Biology subjects

Gunther, S.

Publications and source records attributed to Gunther, S..

6 recordsLinked to original sources

bioRxiv2024

flt1 inactivation promotes zebrafish cardiac regeneration by enhancing endothelial activity and limiting the fibrotic response

Summary statementflt1 inactivation promotes zebrafish cardiac regeneration by enhancing coronary revascularization and endocardial expansion, while limiting myofibroblast differentiation. VEGFA administration has been explored as a pro-angiogenic therapy for cardiovascular diseases including heart failure for several years, but with little success. Here we investigate a different approach to augment VEGFA bioavailability: by deleting the VEGFA decoy receptor VEGFR1/FLT1, one can achieve more physiological VEGFA concentrations. We find that following cryoinjury, zebrafish flt1 mutant hearts display enhanced coronary revascularization and endocardial expansion, increased cardiomyocyte dedifferentiation and proliferation, and decreased scarring. Suppressing Vegfa signaling in flt1 mutants abrogates these beneficial effects of flt1 deletion. Transcriptomic analyses of cryoinjured flt1 mutant hearts reveal enhanced endothelial MAPK/ERK signaling and downregulation of the transcription factor gene egr3. Using newly generated genetic tools, we observe egr3 upregulation in the regenerating endocardium, and find that Egr3 promotes myofibroblast differentiation. These data indicate that with enhanced Vegfa bioavailability, the endocardium limits myofibroblast differentiation via egr3 downregulation, thereby providing a more permissive microenvironment for cardiomyocyte replenishment after injury.

molecular biology↗

bioRxiv2024

The transmembrane glycoprotein Gpnmb is required for the immune and fibrotic responses during zebrafish heart regeneration

Myocardial infarction occurs when coronary supply of oxygen and nutrients to part of the heart is interrupted. In contrast to adult mammals, adult zebrafish have a unique ability to regenerate their heart after cardiac injury. Several processes are involved in this regenerative response including inflammation, coronary endothelial cell proliferation and revascularization, endocardial expansion, cardiomyocyte repopulation, and transient scar formation. To identify potential regulators of zebrafish cardiac regeneration, we profiled the transcriptome of regenerating coronary endothelial cells at 7 days post cryoinjury (dpci) and observed the significant upregulation of dozens of genes including gpnmb. Gpnmb (glycoprotein non-metastatic melanoma protein B) is a transmembrane glycoprotein implicated in inflammation resolution and tissue regeneration. Transcriptomic profiling data of cryoinjured zebrafish hearts reveal that gpnmb is mostly expressed by macrophages. To investigate gpnmb function during zebrafish cardiac regeneration, we generated a full locus deletion (FLD) allele. We find that after cardiac cryoinjury, animals lacking gpnmb exhibit neutrophil retention and decreased macrophage recruitment as well as reduced myofibroblast numbers. Moreover, loss of gpnmb impairs coronary endothelial cell regeneration and cardiomyocyte dedifferentiation. Transcriptomic analyses of cryoinjured gpnmb mutant hearts identified enhanced collagen gene expression and the activation of extracellular matrix (ECM) related pathways. Furthermore, gpnmb mutant hearts exhibit larger fibrotic scars revealing additional defects in cardiac regeneration. Altogether, these data indicate that gpnmb expressing macrophages modulate inflammation and ECM deposition after cardiac cryoinjury in zebrafish and further highlight the importance of this subset of immune cells to support a regenerative response.

molecular biology↗

bioRxiv2024

TNF Superfamily Member 14 Drives Post-Influenza Depletion of Alveolar Macrophages Enabling Secondary Pneumococcal Pneumonia

Secondary bacterial infection, often caused by Streptococcus pneumoniae (Spn), is one of the most frequent and severe complications of influenza A virus (IAV)-induced pneumonia. Phenotyping of the pulmonary innate immune landscape after IAV infection revealed a significant depletion of the tissue-resident alveolar macrophage (TR-AM) population at day 7, which was associated with increased susceptibility to Spn outgrowth. To elucidate the molecular mechanisms underlying TR-AM depletion, and to define putative targets for treatment, we combined single-cell transcriptomics and cell-specific PCR profiling in an unbiased manner, using in vivo models of IAV infection and IAV/Spn co-infection. The TNF superfamily 14 (TNFSF14) ligand-receptor axis was revealed as the driving force behind post-influenza TR-AM death during the early infection phase, enabling the transition to pneumococcal pneumonia, while intrapulmonary transfer of genetically modified TR-AMs and antibody-mediated neutralization of specific pathway components alleviated disease severity. With a mainly neutrophilic expression and a high abundance in the bronchoalveolar fluid (BALF) of patients with severe virus-induced ARDS, TNFSF14 emerged as a novel determinant of virus-driven lung injury. Targeting the TNFSF14-mediated intercellular communication network in the virus-infected lung can, therefore, improve host defense, minimizing the risk of subsequent bacterial pneumonia, and ameliorating disease outcome.

