Institute of Evolution and Marine Biodiversity, College of Marine Life Science, Ocean University of China, Qingdao, China.
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China.
FASEB J. 2018 Jul;32(7):3984-3992. doi: 10.1096/fj.201701359R. Epub 2018 Feb 22.
Radial spokes are structurally conserved, macromolecular complexes that are essential for the motility of 9 + 2 motile cilia. In Chlamydomonas species, mutations in radial spoke proteins result in ciliary motility defects. However, little is known about the function of radial spoke proteins during embryonic development. Here, we investigated the role of a novel radial spoke protein, leucine-rich repeat containing protein 23 (Lrrc23), during zebrafish embryonic development. Mutations in lrrc23 resulted in a selective otolith formation defect during early ear development. Similar otolith defects were also present in the radial spoke head 3 homolog ( rsph3) and radial spoke head 4 homolog A ( rsph4a) radial spoke mutants. Notably, the radial spoke protein mutations specifically affected ciliary motility in the otic vesicle (OV), whereas motile cilia in other organs functioned normally. Via high-speed video microscopy, we found that motile cilia formation was stochastic and transient in the OV. Importantly, all the motile cilia in the OV beat circularly, in contrast to the planar beating pattern of typical 9 + 2 motile cilia. We identified the key time frame for motile cilia formation during OV development. Finally, we showed that the functions of radial spoke proteins were conserved between zebrafish and Tetrahymena. Together, our results suggest that radial spoke proteins are essential for ciliary motility in the OV and that radial spoke-regulated OV motile cilia represent a unique type of cilia during early zebrafish embryonic development.-Han, X., Xie, H., Wang, Y., Zhao, C. Radial spoke proteins regulate otolith formation during early zebrafish development.
辐条是结构保守的、大分子复合物，对于 9 + 2 运动纤毛的运动是必不可少的。在衣藻属物种中，辐条蛋白的突变导致纤毛运动缺陷。然而，对于辐条蛋白在胚胎发育过程中的功能知之甚少。在这里，我们研究了一种新型辐条蛋白，富含亮氨酸重复蛋白 23（Lrrc23），在斑马鱼胚胎发育过程中的作用。lrrc23 的突变导致早期耳发育过程中选择性耳石形成缺陷。在径向 spoke 头 3 同源物（rsph3）和径向 spoke 头 4 同源物 A（rsph4a）径向 spoke 突变体中也存在类似的耳石缺陷。值得注意的是，径向 spoke 蛋白突变特异性影响卵囊（OV）中的纤毛运动，而其他器官中的运动纤毛正常发挥功能。通过高速视频显微镜，我们发现 OV 中的运动纤毛形成是随机和短暂的。重要的是，OV 中的所有运动纤毛都是圆形的，与典型的 9 + 2 运动纤毛的平面拍打模式形成对比。我们确定了 OV 发育过程中运动纤毛形成的关键时间框架。最后，我们表明，径向 spoke 蛋白在斑马鱼和四膜虫之间的功能是保守的。总之，我们的结果表明，径向 spoke 蛋白对于 OV 中的纤毛运动是必不可少的，并且径向 spoke 调节的 OV 运动纤毛代表了早期斑马鱼胚胎发育过程中一种独特的纤毛类型。
