Exploring the role of endogenous DNA damage in neurodegeneration

Abstract

DNA repair pathways are critical signal transduction pathways that maintain genomic stability and ensure DNA remains stable through the life of a cell. These pathways mitigate stresses that arise both endogenously and exogenously. Endogenous DNA damage arises from a variety of sources, including metabolism, chromatin remodelling, transcription, and replication stress. Defective DNA repair machinery leads to various human diseases. Underlying these diseases is – at a basic level – the inability to counteract specific types of genotoxic stressors. The human diseases that emerge from mutations in DNA repair genes have specific phenotypes and pathologies, often including neurological, and indeed in some cases neurodegenerative features. While the links between cancer and DNA repair have been studied at great depths, the links between the central nervous system and DNA repair remain an underexplored area of research. In order to elucidate the specific relevance of DNA repair at the genetic and functional levels, the study of specific diseases and phenomena offer good models to increase our understanding. To that end, I present the beginnings of three such explorations. First, I interrogated a genetic modifier of Huntington’s disease known as FAM193A and demonstrated its specific synthetic lethal relationship with nucleotide analogue drugs. In addition, I performed a whole genome CRISPR/Cas9 screen. Subject to validation, the screen demonstrated that inhibition of proteins in key pathways, such as chromatin regulation and transcription, rescued the synthetic lethality between Fam193a and 5-fluorouracil. Second, I assessed familial Parkinson’s disease gene, PARK7, based on reports suggesting it has a role in oxidative and carbonyl stress mitigation. I was not able to recapitulate previous findings and did not observe any particular DNA repair signature. In turn, I sought to study the nature of a potentially two-tier defence system consisting of GLO1/2 and PARK7 by creating a model to study glycation-induced DNA damage by knocking out GLO1, the primary quencher of reactive carbonyls. This serves to, theoretically, overload the system with reactive species by exceeding the cellular capacity to maintain genomic integrity. Third, following previous efforts by colleagues to understand the genetic determinants of micronucleus formation – another DNA damage-linked phenomenon associated with neurological phenotypes – I began validating and exploring some of the mechanistic underpinnings of DSCC1-induced genomic instability caused by defective sister chromatid cohesion. In addition, I demonstrate that SIRT1 inhibition can rescue DSCC1 deficient cells and lay out my hypothesis as to how this may occur. I also offer a roadmap of experiments that could serve to illuminate the mechanism.