Prevention of neuronal degeneration in human mitochondria-associated diseases (HMAD): C. elegans as a model organism for high-content screenings

Mitochondria play a pivotal role in controlling cellular homeostasis. The mitochondrial respiratory chain is severely compromised in different human mitochondrial-associated diseases (HMAD), resulting in oxidative stress and reduced ATP production, ultimately leading to degeneration of affected tissues. Similarly, in the nematode Caenorhabditis elegans, severe mitochondrial disruption leads to deleterious effects such as developmental arrest or lethality. On the other hand partial mitochondrial disruption in different species, including C. elegans, prolongs lifespan. Different and distinct reproducible phenotypes are therefore associated in the nematode C. elegans with different levels of mitochondrial stress and were used in the first part of my study as a readout for an RNAinterference screening aimed at developing different HMAD models, which mimic different phases of the disease progression. I then systematically characterized some of the new models with a special emphasis on neuronal deficits evaluation. Investigating the molecular mechanisms underlying the transition in animal phenotypes (from mild to severe mitochondrial stress), and in particular the characterization of the adaptive beneficial pathways extending lifespan in response to mild mitochondrial stress, may lead to the identification of genes likely relevant for the prevention or delay of neurodegenerative or age-related diseases associated with progressive mitochondrial deterioration. With this aim in mind, in the second part of my thesis I assessed neuronal structure and functions during animal aging and investigated the involvement of specific neuronal genes (chemosensory-related genes and globins) in lifespan specification, upon mild mitochondrial stress. I demonstrated that a moderate mitochondrial alteration leads to increase animal’s lifespan through neuronal hormesis. Finally, taking advantage of an automated microscopy platform (the Cellomics ArrayScan VTI HCS Reader) coupled with the typical phenotypic readouts observed in C. elegans in response to different level of mitochondrial stress, I optimized and validated the conditions to carry out an in vivo, high-content screening (HCS) aimed at identifying interventions inducing beneficial mitochondrial stress responses. This platform will offer the double opportunity to screen for potential HMADs therapeutics as well as for general anti-aging drug