MRC PhD student

Level of study: MSc

Title: Differential expression of genes in clinical strains of Mycobacterium Tuberculosis in response to isoniazid

Currently INH forms part of the first line anti-tuberculosis therapy, but molecular mechanism of INH action and resistance still remains poorly defined. INH enters tubercle bacilli as a prodrug and requires activation to its active form by catalase peroxidase encoding gene, katG. Loss of catalase peroxidase due to gene mutations or whole katG deletion is one of the primary mechanisms conferring resistance to INH. In addition four other genes (inhA, KasA, ndh and ahpC) are associated with INH resistance. However, mutations in these five genes are absent in 25-30% of INH resistant clinical isolates collected from various geographical regions. These results imply that other genes or mechanisms are involved in INH resistance.

Aim
Identification of differentially expressed genes in Mycobacterium tuberculosis in response to INH exposure

Methodology

1. An H37Rv, Mycobacterium tuberculosis Beijing cluster 208 fully susceptible and INH mono-resistant strains will be selected from an existing strain bank at the University of Stellenbosch
2. Candidate genes will be selected based on literature search and bioinformatics.
3. These genes will be used to assess differential gene expression using QRT-PCR with and without the bacterium being exposed to sub-lethal INH
4. The strains will be further assessed for differential protein expression using Proteomics (orbitrap) with and without sub-lethal INH induction
5. The data will be combined with previously identified differential expressed genes from the same set of samples to construct pathways that lead to INH resistance in Mycobacterium tuberculosis.

Supervisors: Dr Rabia Johnson and Prof Tommie Victor
Study Institution: DST/NRF Center of Excellence in Biomedical Tuberculosis Research, Division of Molecular Biology and Human Genetics, Department of Biomedical Science, Faculty of health science, Stellenbosch University
MRC Unit: Centre for Molecular and Cellular Biology