Biology subjects

Meier, K.

Publications and source records attributed to Meier, K..

12 recordsLinked to original sources

bioRxiv2026

Immunomodulatory RIG-I Agonist SLR14 Confers Protection Against a Range of Highly Pathogenic Negative Sense RNA viruses

Emerging and re-emerging zoonotic RNA viruses, including filoviruses, henipaviruses and Rift Valley Fever virus (RVFV), pose a significant threat to human health. Due to their epidemic potential and high pathogenicity, these viruses are categorized as WHO priority pathogens, yet we still lack effective medical countermeasures (MCMs) against most of these dangerous pathogens, supporting that host-directed antivirals will be advantageous for broadly acting MCMs. Here we assessed the antiviral efficacy of SLR14, an immunomodulatory stem-loop RNA that activates RIG-I, for its activity against a panel of highly pathogenic viruses. SLR14 treatment provided broad-spectrum protection, markedly reducing infection with Ebola virus (EBOV), Marburg virus, and Sudan virus in human primary monocyte-derived macrophages, and Nipah virus replication in iPSC-derived endothelial cells, whether administered prophylactically or therapeutically. In vivo, a single dose of SLR14 protected mice against lethal RVFV infection when administered prophylactically, and, notably, retained significant efficacy when administered up to two days post-infection. Therapeutic SLR14 administration also improved survival rates of EBOV-infected mice. Although EBOV infection and SLR14 treatment activated overlapping innate immune pathways in human macrophages, viral infection induced a nonprotective response, whereas SLR14 elicited a well-regulated, markedly stronger and protective interferon-stimulated and inflammatory gene signature while avoiding prolonged IFN gene upregulation. Our data identify SLR14 as a potent host-directed therapeutic with broad antiviral efficacy against some of the most lethal viral pathogens.

microbiology↗

bioRxiv2026

Ebola virus mRNAs contain RNA structures that are critical for viral infection and targetable by antisense oligonucleotides

Filoviruses, such as Ebola virus (EBOV), are highly pathogenic non-segmented negative-sense RNA viruses (nsNSVs) with limited therapeutic options. Filovirus RNA structures remain largely untapped due to the enhanced biosafety requirements for handling infectious virus. Here, we present the first in-cell secondary structure maps of four EBOV mRNAs (VP35, VP40, VP30, and VP24) using two orthogonal chemical probing approaches: SHAPE-MaP and fbDMS-MaP. We find that EBOV mRNA coding sequences (CDS) are highly structured, much like +ssRNA viruses, whereas untranslated regions (UTRs) are significantly less structured. This suggests that high CDS structure contents are general features of viral translation templates, and that nsNSVs have evolved separate regulatory function at the RNA structure level that extends beyond using distinct mRNAs and genomes. These structure maps are consistent with formation of mRNA 5' hairpin structures during infection and reveal numerous additional RNA structures within the CDS, 3' UTRs, and at CDS-UTR junctions. To assess functionality, we disrupted these structures with locked nucleic acid (LNA) antisense oligonucleotides. Disrupting the TSS hairpins in VP35, VP30, and VP24 decreased infection by >60%, indicating these mRNA structures are critical for infection. LNA targeting of the newly identified structures reduced EBOV infection by 31% to 88%, thereby linking RNA structural integrity to viral function. Synonymous mutation rates and covariation analysis provided evolutionary support across mammalian filoviruses for the functional RNA elements observed. Collectively, these results demonstrate EBOV mRNAs contain numerous conserved RNA motifs contributing to viral infection, and that these elements represent promising targets for development of pan-filoviral therapeutics.

microbiology↗

bioRxiv2026

Tunable Laminar Perfusion Coordinates Endothelial and Perivascular Remodeling in Angiogenic Vasculature-on-Chip

