tRNA overexpression rescues peripheral neuropathy caused by mutations in tRNA synthetase.

Heterozygous mutations in six transfer RNA (tRNA) synthetase genes cause Charcot-Marie-Tooth (CMT) peripheral neuropathy. CMT mutant tRNA synthetases inhibit protein synthesis by an unknown mechanism. We found that CMT mutant glycyl-tRNA synthetases bound tRNA but failed to release it, resulting in tRNA sequestration. This sequestration potentially depleted the cellular tRNA pool, leading to insufficient glycyl-tRNA supply to the ribosome. Accordingly, we found ribosome stalling at glycine codons and activation of the integrated stress response (ISR) in affected motor neurons. Moreover, transgenic overexpression of tRNA rescued protein synthesis, peripheral neuropathy, and ISR activation in and mouse CMT disease type 2D (CMT2D) models. Conversely, inactivation of the ribosome rescue factor GTPBP2 exacerbated peripheral neuropathy. Our findings suggest a molecular mechanism for CMT2D, and elevating tRNA levels may thus have therapeutic potential.