蛋白细胞骨架在特定形式的 MT 组织（环形成）中的作用，这种作用已知可以调节 GC 暂停行为。我们证明这些事件是由肌动蛋白-MT 连接因子 Short stop 介导的，从而确定了该过程中的一个重要分子参与者。
