Tyrosyl-tRNA sequestration triggers tyrosyl-tRNA synthetase-associated peripheral neuropathy.

Abstract

Mono-allelic mutations in seven cytosolic aminoacyl-tRNA synthetase genes cause Charcot-Marie-Tooth (CMT) peripheral neuropathy. Here, we report that tyrosyl-tRNA (tRNATyr) sequestration by CMT-mutant tyrosyl-tRNA synthetase (TyrRS) is the molecular root cause of CMT-YARS1. tRNATyr sequestration depletes the cellular free tRNATyr pool, leading to insufficient tyrosyl-tRNATyr production and ribosome stalling at tyrosine codons. In three Drosophila CMT-YARS1 models, transgenic overexpression of tRNATyr rescued peripheral neuropathy phenotypes and defective mRNA translation. We provide biochemical evidence for tRNATyr sequestration by the three CMT-TyrRS variants expressed in the Drosophila models and ribosome profiling revealed selective ribosome pausing at the two tyrosine codons. In the Yars1E196K mouse model, adeno-associated virus serotype 9 (AAV9)-mediated overexpression of tRNATyr-but not wild-type TyrRS protein-fully rescued motor performance deficits, reduced nerve conduction velocity and reduced motor axon calibre. Furthermore, AAV9-tRNATyr gene therapy prevented activation of the integrated stress response in spinal motor neurons, indicating resolution of ribosome stalling. Thus, elevating tRNATyr levels constitutes a novel therapeutic approach for CMT-YARS1.