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Charcot-Marie-Tooth (CMT) neuropathies are collectively the most common hereditary neurological condition and a major health burden for society. Dominant mutations in the gene GARS, encoding the ubiquitous enzyme, glycyl-tRNA synthetase (GlyRS), cause peripheral nerve degeneration and lead to CMT disease type 2D. This genetic disorder exemplifies a recurring motif in neurodegeneration, whereby mutations in essential, widely expressed genes have selective deleterious consequences for the nervous system. Here, using novel Drosophila models, we show a potential solution to this phenomenon. Ubiquitous expression of mutant GlyRS leads to motor deficits, progressive neuromuscular junction (NMJ) denervation and pre-synaptic build-up of mutant GlyRS. Intriguingly, neuronal toxicity is, at least in part, non-cell autonomous, as expression of mutant GlyRS in mesoderm or muscle alone results in similar pathology. This mutant GlyRS toxic gain-of-function, which is WHEP domain-dependent, coincides with abnormal NMJ assembly, leading to synaptic degeneration, and, ultimately, reduced viability. Our findings suggest that mutant GlyRS gains access to ectopic sub-compartments of the motor neuron, providing a possible explanation for the selective neuropathology caused by mutations in a widely expressed gene.

Original publication

DOI

10.1093/hmg/ddv176

Type

Journal article

Journal

Hum Mol Genet

Publication Date

01/08/2015

Volume

24

Pages

4397 - 4406

Keywords

Animals, Charcot-Marie-Tooth Disease, Disease Models, Animal, Drosophila melanogaster, Gene Expression Regulation, Glycine-tRNA Ligase, Humans, Mushroom Bodies, Mutation, Nerve Degeneration, Neuromuscular Junction, Olfactory Bulb, Peripheral Nerves