Bridging the gap in mitochondrial disorder diagnosis and treatment by using human embryos and pluripotent stem cells

Mitochondrial DNA (mtDNA) diseases primarily originate from defects in the mtDNA, typically manifesting in a heteroplasmic manner with cells containing both wild-type and mutated mtDNA copies. The mutation load in cells represents the proportion of mutant-to-wild type mtDNA. In the absence of therapeutic treatment, overcoming transmission of mtDNA disorders is a must. Preimplantation genetic diagnosis allows for selection of embryos with no or low detectable mutation load. As a first objective, we will verify the efficiency of next generation sequencing for determining mutation load, as well as measuring mtDNA copy number in cells and embryos from patients with a known mtDNA mutation. At present, the mechanisms regulating mutant mtDNA variant segregation and progression remain largely unknown. Hence, we aim to derive induced pluripotent stem cells (iPSCs) from individuals with a known mitochondrial disorder, providing a unique and extremely valuable model for studying the pathophysiology of these disorders in vitro. We will explore the segregation pattern of wild-type and mutated mtDNA in iPSCs during self-renewal and differentiation. More specifically, we aim to verify how the mutation load affects the functionality of these cells, with a particular focus on differentiation potential and respiratory rates. Finally, we will evaluate the efficacy and safety of currently proposed nuclear transfer techniques to overcome transmission of mitochondrial diseases in humans.