Comm function in commissural axon guidance:: cell-autonomous sorting of Robo in vivo
Comm function in commissural axon guidance:: cell-autonomous sorting of Robo in vivo
复制标题
DOI：
10.1038/nn1388
复制
发表时间：
2005-02-01
影响因子：
25
通讯作者：
Dickson, BJ
中科院分区：
文献类型：
--
作者：
Keleman, K;Ribeiro, C;Dickson, BJ
Commissueless（Comm）通过调节中线排斥剂Slit的受体Robo的表面水平来控制穿过果蝇中线的轴突引导。已经提出了两种不同的模型来研究Comm如何调节Robo：“分选”模型和“清除”模型，这两种模型都是基于体外使用异源细胞的研究。在这里，我们在体内测试这两种模型。我们建立了一个基因拯救测定Comm，并使用此测定表明，中线穿越不需要中线细胞中的Comm的存在下，所提出的清除模型。此外，通过监测活胚胎中Robo-green荧光蛋白（GFP）融合的运输，我们证明了Comm阻止Robo-GFP向生长锥的传递，正如分选模型所预测的那样。也有人提出，Comm必须被Nedd 4泛素连接酶泛素化。然而，我们在这里表明，在体外或体内，Comm的泛素化不是其功能所必需的，并且Nedd 4不太可能在中线的轴突引导中起作用。
Commissureless (Comm) controls axon guidance across the Drosophila melanogaster midline by regulating surface levels of Robo, the receptor for the midline repellent Slit. Two different models have been proposed for how Comm regulates Robo: a 'sorting' model and a 'clearance' model, both based on studies using heterologous cells in vitro. Here, we test these two models in vivo. We establish a genetic rescue assay for Comm, and use this assay to show that midline crossing does not require the presence of Comm in midline cells, as proposed by the clearance model. Moreover, by monitoring the trafficking of a Robo-green fluorescent protein (GFP) fusion in living embryos, we demonstrate that Comm prevents the delivery of Robo-GFP to the growth cone, as predicted by the sorting model. It has also been suggested that Comm must be ubiquitinated by the Nedd4 ubiquitin ligase. We show here, however, that ubiquitination of Comm is not required for its function in vitro or in vivo, and that Nedd4 is unlikely to function in axon guidance at the midline.