The NTHL1 and NEIL1-3 DNA glycosylases are major enzymes in the removal of oxidative DNA base lesions, via the base excision repair (BER) pathway. It is expected that lack of these DNA glycosylases activities would render cells vulnerable to oxidative stress, promoting cell death. Intriguingly, we found that single, double, triple, and quadruple DNA glycosylase knockout HAP1 cells are, however, more resistant to oxidative stress caused by genotoxic agents than wild type cells. Furthermore, glutathione depletion in NEIL deficient cells further enhances resistance to cell death induced via apoptosis and ferroptosis. Finally, we observed higher basal level of glutathione and differential expression of NRF2-regulated genes associated with glutathione homeostasis in the NEIL triple KO cells. We propose that lack of NEIL DNA glycosylases causes aberrant transcription and subsequent errors in protein synthesis. This leads to increased endoplasmic reticulum stress and proteotoxic stress. To counteract the elevated intracellular stress, an adaptive response mediated by increased glutathione basal levels, rises in these cells. This study reveals an unforeseen role of NEIL glycosylases in regulation of resistance to oxidative stress, suggesting that modulation of NEIL glycosylase activities is a potential approach to improve the efficacy of e.g. anti-inflammatory therapies.

Background: CLN3 Batten disease is a severe pediatric neurodegenerative disorder caused by mutations in the CLN3 gene, most commonly a 1 kb deletion encompassing exons 7 and 8. CLN3 deficiency is associated with lysosomal dysfunction, impaired cellular clearance and disrupted metabolism. While neurons are particularly vulnerable in CLN3 Batten disease and have been the primary focus of research, glial cells are increasingly recognized as active contributors to disease pathology. Among them, astrocytes—the most abundant glial cell type in the brain—play critical roles in maintaining neuronal health and homeostasis. However, astrocytes remain understudied in CLN3 patient-derived models. Methods: We present the first iPSC-derived astrocyte model from a skin biopsy of a CLN3 patient carrying the common 1 kb deletion. Cellular and molecular features of iPSC and astrocytes derived from both healthy controls and the CLN3 patient were characterized via qPCR, immunocytochemistry and targeted mass spectrometry. In addition, comprehensive omics-based profiling, through transcriptomic and label-free quantitative proteomics, was performed to uncover novel molecular mechanisms and generate hypotheses that can guide future mechanistic and functional studies. Results: Transcriptomic and proteomic analyses during astrocyte differentiation revealed an upregulation of mitochondrial respiratory chain complexes I and IV—contrasting with the downregulation typically observed in CLN3-deficient neurons. We also identified a metabolic shift favoring the elongation of very-long-chain saturated fatty acids, accompanied by reduced lipid synthesis and enhanced fatty acid oxidation. These metabolic alterations were paralleled by an upregulation of proteins involved in oxidative stress responses, likely reflecting a compensatory adaptation to mitochondrial and lipid metabolic dysregulation. Furthermore, we observed significant changes in chromatin organization during astrocyte differentiation in CLN3 cells, suggesting epigenetic remodeling as a contributing factor to disease pathology. Conclusion: Our findings prompt the hypothesis that mitochondrial dysfunction may precede lysosomal defects in CLN3-deficient astrocytes. Restoring mitochondrial health could improve brain metabolism, inflammation control, neurotransmitter regulation, and neuronal survival, highlighting mitochondria as promising therapeutic targets in CLN3 Batten disease.