INHIBITING THE NUCLEAR RECEPTOR ESRRA RESCUES CORE PATHOLOGIES IN CELLULAR AND ANIMAL MODELS OF BATTEN DISEASE

Batten disease (BD), a group of fatal neurodegenerative lysosomal storage disorders, is characterized by vision loss, cognitive decline, and seizures. Our lab recently identified the accumulation of the glycosphingolipid Gb3 as a key pathological hallmark in multiple BD subtypes (Soldati et al., 2021). However, the underlying molecular mechanism is unknown. This thesis aims to identify the genes controlling Gb3 accumulation, paving the way for new small-molecule therapies capable of penetrating the central nervous system. Thus, to find genes involved in Gb3 buildup, we performed a high-content imaging screen using a library of approximately 11,000 siRNAs (small interfering RNAs, which silence specific genes) in a human ARPE-19 CLN3 knockout (CLN3KO) cell model. The survey identified 84 candidate genes whose depletion reduced Gb3 levels. We focused on the top candidate hit, Estrogen-related receptor alpha (ESRRA/ESRRA), a nuclear receptor involved in mitochondrial biogenesis, lipid metabolism, and autophagy. Both genetic silencing and pharmacological inhibition of ESRRA with the inverse agonist XCT-790 significantly reduced Gb3 accumulation in both CLN3 and CLN7 disease models, suggesting that ESRRA may represent a novel therapeutic target for multiple BDs. Transcriptomic analysis revealed that pharmacological inhibition of ESRRA with XCT-790 triggers a beneficial metabolic reprogramming by further suppressing defective mitochondrial respiration, activating the PPARG pathway, and inducing the expression of FOX3a, a transcription factor involved in the transcriptional activation of autophagy. Indeed, ESRRA inhibition enhances cellular clearance by boosting autophagic flux by mechanism independent of the nuclear translocation of the master gene of lysosomal biogenesis and autophagy TFEB. To validate these findings in a living organism, we treated CLN7 knockout mice with XCT-790 via dietary supplementation of the compound. The treatment successfully reduced Gb3 and SCMAS accumulation in the brain's cortex and cerebellum, and ameliorated neuroinflammation and motor phenotype. Collectively, this research identifies ESRRA as a novel druggable target for Batten disease. Our findings demonstrate that ESRRA is a novel druggable target and its inhibitor XCT-790 ameliorate disease hallmarks in vitro and in vivo, offering significant therapeutic potential, and a new strategy to restore both lysosomal and mitochondrial function across multiple, distinct subtypes of BDs.