Genetic Manipulation to Stress Granule Components Modifies Neurodegeneration in Drosophila Models of Amyotrophic Lateral SclerosisdissertationsSarkisian, EmilycreatorWharton, KristiAdvisorLarschan, EricaReaderRand, DavidReaderBrown University. Biology and Medicine: Biotechnologysponsor2025, 71 p.born digitalThesis (Sc. M.)--Brown University, 2025thesesStress granules (SG) are membraneless, ribonucleoprotein structures that assemble as a protective response to stress in the cell. In the presence of chronic stress, SGs fail to dissolve, leading to persistent aggregation of proteins and stalled mRNA translation. SG dysfunction is a hallmark of many neurodegenerative diseases, including amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD), yet it is unclear whether SG dysfunction is causative to these disorders or is in response to neurodegeneration. Mutations to the genes C9orf72 and TARDBP are seen in both sporadic and familial forms of ALS/FTD. We developed an adult-onset Drosophila model of C9orf72-(G4C2)49 ALS, wherein adult flies exhibit a shortened lifespan and exacerbated decrease in climbing velocity with age. Using this and a motor neuron-driven dTARDBP patient allele (TBPH[N493D]), we tested if knocking down four SG-associated genes of interest using RNAi had any effect on neurodegeneration phenotypes in these two models. These genes (Heterogeneous nuclear ribonucleoprotein at 27C (Hrb27C), Tudor staphylococcal nuclease (Tudor-SN), maleless (mle), and ovarian tumor (otu)) were selected from a screen that identified ~150 novel human SG components (Markmiller et al., 2018). As shown previously, RNAi knockdown of each gene reduces a rough eye phenotype indicative of neurodegeneration when mutant human proteins are expressed in Drosophila photoreceptors (GMR>hTDP-43[M337V] and hFUS[R521C]). To better understand the extent to which these four SG genes alleviate neurotoxicity, we assessed ALS-associated defects in viability (eclosion), motor function (climbing), and survival (lifespan) and how it may be modified by knockdown of each gene. The ability to suppress neurotoxicity associated with C9orf72-(G4C2)49 ALS and TBPH[N493D] ALS models varied with each gene knockdown. We also assessed the pathological hallmark of TDP-43 ALS which includes toxic protein aggregation in the cytoplasm of the cell. We observe that knockdown of SG-associated genes can re-localize the protein to the nucleus. Our analysis highlights the dynamic role of SG-associated genes in ALS pathology.Drosophila melanogasterAmyotrophic lateral sclerosisNeurodegenerationStress GranulesEnglishRPB20250707