Determining ribosome-associated mRNA in motor neurons in pre-disease onset GarsC201R mice

To determine transcriptome changes in pre-disease onset motor neurons induced by the GarsC201R mutation. How mutations in broadly expressed housekeeping genes lead to neurodegeneration in specific cell types remains unclear. Mutations in ubiquitously expressed tRNA synthetase genes cause axonal peripheral neuropathy, accounting for at least six forms of Charcot-Marie-Tooth disease. Genetic evidence in mouse and Drosophila models suggests a neomorphic gain-of-function mechanism. Here, we use in vivo, cell-type-specific transcriptional and translational profiling of affected peripheral neurons to show that mutant tRNA synthetases impair translation and activate the integrated stress response (ISR) through the sensor kinase, GCN2. The chronic activation of the ISR contributes to the pathophysiology, and genetic deletion of Gcn2 alleviates the peripheral neuropathy. The activation of GCN2 by tRNA synthetase mutations indicates their neomorphic activity is still related to translation and suggests inhibiting GCN2 or the ISR as a therapeutic strategy. Overall design: RiboTagging was performed on spinal cords from 2 week old HARPL22;ChAT-Cre;Gars+/+ or GarsC201R/+ and corresponding negative controls (no Cre) and differential expression analyis was run.