Dominant mutations in the tyrosyl-tRNA synthetase gene recapitulate in **Drosophila** features of human CharcotMarieTooth neuropathy
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences . Biomedical Sciences
Proceedings of the National Academy of Sciences of the United States of America. - Washington, D.C.
, p. 11782-11787
University of Antwerp
Dominant-intermediate CharcotMarieTooth neuropathy (DI-CMT) is characterized by axonal degeneration and demyelination of peripheral motor and sensory neurons. Three dominant mutations in the YARS gene, encoding tyrosyl-tRNA synthetase (TyrRS), have so far been associated with DI-CMT type C. The molecular mechanisms through which mutations in YARS lead to peripheral neuropathy are currently unknown, and animal models for DI-CMTC are not yet available. Here, we report the generation of a Drosophila model of DI-CMTC: expression of the 3 mutantbut not wild typeTyrRS in Drosophila recapitulates several hallmarks of the human disease, including a progressive deficit in motor performance, electrophysiological evidence of neuronal dysfunction and morphological signs of axonal degeneration. Not only ubiquitous, but also neuron-specific expression of mutant TyrRS, induces these phenotypes, indicating that the mutant enzyme has cell-autonomous effects in neurons. Furthermore, biochemical and genetic complementation experiments revealed that loss of enzymatic activity is not a common feature of DI-CMTC-associated mutations. Thus, the DI-CMTC phenotype is not due to haploinsufficiency of aminoacylation activity, but most likely to a gain-of-function alteration of the mutant TyrRS or interference with an unknown function of the WT protein. Our results also suggest that the molecular pathways leading to mutant TyrRS-associated neurodegeneration are conserved from flies to humans.