Mutual regulation between RE1 Silencing Transcription Factor (REST) and Mitochondria in Neurodegenerative Disease

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Alzheimers disease (AD) is the most common form of dementia among the elderly with over 40 million individuals affected worldwide. AD is considered to be caused by neurotoxic protein aggregates of beta-amyloid (Ab) and tau that accumulate in the aging brain. However, this view is challenged by clinical observations and by the repetitive failure of AD clinical trials testing drugs that target these neurotoxic proteins. Recent evidence suggests that mitochondrial dysfunction precedes the formation of Ab plaques and neurofibrillary tau tangles, and that Ab and tau are not the primary cause of AD but rather promote neurodegeneration by exacerbating oxidative damage. The main risk factor for the development of AD is aging, and a common feature of the aging brain is reduced neuronal metabolic activity, increased oxidative stress and accumulating oxidative damage. It is hypothesized that such perturbed neuronal metabolism triggers a viscous cycle of further mitochondrial dysfunction and oxidative stress, which eventually results in neurodegeneration and AD. A recent discovery demonstrated that the RE1 silencing transcription factor (REST) is reactivated in the healthy ageing brain and controls a broad network of genes that protect from cell death, inflammation and AD pathology. However, the exact mechanism how neuronal REST levels are regulated during ageing remained elusive. This proposal is based on preliminary evidence indicating that REST controls cellular energy levels by restricting mitochondrial function. Interestingly, increased mitochondrial stress leads to the complete deletion of neuronal REST. These findings suggest that REST is part of a novel feedback mechanism that couples initial mitochondrial bioenergetic perturbations with a transcriptional collapse by deleting REST protein. This regulatory mechanism might distinguish healthy brain ageing from neurodegeneration and cognitive decline and should be further elucidated. Thus, the aim is to first establish REST knock out induced pluripotent stem cell (iPSC) lines using the CRISPR/Cas9-system. Subsequently they will be differentiated into neurons to assess mitochondrial function in REST knock out conditions. Secondly, I will assess the involvement of autophagy on REST expression and degradation. Lastly, endogenous REST will be tagged with a fluorescent protein in iPSC lines derived from AD patients and age matched controls, by CRISPR/Cas9. These lines will be used to firstly characterize REST expression in an in vitro model of AD. Finally, they will be used to clarify the implication of mitochondrial stress and autophagy on REST protein level.