
Thesis Format
Integrated Article
Degree
Master of Science
Program
Biochemistry
Supervisor
Heinemann, Ilka U.
Abstract
Charcot-Marie-Tooth disease (CMT) is the most commonly inherited peripheral neuropathy, with mutations in over 150 genes. The underlying pathology of CMT primarily involves either myelin sheath degradation or axonal damage, with no unifying molecular mechanism of disease. Notably, mutations in aminoacyl-tRNA synthetases have been linked to CMT2, with histidyl-tRNA synthetase (HARS) specifically implicated in CMT2W. These enzymes play a crucial role in charging tRNAs with their corresponding amino acids, facilitating peptide synthesis during mRNA translation. Here, I use a humanized HARS yeast model and protein biochemistry to investigate the molecular mechanisms associated with the disease-causing HARS variants V133F, Y330C, and Y138H, identifying mistranslation and impaired dimerization as disease-causing mechanisms in HARS-related CMT. I also demonstrate the feasibility of tRNAHis supplementation as a therapeutic with the rescue of mistranslation in V133F and Y330C and expand the potential use of histidine as a therapeutic option to the Y138H variant.
Summary for Lay Audience
Charcot Marie Tooth (CMT) hereditary neuropathies are a group of diseases characterized by peripheral motor and sensory nerve problems, usually leading to muscle death with no current disease specific treatment options. CMT affects 2.6 million individuals globally and is caused by mutations in various genes. Aminoacyl-tRNA synthetases (aaRSs), which are essential for production of new proteins in cells, are a hotspot for CMT variants with 59 unique mutations in six different aaRSs identified as causal for CMT. Histidyl tRNA-synthetase (HARS), needed for incorporation of histidine in new proteins, has 11 unique CMT disease-associated mutations. Here, I present a case study, characterizing the Y138H HARS variant and providing evidence to support the use of histidine supplementation as a therapeutic option by using biochemical assays and a yeast model of human HARS disease. Yeast is a popular model system for human disease as many of the basic cell functions are conserved between yeast and humans. Additionally, I show incorrect protein synthesis, known as mistranslation, as a disease-causing mechanism in HARS variants V133F and Y330C. The disease traits in this model were rescued with the addition of tRNAHis, the molecule required for accurate histidine incorporation in newly made proteins, showing the feasibility of a therapeutic that increases the amount of a naturally occurring RNA in the cell. Several studies show that prolonged, high dose histidine is a safe nutritional supplement, and RNA has been used in other medical interventions such as vaccines. The results of this research may apply broadly across populations to help patients who are currently limited to therapies targeted at alleviating symptoms, rather than addressing the root cause of the disease.
Recommended Citation
Wilhelm, Sarah DP, "Exploring the Molecular Landscape of HARS-Associated Charcot-Marie-Tooth Disease: Disease Mechanisms and Therapeutic Interventions" (2024). Electronic Thesis and Dissertation Repository. 10612.
https://ir.lib.uwo.ca/etd/10612