Saturday, September 7, 2024
9/7/2024
PROJECT SUMMARY / ABSTRACT Mitochondrial dysfunction (MD) plays a central role in the pathophysiology of many human diseases commonly referred as non-communicable diseases (NCDs). NCDs are non-infectious, non-transmissible disorders characterized by low-grade chronic inflammation, among which the most common are obesity, insulin resistance, diabetes, forms of cancer, cardiovascular diseases, and nonalcoholic fatty liver disease. NCDs affect an estimated 41 million people each year. Additionally, MD has also been implicated in aging and age-related diseases, including neurological disorders such as Alzheimer's disease and related dementias, which represent the sixth-leading cause of death in the United States, with cost for long-term and hospice care calculated to be around 200 billion dollars per year. One cause of MD is an increase in mitochondrial DNA (mtDNA) mutations resulting in impaired oxidative phosphorylation that leads to loss of bioenergetic homeostasis, increased cell apoptosis, and senescence. To address the role of mtDNA mutations on tissue/organ homeostasis, two independent groups developed a knock-in mouse expressing a proofreading-deficient version of the nucleus- encoded catalytic subunit of mtDNA polymerase-γ (PolgA). The mtDNA mutator mouse model demonstrates a cause-and-effect relationship between slowly increasing somatic mtDNA mutation levels and several phenotypes associated with aging that manifest much earlier in life, including reduced lifespan, weight loss, alopecia, anemia, kyphosis, osteoporosis, sarcopenia, and loss of subcutaneous fat. Although this mouse model has been key to understand the effect of mtDNA mutations driven MD on organismal health, the global MD results in overall tissue/organ dysfunction and makes it difficult to dissect how different tissues are affected and compensate for MD, since it has not possible to separate single organ dysfunction from other organs equally affected by MD. Moreover, due to the overall marked and severe progeroid phenotypes that affect the auditory, visual, and ambulatory systems in this model, it has not been possible to test how MD affects brain health and cognition. To overcome this limitation, we have generated a novel knock-in inducible mtDNA mutator mouse (RJA- PolgACDS/CDS) with both spatial and temporal regulation capabilities that will allow us to study the effect of mtDNA mutation-induced MD in single tissues at different time-points. The overall goal of this proposal is to validate this new mouse model and demonstrate its utility in studying the role of MD in a broad range of human diseases. We will test its temporal and spatial inducibility by crossing it with a whole-body expressing Cre mouse (Aim 1) as well as inducible (CreERT2) and muscle-specific (ACTA1-Cre) Cre-expressing mouse lines (Aim 2). The proposed work is highly responsive in addressing important knowledge gaps in understanding the role of MD on organ homeostasis, including its role on onset and progression of many human diseases. Successful completion of this work will provide a novel and unique animal model to investigate the relationship between MD and several diseases and will provide a novel platform to investigate therapeutic strategies to target these pathologies.
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