Perfusable vascular microphysiological systems are increasingly used to model angiogenesis, tissue crosstalk, and disease. However, many platforms still rely on oscillatory, discontinuous, or poorly controlled perfusion regimes, limiting the study of sustained flow-dependent vascular remodeling. Here, we establish a tunable, unidirectional laminar flow workflow for long-term perfusion of angiogenic vasculature-on-chip cultures and use it to investigate endothelial, perivascular, and immune cell responses to sustained flow. Using an AIM Biotech microfluidic platform containing 14-day-old human umbilical vein endothelial cell-derived angiogenic sprouts and pericytes, continuous perfusion enabled intraluminal transport of 1 m tracer beads through vessels, demonstrating stable flow across the vascular bed. Sustained laminar flow induced endothelial remodeling at both the mother vessel and sprout levels, with cellular alignment evident in both compartments. Quantitative analysis of the mother vessel further revealed Golgi polarization against the direction of flow. Sustained perfusion also increased pericyte recruitment to angiogenic sprouts and reduced endothelial proliferation within the mother vessel, consistent with flow-driven vascular maturation and quiescence. Live-cell imaging further captured directional endothelial migration against the flow, lumen remodeling, and dynamic pericyte behavior under continuous perfusion. In immune-cell assays performed under continuous-flow conditions, interactions with untreated endothelium were limited, whereas inflammatory activation increased immune-cell adhesion and crawling. These observations suggest that sustained flow supports a quiescent endothelial phenotype and demonstrate the suitability of the platform for studying inflammatory activation and immune-vascular communication under controlled hemodynamic conditions. Beyond its biological relevance, the workflow provides practical advantages for live-cell imaging, low medium consumption, and downstream perturbation studies. Moreover, the modular design of the platform makes it well suited for vascular-organ crosstalk applications. Collectively, these results establish laminar flow angiogenic vasculature-on-chip as an experimentally tractable model for studying vascular mechanobiology, vascular maturation, and dynamic cell interactions under defined hemodynamic conditions.

bioengineering↗

bioRxiv2026

Endothelial YAP/TAZ rewiring under cardiometabolic stress drives sex-divergent vascular remodeling in heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is widely linked to endothelial dysfunction, yet the molecular pathways translating cardiometabolic stress into microvascular remodeling remain poorly defined. Here, we identify endothelial YAP/TAZ signaling as a mechanistic regulator of sex-divergent vascular responses in HFpEF. Plasma proteomics from the UK Biobank revealed elevated circulating YAP1 levels associated with heart failure and increased mortality, particularly in male patients, where YAP1 coincided with increased levels of the endothelial activation marker ESM1. In a hypertensive cardiorenal mouse model, endothelial YAP/TAZ deletion preserved cardiac function, whereas endothelial TAZ gain-of-function aggravated disease. Under cardiometabolic stress (TNF and high glucose), endothelial cells exhibited sex-specific rewiring of YAP/TAZ-dependent transcriptional programs. Male endothelial cells showed increased extracellular YAP1 release, angiogenic instability with impaired extracellular matrix remodeling, whereas female cells adopted an immune-primed, stress-adaptive phenotype. Mechanistically, cardiometabolic stress uncoupled canonical YAP-TEAD transcription and engaged alternative cofactors, including VGLL3 and VGLL4, thereby reshaping the endothelial secretome and propagating sex-divergent microvascular remodeling. These findings identify endothelial YAP/TAZ rewiring as a molecular switch that converts cardiometabolic stress into sex-divergent microvascular remodeling in HFpEF and connect this process to circulating YAP1 and ESM1 in patients.

cell biology↗

bioRxiv2024

Glioblastoma cells imitate neuronal excitability in humans

BackgroundGlioblastomas are renowned for their pronounced intratumoral heterogeneity, characterized by a diverse array of plastic cell types. However, the physiological and transcriptomic features of the cells residing in the invasive leading edge (LE), including both neurons and glioblastoma cells (GBCs), remain unclear, challenging our comprehension of the glioblastoma pathophysiology. MethodsTo elucidate molecular and morphophysiological features of LE cells, we established an experimental workflow enabling the investigation of GBCs and neurons within cancer-infiltrated organotypic tissue specimens from the same patients. With this approach, we characterized the electrophysiological properties of cells in the neocortical tumor LE (LE cells). We further performed single-cell Patch-seq experiments, enabling transcriptomic analysis of electrophysiologically recorded LE cells. ResultsUpon depolarization, 58% of LE cells exhibited aberrant action potentials (aAPs). Electrophysiological assessment showed that a subset of GBCs generated aAPs, with no significant differences in aAP properties compared to LE neurons. Transcriptomic analysis of 144 LE cells revealed four transcriptomic clusters, including two GBC populations and two neuronal populations. LE GBCs exhibited diverse cellular states, including mesenchymal-like, astrocyte-like, neural progenitor-like, and oligodendrocyte-precursor cell-like phenotypes. Notably, LE GBCs exhibiting aAPs displayed reduced mitotic pathway activity and developmental regulatory ion channel CaV1.2. Cell-cell interaction analysis illustrates a higher signaling interaction between aAP LE cells compared to no-aAP LE cells. ConclusionIn summary, we find comparable electrical properties between neurons and a subset of GBCs in the leading edge, suggesting an active electrophysiological role of GBCs in the tumors pathophysiology. Key PointsO_LIHuman organotypic slice cultures enable long-term functional investigation of glioblastoma cells. C_LIO_LIGBCs and neurons in the LE exhibit similar aAPs. C_LIO_LILE GBCs display heterogeneous cellular states, with reduced proliferation signaling in aAP GBCs. C_LI Importance of studyThis study sheds light on the diverse pathophysiological and molecular features of cells in the neocortical infiltration zone of glioblastoma. By utilizing in vitro organotypic human brain slice cultures, a reliable platform for longitudinal observation, we unveiled the dichotomy of the electrical properties of LE cells. More than half of LE cells display aAP, contradicting findings from cultured tumor cells and animal models. Patch-seq analysis confirmed that both GBCs and neurons in the LE generate aAPs with indistinguishable electrical properties. aAP GBCs showed higher cell-cell interactions. We find aAP GBCs to express reduced proliferation signaling compared to no-aAP GBCs, suggesting a non-dividing and potentially more plastic cell state. These findings point to the electrical-active GBCs as an important attribute of the LE, linking the electrophysiological properties with functional implications, and implicate an active role of electrophysiological changes of GBCs in tumor pathophysiology.

