Recent studies have revealed unexpected connections between the mammalian Hedgehog (Hh) signal transduction pathway and the primary cilium, a microtubule-based organelle that protrudes from the surface of most vertebrate cells. Intraflagellar transport proteins, which are required for the construction of cilia, are essential for all responses to mammalian Hh proteins, and proteins required for Hh signal transduction are enriched in primary cilia. The phenotypes of different mouse mutants that affect ciliary proteins suggest that cilia may act as processive machines that organize sequential steps in the Hh signal transduction pathway. Cilia on vertebrate cells are likely to be important in additional developmental signaling pathways and are required for PDGF receptor alpha signaling in cultured fibroblasts. Cilia are not essential for either canonical or noncanonical Wnt signaling, although cell-type-specific modulation of cilia components may link cilia and Wnt signaling in some tissues. Because ciliogenesis in invertebrates is limited to a very small number of specialized cell types, the role of cilia in developmental signaling pathways is likely a uniquely vertebrate phenomenon.

中文翻译：

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纤毛和发育信号。

最近的研究表明，哺乳动物的刺猬（Hh）信号转导途径与初级纤毛之间存在意想不到的联系，纤毛是一种从大多数脊椎动物细胞表面突出的基于微管的细胞器。纤毛构建所需的鞭毛内转运蛋白对于对哺乳动物Hh蛋白的所有应答都是必不可少的，Hh信号转导所需的蛋白富含初级纤毛。影响纤毛蛋白的不同小鼠突变体的表型表明纤毛可以充当组织Hh信号转导途径中连续步骤的过程性机器。脊椎动物细胞上的纤毛可能在其他发育信号途径中很重要，并且是培养成纤维细胞中PDGF受体α信号传导所必需的。尽管纤毛成分的细胞类型特异性调节可能会在某些组织中链接纤毛和Wnt信号传导，纤毛对于规范的或非规范的Wnt信号传导并不是必需的。由于无脊椎动物的纤毛发生仅限于极少数的特殊细胞类型，纤毛在发育信号通路中的作用可能是独特的脊椎动物现象。