Division of Medical Genetics and Genomics, The Children's Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
Institute of Genetics, Zhejiang University and Department of Human Genetics, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, China.
Nucleic Acids Res. 2018 Nov 16;46(20):10930-10945. doi: 10.1093/nar/gky758.
Mtu1(Trmu) is a highly conserved tRNA modifying enzyme responsible for the biosynthesis of τm5s2U at the wobble position of tRNAGln, tRNAGlu and tRNALys. Our previous investigations showed that MTU1 mutation modulated the phenotypic manifestation of deafness-associated mitochondrial 12S rRNA mutation. However, the pathophysiology of MTU1 deficiency remains poorly understood. Using the mtu1 knock-out zebrafish generated by CRISPR/Cas9 system, we demonstrated the abolished 2-thiouridine modification of U34 of mitochondrial tRNALys, tRNAGlu and tRNAGln in the mtu1 knock-out zebrafish. The elimination of this post-transcriptional modification mediated mitochondrial tRNA metabolisms, causing the global decreases in the levels of mitochondrial tRNAs. The aberrant mitochondrial tRNA metabolisms led to the impairment of mitochondrial translation, respiratory deficiencies and reductions of mitochondrial ATP production. These mitochondria dysfunctions caused the defects in hearing organs. Strikingly, mtu1-/- mutant zebrafish displayed the abnormal startle response and swimming behaviors, significant decreases in the sizes of saccular otolith and numbers of hair cells in the auditory and vestibular organs. Furthermore, mtu1-/- mutant zebrafish exhibited the significant reductions in the hair bundle densities in utricle, saccule and lagena. Therefore, our findings may provide new insights into the pathophysiology of deafness, which was manifested by the deficient modifications at wobble position of mitochondrial tRNAs.
Mtu1(Trmu) 是一种高度保守的 tRNA 修饰酶，负责 tRNAGln、tRNAGlu 和 tRNALys 中 wobble 位置的 τm5s2U 的生物合成。我们之前的研究表明，MTU1 突变调节了与耳聋相关的线粒体 12S rRNA 突变的表型表现。然而，MTU1 缺乏的病理生理学仍知之甚少。我们使用 CRISPR/Cas9 系统生成的 mtu1 敲除斑马鱼，证明了 mtu1 敲除斑马鱼中线粒体 tRNALys、tRNAGlu 和 tRNAGln 的 U34 2-硫代尿苷修饰被废除。这种转录后修饰的消除介导了线粒体 tRNA 代谢，导致线粒体 tRNA 水平的全面降低。异常的线粒体 tRNA 代谢导致线粒体翻译受损、呼吸缺陷和线粒体 ATP 产生减少。这些线粒体功能障碍导致听力器官缺陷。引人注目的是，mtu1-/- 突变斑马鱼表现出异常的惊跳反应和游泳行为、囊斑耳石的大小显著减小以及听觉和前庭器官毛细胞数量减少。此外，mtu1-/- 突变斑马鱼在耳石、囊斑和壶腹中的毛束密度显著减少。因此，我们的发现可能为耳聋的病理生理学提供新的见解，其表现为线粒体 tRNA 的 wobble 位置修饰不足。
