Improving the diagnostic outcomes of patients with mitochondrial disease

Researcher

Project Details

Genetic disorders affecting mitochondrial OXPHOS constitute the most common form of inherited metabolic disease, affecting ~1/5000 births. There are few, if any proven treatments. The diagnosis rate for mitochondrial disease is only ~60% and those lucky enough to receive a molecular diagnosis often wait months or years. With our collaborator Prof. David Thorburn at the Murdoch Children's Research Institute, our lab is developing the use of quantitative proteomics to complement the existing tools in the diagnosis of mitochondrial disease.

For example, we and our collaborators recently identified a number of patients with mutations in the gene encoding mitochondrial ribosome subunit MRPS34 (Lake et al., 2017 Am J Hum Genet). The mitochondrial ribosome is required for the synthesis of all 13 mtDNA encoded subunits of the OXPHOS system. Using quantitative proteomics tools that we developed, we could not only identify MRPS34 as the most affected mitochondrial protein in the patient (Figure 1A), but also show the downstream effect on the mitochondrial OXPHOS system (Figure 1B) and the impact of the mutation on the assembly of the mitochondrial ribosome (Figure. 2).

Volcano plot depicting results following quantitative proteomics analysis of fibroblasts from a patient with defects in MRPS34, a protein found in the small  subunit of the mitochondrial ribosome
Figure 1: (A) Volcano plot depicting results following quantitative proteomics analysis of fibroblasts from a patient (Patient 3) with defects in MRPS34, a protein found in the small subunit of the mitochondrial ribosome. Other proteins found in the small subunit (red) and subunits of the OXPHOS machinery (blue) were also found to be reduced in the patient cells relative to controls, whereas proteins found in the large mitochondrial ribosome subunit (yellow) were unaffected. (B) Comparison between the results of traditional enzymatic assays for OXPHOS complex activity and data derived from the proteomics experiment in A. The enzymatic activity for each complex strongly correlated with the turnover of subunits.

Figure 2: Mapping of proteomics data from Figure 1A to the structure of the mitochondrial ribosome. Proteins found in the the small mitoribosome subunit were severely depleted in the patient cells relative to controls (as depicted by blue colours), whereas proteins of the large subunit were unaffected. The mutated subunit is indicated in yellow. PDB: 3J9M.

This project employs extensive quantitative proteomics tools, as well as mammalian cell culture of patient and gene-edited hESC cells, bioinformatics and computational biology, and metabolic and enzymatic measurements. Discoveries are complemented by traditional biochemical and molecular biology studies to determine the roles of affected proteins in mitochondrial function.

Research Group

Stroud laboratory: Mitochondrial Systems Biology



Faculty Research Themes

Child Health

School Research Themes

Cardio-Respiratory, Systems Biology, Molecular Mechanisms of Disease



Key Contact

For further information about this research, please contact the research group leader.

Department / Centre

Biochemistry and Molecular Biology

Unit / Centre

Stroud laboratory: Mitochondrial Systems Biology


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