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Insights from multi-omic modelling of neurodegeneration in Xeroderma Pigmentosum using an induced pluripotent stem cell system

ABSTRACT: Xeroderma pigmentosum (XP) is caused by defective nucleotide excision-repair of DNA damage. This results in hypersensitivity to ultraviolet light and increased skin cancer risk, as sunlight-induced photoproducts remain unrepaired. However, many XP patients also display early-onset neurodegeneration, which leads to premature death. The mechanism of neurodegeneration is unknown. Here, we investigate XP neurodegeneration using pluripotent stem cells derived from XP patients and healthy relatives, performing functional multi-omics on samples during neuronal differentiation. We show substantially increased levels of 5',8-cyclopurine and 8-oxopurine in XP neuronal DNA secondary to marked oxidative stress. Furthermore, we find that the endoplasmic reticulum stress response is upregulated and reversal of the mutant genotype is associated with phenotypic rescue. Critically, XP neurons exhibit inappropriate downregulation of the protein clearance ubiquitin-proteasome system (UPS). Chemical enhancement of UPS activity in XP neuronal models improves phenotypes, albeit inadequately. Although more work is required, this study presents insights with intervention potential.

INSTRUMENT(S): Orbitrap Fusion Lumos

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Graeme Benstead-Hume

LAB HEAD: Jyoti Choudhary

PROVIDER: PXD047571 | Pride | 2024-04-18

REPOSITORIES: Pride

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Project description:Cerebrovascular dysfunction is a hallmark feature of Alzheimer's disease (AD). One of the greatest risk factor for AD is the apolipoprotein E4 (E4) allele. APOE4 genotype has been shown to negatively impact on perivascular amyloid clearance, however, its direct influence along with the other APOE variants (APOE2 and APOE3) on the molecular integrity of the cerebrovasculature has not been largely explored. To address this, we employed a 10-plex tandem isobaric mass tag approach in combination with an ultra-high pressure liquid chromatography MS/MS (Q-Exactive) method, to interrogate unbiased proteomic changes in cerebrovessels from AD and healthy control brains on different APOE genotype backgrounds. We first interrogated changes between healthy control homozygote E2/E2, E3/E3 and E4/E4 cases to identify underlying genotype specific effects on cerebrovessels. EIF2 signaling, regulation of eIF4 and 70S6K signaling and mTOR signaling were the top significantly altered pathways in E4/E4 compared to E3/E3 cases. EIF2, nitric oxide and sirtuin signaling pathways were the top significantly altered pathways in E4/E4 compared to E2/E2 cases. We used a Two-way ANOVA analysis to identify AD-dependent changes and their interactions with APOE genotype. The highest number of significantly regulated proteins from this interaction was observed in E3/E4 (192) and E4/E4 (189) cases. As above, EIF2, mTOR signaling and eIF4 and 70S6K signaling were the top three significantly altered pathways in E4 allele carriers (i.e. E3/E4 and E4/E4 genotypes). Of all the cerebrovascular cell specific markers identified in our proteomic analyses, endothelial cell, astrocyte, and smooth muscle cell specific protein markers were significantly altered in E4/E4 cases, while endothelial cells and astrocyte specific protein markers were altered in E3/E4 cases. These proteomic changes provide novel insights to explain the longstanding link between APOE4 and cerebrovascular dysfunction. The early and converging APOE4 dependent changes we identified could provide novel targets in the cerebrovasculature for developing disease modifying strategies to mitigate the effects of APOE4 genotype on increasing the risk for, and the path towards AD pathogenesis.

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Insights from multi-omic modelling of neurodegeneration in Xeroderma Pigmentosum using an induced pluripotent stem cell system

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