title: Functional analyses of glycyl-tRNA synthetase mutations suggest a key role for tRNA-charging enzymes in peripheral axons.
abstract: Charcot-Marie-Tooth disease type 2D (CMT2D) and distal spinal muscular atrophy type V (dSMA-V) are axonal neuropathies characterized by a phenotype that is more severe in the upper extremities. We previously implicated mutations in the gene encoding glycyl-tRNA synthetase (GARS) as the cause of CMT2D and dSMA-V. GARS is a member of the family of aminoacyl-tRNA synthetases responsible for charging tRNA with cognate amino acids; GARS ligates glycine to tRNA(Gly). Here, we present functional analyses of disease-associated GARS mutations and show that there are not any significant mutation-associated changes in GARS expression levels; that the majority of identified GARS mutations modeled in yeast severely impair viability; and that, in most cases, mutant GARS protein mislocalizes in neuronal cells. Indeed, four of the five mutations studied show loss-of-function features in at least one assay, suggesting that tRNA-charging deficits play a role in disease pathogenesis. Finally, we detected endogenous GARS-associated granules in the neurite projections of cultured neurons and in the peripheral nerve axons of normal human tissue. These data are particularly important in light of the recent identification of CMT-associated mutations in another tRNA synthetase gene [YARS (tyrosyl-tRNA synthetase gene)]. Together, these findings suggest that tRNA-charging enzymes play a key role in maintaining peripheral axons.
authors.affiliation: Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Antonellis
authors.forename: Shih-Queen
authors.initials: SQ
authors.lastname: Lee-Lin
authors.forename: Amy
authors.initials: A
authors.lastname: Wasterlain
authors.forename: Paul
authors.initials: P
authors.lastname: Leo
authors.forename: Martha
authors.initials: M
authors.lastname: Quezado
authors.forename: Lev G
authors.initials: LG
authors.lastname: Goldfarb
authors.forename: Kyungjae
authors.initials: K
authors.lastname: Myung
authors.forename: Shawn
authors.initials: S
authors.lastname: Burgess
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Fischbeck
authors.forename: Eric D
authors.initials: ED
authors.lastname: Green
mesh_terms: D000818:Animals; D001369:Axons / Q000201:enzymology*; D019556:COS Cells; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002607:Charcot-Marie-Tooth Disease / Q000201:enzymology / Q000235:genetics; D002522:Chlorocebus aethiops; D005786:Gene Expression Regulation / Q000502:physiology; D006032:Glycine-tRNA Ligase / Q000235:genetics* / Q000502:physiology; D006801:Humans; D051379:Mice; D009154:Mutation; D010525:Peripheral Nerves / Q000201:enzymology*; D046249:Transfer RNA Aminoacylation / Q000502:physiology*
chemical_list: D006032:Glycine-tRNA Ligase