Electronic Thesis and Dissertation Repository

Thesis Format



Master of Science




Heinemann, Ilka U.


tRNAs are the adapter molecules involved in translating the genetic code into functional protein in a living cell. tRNAs are charged with their cognate amino acids - by aminoacyl-tRNA synthetases (aaRS or ARS) - which are then transferred to a growing peptide in a process called mRNA translation. The efficiency of translation is dependent on the ratio of ARS enzymes to their cognate tRNAs and the availability of correctly amino acylated tRNAs. Disruptions of this process, caused by mutations in ARS genes, in particular, have been linked to complex inherited diseases. USH3B syndrome, a recessively inherited disorder among consanguineous families in Canada, was recently associated with a mutation (Y454S) in human histidyl-tRNA synthetase gene. Here, I create a yeast model of USH3B syndrome. I aim to investigate the pathological impact of Y454S, in hope to expand the genetic and clinical spectrum of ARS-related human diseases.

Summary for Lay Audience

Alterations in the human genome have been associated with complex human disorders. In 2012, an inherited disorder named Usher Syndrome type 3B (USH3B syndrome) was reported among families in Canada. USH3B syndrome is a combined deafness and blindness disorder. Patients of USH3B syndrome experience hallucinations during acute illness and fevers. The genetic variation (Y454S) underlying USH3B syndrome is located in a histidyl tRNA synthetase gene (HARS). HARS is an enzyme that is essentially involved in the cellular synthesis of proteins. A recent study, on USH3B patients’ cells, has shown that the primary function of HARS seems unaffected by the variation, unless temperatures were elevated to 43°C (resembles fever). It was suggested that the variation results in a temperature sensitive HARS enzyme. In this study, I investigated the Y454S variation in HARS, by creating a yeast model for the disease. Yeast is one of the simplest eukaryotic organisms that shares many essential cellular processes with humans – which makes it a popular model organism for human diseases. I replaced yeast HARS gene with Y454S human HARS, and emulated fever by exposing the cells to heat shock and stress conditions. Furthermore, I carried out biochemical experiments to investigate whether the variation in HARS leads to reduced protein production and/or accumulation of faulty proteins. In my study, I set an experimental outline for using yeast as a model for human disorders, in hope to expand the genetic understanding of complex human diseases.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.