Rajagopalan Vidyalakshmi, Subramanian Aswati, Wilkes David E, Pennock David G, Asai David J
Department of Biology, Harvey Mudd College, Claremont, CA 91711, USA.
Mol Biol Cell. 2009 Jan;20(2):708-20. doi: 10.1091/mbc.e08-07-0746. Epub 2008 Nov 19.
Eukaryotic cilia and flagella are assembled and maintained by the bidirectional intraflagellar transport (IFT). Studies in alga, nematode, and mouse have shown that the heavy chain (Dyh2) and the light intermediate chain (D2LIC) of the cytoplasmic dynein-2 complex are essential for retrograde intraflagellar transport. In these organisms, disruption of either dynein-2 component results in short cilia/flagella with bulbous tips in which excess IFT particles have accumulated. In Tetrahymena, the expression of the DYH2 and D2LIC genes increases during reciliation, consistent with their roles in IFT. However, the targeted elimination of either DYH2 or D2LIC gene resulted in only a mild phenotype. Both knockout cell lines assembled motile cilia, but the cilia were of more variable lengths and less numerous than wild-type controls. Electron microscopy revealed normally shaped cilia with no swelling and no obvious accumulations of material in the distal ciliary tip. These results demonstrate that dynein-2 contributes to the regulation of ciliary length but is not required for ciliogenesis in Tetrahymena.
真核生物的纤毛和鞭毛由双向的鞭毛内运输（IFT）组装并维持。对藻类、线虫和小鼠的研究表明，胞质动力蛋白-2复合体的重链（Dyh2）和轻中间链（D2LIC）对于逆行鞭毛内运输至关重要。在这些生物体中，动力蛋白-2的任何一个组分受到破坏都会导致纤毛/鞭毛变短，其顶端呈球状，其中积累了过量的IFT颗粒。在四膜虫中，DYH2和D2LIC基因的表达在纤毛形成过程中增加，这与其在IFT中的作用一致。然而，靶向消除DYH2或D2LIC基因仅导致轻微的表型。两种基因敲除细胞系都组装了能动的纤毛，但这些纤毛的长度变化更大，数量也比野生型对照少。电子显微镜显示纤毛形状正常，没有肿胀，在纤毛远端顶端也没有明显的物质积累。这些结果表明，动力蛋白-2有助于调节纤毛长度，但在四膜虫的纤毛发生过程中并非必需。
