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Systems biology of mitochondrial diseases

Investigators: Professor Aleksandra Filipovska, Dr Stefan Siira Project description  This project will focus on new and cutting-edge development of

Interorganelle phospholipid communication, a house not so divided

The presence of membrane-bound organelles with specific functions is one of the main hallmarks of eukaryotic cells. Organelle membranes are composed of specific lipids that govern their function and interorganelle communication. Discoveries in cell biology using imaging and omic technologies have revealed the mechanisms that drive membrane remodeling, organelle contact sites, and metabolite exchange.

Quantitative subcellular reconstruction reveals a lipid mediated inter-organelle biogenesis network

The structures and functions of organelles in cells depend on each other but have not been systematically explored. We established stable knockout cell lines of peroxisomal, Golgi and endoplasmic reticulum genes identified in a whole-genome CRISPR knockout screen for inducers of mitochondrial biogenesis stress, showing that defects in peroxisome, Golgi and endoplasmic reticulum metabolism disrupt mitochondrial structure and function. 

A common genetic variant of a mitochondrial RNA processing enzyme predisposes to insulin resistance

Mitochondrial energy metabolism plays an important role in the pathophysiology of insulin resistance. Recently, a missense N437S variant was identified in the MRPP3 gene, which encodes a mitochondrial RNA processing enzyme within the RNase P complex, with predicted impact on metabolism. We used CRISPR-Cas9 genome editing to introduce this variant into the mouse Mrpp3 gene and show that the variant causes insulin resistance on a high-fat diet.

The mitochondrial single-stranded DNA binding protein is essential for initiation of mtDNA replication

We report a role for the mitochondrial single-stranded DNA binding protein (mtSSB) in regulating mitochondrial DNA (mtDNA) replication initiation in mammalian mitochondria. Transcription from the light-strand promoter (LSP) is required both for gene expression and for generating the RNA primers needed for initiation of mtDNA synthesis.

Stepwise maturation of the peptidyl transferase region of human mitoribosomes

Mitochondrial ribosomes are specialized for the synthesis of membrane proteins responsible for oxidative phosphorylation. Mammalian mitoribosomes have diverged considerably from the ancestral bacterial ribosomes and feature dramatically reduced ribosomal RNAs. The structural basis of the mammalian mitochondrial ribosome assembly is currently not well understood. Here we present eight distinct assembly intermediates of the human large mitoribosomal subunit involving seven assembly factors.

Mitochondrial Medicine and Biology

Mitochondrial diseases are devastating disorders for which there are no cures or effective treatments. Our project will focus on the prevention of mitochondrial diseases and discovery of effective cures.

The mitophagy receptors BNIP3 and NIX mediate tight attachment and expansion of the isolation membrane to mitochondria

BNIP3 and NIX are the main receptors for mitophagy, but their mechanisms of action remain elusive. Here, we used correlative light EM (CLEM) and electron tomography to reveal the tight attachment of isolation membranes (IMs) to mitochondrial protrusions, often connected with ER via thin tubular and/or linear structures.

TANGO2 binds crystallin alpha B and its loss causes desminopathy

Mutations in the TANGO2 gene cause an autosomal recessive disorder characterised by developmental delay, stress-induced episodic rhabdomyolysis, and cardiac arrhythmias along with severe metabolic crises. Although TANGO2 mutations result in a well characterised disease pathology, the function of TANGO2 is still unknown. 

Mitochondrial damage in muscle specific PolG mutant mice activates the integrated stress response and disrupts the mitochondrial folate cycle

During mitochondrial damage, information is relayed between the mitochondria and nucleus to coordinate precise responses to preserve cellular health. One such pathway is the mitochondrial integrated stress response (mtISR), which is known to be activated by mitochondrial DNA (mtDNA) damage. However, the causal molecular signals responsible for activation of the mtISR remain mostly unknown.