molecular biology↗

bioRxiv2023

Structural elucidation and antiviral activity of cathepsin L inhibitors with carbonyl and epoxide warheads

Emerging RNA viruses including SARS-CoV-2 continue to be a major threat around the globe. The cell entry of SARS-CoV-2 particles via the endosomal pathway involves the cysteine protease cathepsin L (CatL) among other proteases. CatL is rendered as a promising drug target in the context of different viral and lysosome-related diseases. Hence, drug discovery and structure-based optimization of inhibitors is of high pharmaceutical interest. We herein verified and compared the anti-SARS-CoV-2 activity of a set of carbonyl and succinyl-epoxide-based inhibitors, which have previously been identified as cathepsin inhibitors. Calpain inhibitor XII (CI-XII), MG-101 and CatL inhibitor IV (CLI-IV) possess antiviral activity in the very low nanomolar IC50 range in Vero E6 cells. Experimental structural data on how these and related compounds bind to CatL are however notably lacking, despite their therapeutic potential. Consequently, we present and compare crystal structures of CatL in complex with 14 compounds, namely BOCA (N-BOC-2-aminoacetaldehyde), CLI-IV, CI-III, CI-VI, CI-XII, the main protease -ketoamide inhibitor 13b, MG-101, MG-132 as well as E-64d (aloxistatin), E-64, CLIK148, CAA0225, TC-I (CID 16725315) and TPCK at resolutions better than 2 [A]. Overall, the presented data comprise a broad and solid basis for structure-guided understanding and optimization of CatL inhibitors towards protease drug development.

biochemistry↗

bioRxiv2021

Predicting the evolution of Lassa Virus endemic area and population at risk over the next decades

Lassa fever is listed among the diseases that pose the greatest risks to public health by the World Health Organization. This severe viral hemorrhagic fever is caused by Lassa virus, a zoonotic pathogen that repeatedly spills over to humans from its rodent reservoirs. It is currently not known how climate change, transformations in land use, and human population growth could affect the endemic area of this virus, currently limited to parts of West Africa. By exploring the environmental data associated with virus occurrence, we show how temperature, precipitation and the presence of pastures determine ecological suitability for virus circulation. We project that regions in Central and East Africa will likely become suitable for Lassa virus over the next decades and estimate that the total population living in areas suitable for Lassa virus may grow from about 100 million to 700 million by 2070. By analysing geotagged viral genomes, we find that in the event of Lassa virus being introduced into a new suitable region, its spread might remain spatially limited over the first decades. Our results highlight how the endemic area of Lassa virus may expand well beyond West Africa in the next decades due to human impact on the environment, putting hundreds of million more people at risk of infection.

microbiology↗

bioRxiv2019

Rift Valley fever virus minigenome system for investigating the role of L protein residues in viral transcription and replication

Replicon systems are important molecular tools for investigating the function of virus proteins and regulatory elements involved in viral RNA synthesis. We developed an ambisense minigenome system for Rift Valley fever virus (RVFV) to dissect the effects of L gene mutations on viral transcription versus replication. The S RNA segment with regulatory elements for ambisense gene expression served as backbone for the minigenome. Expression of the luciferase reporter gene allowed the overall activity of the RVFV replication complex to be assessed, while northern blot analysis enabled differentiation between synthesis of viral mRNA and replication intermediates. The functionality of the system was demonstrated by probing residues predictably involved in the active site of the cap-snatching endonuclease in the N-terminus of the L protein. Corresponding mutations led to a selective defect in the viral mRNA synthesis as described for other viruses of the Bunyavirales order. The analysis of further L gene mutants revealed an essential and specific role of a C-terminal region in the RVFV L protein in viral transcription. In summary, the established minigenome system is suitable for functional testing of the relevance of residues for viral transcription and replication. It may be used to validate hypotheses arising from structural or biochemical investigations of the RVFV replication complex.

molecular biology↗