Department of Molecular Biology and Biochemistry, and Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, BC, Canada.
Department of Cell, Developmental, and Integrative Biology, University of Alabama at Birmingham Medical School, Birmingham, AL, USA.
EMBO Rep. 2018 Dec;19(12). doi: 10.15252/embr.201845862. Epub 2018 Nov 14.
Genetic disorders caused by cilia dysfunction, termed ciliopathies, frequently involve the intraflagellar transport (IFT) system. Mutations in IFT subunits-including IFT-dynein motor DYNC2H1-impair ciliary structures and Hedgehog signalling, typically leading to "skeletal" ciliopathies such as Jeune asphyxiating thoracic dystrophy. Intriguingly, IFT gene mutations also cause eye, kidney and brain ciliopathies often linked to defects in the transition zone (TZ), a ciliary gate implicated in Hedgehog signalling. Here, we identify a temperature-sensitive () IFT-dynein mutant (; human DYNC2H1) and use it to show a role for retrograde IFT in anterograde transport and ciliary maintenance. Unexpectedly, correct TZ assembly and gating function for periciliary proteins also require IFT-dynein. Using the reversibility of the novel -IFT-dynein, we show that restoring IFT in adults (post-developmentally) reverses defects in ciliary structure, TZ protein localisation and ciliary gating. Notably, this ability to reverse TZ defects declines as animals age. Together, our findings reveal a previously unknown role for IFT in TZ assembly in metazoans, providing new insights into the pathomechanism and potential phenotypic overlap between IFT- and TZ-associated ciliopathies.
由纤毛功能障碍引起的遗传疾病，称为纤毛病，通常涉及内鞭毛运输（IFT）系统。IFT 亚基（包括 IFT-动力蛋白 DYNC2H1）的突变会破坏纤毛结构和 Hedgehog 信号传导，通常导致“骨骼”纤毛病，如 Jeune 窒息性胸肌营养不良。有趣的是，IFT 基因突变也会导致眼睛、肾脏和大脑纤毛病，这些纤毛病通常与过渡区（TZ）缺陷有关，TZ 是 Hedgehog 信号传导中涉及的纤毛门。在这里，我们鉴定了一个温度敏感的（）IFT-动力蛋白突变体（；人类 DYNC2H1），并利用它来表明逆行 IFT 在顺行运输和纤毛维持中的作用。出乎意料的是，正确的 TZ 组装和边缘蛋白的门控功能也需要 IFT-动力蛋白。利用新型 IFT-动力蛋白的可逆性，我们表明在成年期（发育后）恢复 IFT 可以逆转纤毛结构、TZ 蛋白定位和纤毛门控的缺陷。值得注意的是，这种逆转 TZ 缺陷的能力随着动物年龄的增长而下降。总之，我们的研究结果揭示了 IFT 在后生动物 TZ 组装中的一个先前未知的作用，为 IFT 和 TZ 相关纤毛病的发病机制和潜在表型重叠提供了新的见解。
