Onji, M. | Search bioRxiv

bioRxiv2024

Reconstructing bat antiviral immunity using epithelial organoids

Bats are remarkably resilient to viruses with pandemic potential. To resolve largely unknown molecular mechanisms governing their exceptional antiviral immunity, we established an organoid platform to model the entire respiratory airway and intestinal epithelium of the important viral reservoir species Rousettus aegyptiacus (Egyptian fruit bat). These bat organoids exhibit an unexpected diversity of cell types and support replication of highly pathogenic zoonotic viruses including Marburg virus (MARV) and MERS-Coronavirus. Following virus infection, bat organoids unleash a strong interferon response, uniquely regulated through virus-dependent and virus-independent mechanisms. By contrast, MARV infected human organoids fail to induce an antiviral gene response and express pro-inflammatory cytokines after interferon stimulation, revealing important molecular differences between bats and humans with implications for lethal Marburg virus infections in primates. These data provide the most comprehensive organoid platform in bats to decode species-specific differences and uncover fundamental principles of bat disease resilience to emerging viruses with pandemic potential.

immunology↗

bioRxiv2023

Crucial neuroprotective roles of the metabolite BH4 in dopaminergic neurons

Dopa-responsive dystonia (DRD) and Parkinsons disease (PD) are movement disorders caused by the dysfunction of nigrostriatal dopaminergic neurons. Identifying druggable pathways and biomarkers for guiding therapies is crucial due to the debilitating nature of these disorders. Recent genetic studies have identified variants of GTP cyclohydrolase-1 (GCH1), the rate-limiting enzyme in tetrahydrobiopterin (BH4) synthesis, as causative for these movement disorders. Here, we show that genetic and pharmacological inhibition of BH4 synthesis in mice and human midbrain-like organoids accurately recapitulates motor, behavioral and biochemical characteristics of these human diseases, with severity of the phenotype correlating with extent of BH4 deficiency. We also show that BH4 deficiency increases sensitivities to several PD-related stressors in mice and PD human cells, resulting in worse behavioral and physiological outcomes. Conversely, genetic and pharmacological augmentation of BH4 protects mice from genetically- and chemically induced PD-related stressors. Importantly, increasing BH4 levels also protects primary cells from PD-affected individuals and human midbrain-like organoids (hMLOs) from these stressors. Mechanistically, BH4 not only serves as an essential cofactor for dopamine synthesis, but also independently regulates tyrosine hydroxylase levels, protects against ferroptosis, scavenges mitochondrial ROS, maintains neuronal excitability and promotes mitochondrial ATP production, thereby enhancing mitochondrial fitness and cellular respiration in multiple preclinical PD animal models, human dopaminergic midbrain-like organoids and primary cells from PD-affected individuals. Our findings pinpoint the BH4 pathway as a key metabolic program at the intersection of multiple protective mechanisms for the health and function of midbrain dopaminergic neurons, identifying it as a potential therapeutic target for PD.

neuroscience↗