Author(s): Sheila Marte, University of Michigan; Anthony Antonellis, University of Michigan //

ABSTRACT: Aminoacyl-tRNA synthetases (ARSs) are essential enzymes required to charge tRNA molecules to cognate amino acids in the cytoplasm and mitochondria. Although ARSs are essential and ubiquitously expressed, loss-of-function (LOF) missense mutations in five dimeric ARS enzymes have been associated with dominant peripheral neuropathy (also known as Charcot-Marie-Tooth disease [CMT]). CMT is a genetically and clinically heterogeneous inherited peripheral neuropathy characterized by the progressive loss of motor and sensory function. Mutations in glycyl-tRNA synthetase (GARS1) have been associated with distinct clinical phenotypes where individuals can present with later-onset CMT or infantile spinal muscular atrophy. The mechanism by which mutations in GARS1 lead to distinct clinical phenotypes is currently unclear. Since all five implicated ARSs function as dimers and since CMT-associated ARS variants all cause a loss-of-function effect, we propose the possibility of a dominant-negative mechanism. To test dominant-negative effects of pathogenic glycyl-tRNA synthetase (GARS1) variants, we will develop a humanized yeast model and test GARS1 mutations for the ability to repress a wild-type copy of GARS1. To better understand the distinct clinical phenotypes, we will assess the dominant toxicity of a series of pathogenic GARS1 alleles to determine if toxicity in our yeast model correlates with disease severity. Finally, we will identify pathways that, when manipulated, improve GARS1 function by performing experimental evolution and gain-of-function studies using a hypomorphic allele and yeast growth assays. Here, we will present preliminary data on development of our humanized model and on initial assessments of the dominant toxicity of pathogenic GARS1 alleles. These studies will provide insight into the pathogenic mechanism of ARS-related CMT and aid in the development of therapeutics.

Source of Funding: NIH