Investigating the impact and dynamic of mitochondrial common deletion in somatic cells

Project Summary: The most common mitochondrial DNA (mtDNA) abnormality is a deletion of 4977 base pairs called the common deletion (CD), associated with mitochondrial pathologies and widespread in aging. The CD primarily manifests in the brain and muscles when deleted molecules exceed 60% of total copies, known as heteroplasmy. However, the mechanisms that cause harmful deletions and why neuronal and muscle cells are particularly vulnerable to CD remain unclear. Major obstacles to studying the CD is the lack of tools to manipulate mtDNA and the inability to generate the CD in a controlled manner. Here, we developed a series of methodologies to overcome these barriers. Specifically, we generated an inducible quasi-dimeric TALEN that generates the CD in isogenic settings and at defined heteroplasmy states. With this tool, we will establish low, medium, and high levels of CD heteroplasmy in embryonic stem cells that we will then differentiate into muscle, neuronal, and fibroblast cells and elucidate the consequence of this harmful deletion in a cell-type-specific manner and its impact on cellular aging. Furthermore, we will explore the cell-type-specific distribution of CD, Identifying the pathways that sustain mutant mtDNA propagation in post-mitotic cells while promoting its elimination in dividing cells. Combining novel genetic tools with extensive experience in genome stability will resolve the long-standing mystery of preferential mutant mtDNA propagation in post-mitotic cells and have significant implications for numerous mitochondrial pathologies and aging.