Mitochondrial Genetics: Mitochondrial genome engineering to unravel the genetic links between mitochondrial gene regulation and human disease for future mechanism-based therapies

In eukaryotic organisms almost all genetic information is encoded in DNA present in the nucleus of the cell, but a small DNA molecule inhabits mitochondria, cellular structures that provide energy from food for the cells to use. Mitochondrial DNA contains genes that are vital for the physiological functioning of the cell, and genetic defects causing dysfunction of mitochondrial DNA can lead to human diseases. We still do not know how mitochondrial genes work exactly. One of the ways to investigate the role of a gene, or to discover its biological function, it to change or disrupt DNA, and then to look for the effect on cultured cells, or on the whole organism. These methods of genetic modification are often powerful ways of studying disease genes encoded in the nucleus, but they are challenging to be applied to mammalian mitochondrial DNA. Also, many genes regulating mitochondrial function are still unknown. Therefore, our research goals are to identify new genes regulating mitochondria, define how these mitochondrial genes operate and to provide the technology to allow mammalian mitochondrial DNA to be modified genetically. It could be an invaluable way of understanding mitochondrial diseases and for advancing the quest for therapies.

Mitochondrial diseases caused by mutations in mitochondrial DNA (mtDNA) or mutations in the nuclear genome (nDNA) impair energy metabolism and other aspects of cellular homeostasis. More than half of mitochondrial diseases stem from defects of mtDNA maintenance or expression. Our incomplete understanding of the underlying biology and scarcity of animal models of mtDNA disease hinders the development of curative treatments for these disorders.
The aims of the Mitochondrial Genetics programme are to engineer the mammalian mitochondrial genome to develop unique in vitro and in vivo models of mtDNA dysfunction and to exploit these models to interrogate mitochondrial genome regulation and to improve pre-clinical evaluation of treatments.
These future aims build upon considerable successes of the past quinquennium and leverage the emerging technical developments in direct DNA base editing. One way of achieving these objectives will be to generate an in vivo mouse model of single large-scale mtDNA deletions (SLSMDs) and use it, together with other existing mouse models, to refine pre-clinical gene therapy approaches aiming at elimination of heteroplasmic mutant mtDNA by programmable nucleases, and to investigate mtDNA regulation. In parallel, we will employ emerging DNA base-editing technology to install de novo mtDNA point mutations in vivo, to create a base-editor library for systematic ablation of all mtDNA-encoded protein and tRNA-coding genes in mice, and to generate mouse models mimicking the most common pathogenic mtDNA mutations (e.g. m.3243A>G). We will also continue our work on the mechanisms of mitochondrial gene expression; albeit with increasing involvement of mouse genetics and mtDNA-editing methods, focussing on knowledge gaps in quality control and decoding during mitochondrial translation and mitoribosome assembly.