title: Dimerization is required for GARS-mediated neurotoxicity in dominant CMT disease.
abstract: Charcot-Marie-Tooth (CMT) disease is a genetically heterogeneous group of peripheral neuropathies. Mutations in several aminoacyl-tRNA synthetase (ARS) genes have been implicated in inherited CMT disease. There are 12 reported CMT-causing mutations dispersed throughout the primary sequence of the human glycyl-tRNA synthetase (GARS). While there is strong genetic evidence linking GARS mutations to CMT disease, the molecular pathology underlying the neuromuscular and sensory phenotypes is still not fully understood. In particular, it is unclear whether the mutations result in a toxic gain of function, a partial loss of activity related to translation, or a combination of these mechanisms. We identified a zebrafish allele of gars (gars(s266)). Homozygous mutant embryos carry a C->A transversion, that changes a threonine to a lysine, in a residue next to a CMT-associated human mutation. We show that the neuromuscular phenotype observed in animals homozygous for T209K Gars (T130K in GARS) is due to a loss of dimerization of the mutated protein. Furthermore, we show that the loss of function, dimer-deficient and human disease-associated G319R Gars (G240R in GARS) mutant protein is unable to rescue the above phenotype. Finally, we demonstrate that another human disease-associated mutant G605R Gars (G526 in GARS) dimerizes with the remaining wild-type protein in animals heterozygous for the T209K Gars and reduces the function enough to elicit a neuromuscular phenotype. Our data indicate that dimerization is required for the dominant neurotoxicity of disease-associated GARS mutations and provide a rapid, tractable model for studying newly identified GARS variants for a role in human disease.
authors.affiliation: Developmental Biology, Biomedical Research Foundation Academy of Athens, Soranou Ephessiou 4, 11527 Athens, Greece, Medical School, University of Crete, Greece.
authors.forename: Nikos
authors.initials: N
authors.lastname: Malissovas
authors.affiliation: Cellular and Molecular Biology Program, Medical Scientist Training Program.
authors.forename: Laurie B
authors.initials: LB
authors.lastname: Griffin
authors.affiliation: Cellular and Molecular Biology Program, Department of Human Genetics, and Department of Neurology, University of Michigan Medical School, Ann Arbor, MI, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Antonellis
authors.affiliation: Developmental Biology, Biomedical Research Foundation Academy of Athens, Soranou Ephessiou 4, 11527 Athens, Greece, dbeis@bioacademy.gr.
authors.forename: Dimitris
authors.initials: D
authors.lastname: Beis
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002607:Charcot-Marie-Tooth Disease / Q000235:genetics / Q000473:pathology*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation; D006032:Glycine-tRNA Ligase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D010641:Phenotype; D055503:Protein Multimerization; D015027:Zebrafish / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D029961:Zebrafish Proteins; D006032:Glycine-tRNA Ligase