cancer biology↗

bioRxiv2023

A multi-strategy antimicrobial discovery approach reveals new ways to combat Chlamydia

While the excessive use of broad-spectrum antibiotics is a major driver of the global antibiotic resistance crisis, more selective therapies remain unavailable for the majority of bacterial pathogens. This includes Chlamydia spp., which cause millions of urogenital, ocular, and respiratory infections each year. We here report major conceptual additions to the available toolkit for antichlamydial discovery, including both experimental and computational approaches. Moreover, we report the to date most comprehensive search of the chemical space for novel antichlamydial activities, which identified over sixty compounds that are chemically diverse, structurally different from known antibiotics, non-toxic to human cells, and highly potent in blocking Chlamydia growth. While some compounds caused a reversible block in Chlamydia development, others could eradicate both established and persistent infections in a bactericidal manner. The most potent antichlamydials displayed compelling selectivity, some also synergies with clinically used antibiotics, as well as interactions profiles enabling predictions of molecular modes of action. Moreover, one compound displayed reduced antichlamydial efficacy in autophagy-deficient cells, suggesting a host- targeted activity. Altogether, we suggest that these novel antichlamydials could serve as tools for advancing our understanding of Chlamydia biology and as chemical starting points for developing more sustainable therapeutics for one of the most successful groups of intracellular pathogens.

microbiology↗

bioRxiv2022

Characterizing amblyopic perception under naturalistic viewing conditions

Current assessments of interocular interactions in amblyopia use rivalrous stimuli, with conflicting stimuli in each eye, which does not reflect vision under typical circumstances. Here we measure interocular interactions in observers with amblyopia, strabismus with equal vision, and controls using a non-rivalrous stimulus. Observers used a joystick to continuously report perceived contrast of dichoptic grating stimuli, identical except that the stimulus was contrast-modulated independently in each eye over time. Consistent with previous studies, a model predicting the time-course of perceived contrast found increased amblyopic eye attenuation, and reduced contrast normalization of the fellow eye by the amblyopic eye, in amblyopic participants compared to controls. However, these suppressive interocular effects were weaker than those found in previous studies, suggesting that rivalrous stimuli may overestimate the effects of amblyopia on interocular interactions during naturalistic viewing conditions.

neuroscience↗

bioRxiv2022

The Chlamydia protein CpoS modulates the inclusion microenvironment and restricts the interferon response by acting on Rab35

The obligate intracellular bacterium Chlamydia trachomatis inserts into the membrane of its vacuole (the inclusion) a family of poorly characterized Inc proteins. While the Inc CpoS was recently revealed as a critical suppressor of host cellular immune surveillance, the underlying mechanism remained unknown. By complementing a cpoS mutant with modified variants of CpoS, we found that CpoS blocks distinct cellular defense responses through distinct mechanisms. Specifically, we show that the ability of CpoS to interact with Rab GTPases is not only instrumental to its ability to mediate lipid transport to the inclusion, but also key to CpoS-mediated inhibition of type I interferon responses. Indeed, depletion of Rab35 can phenocopy the respective defect of the cpoS mutant. Unexpectedly, we found that CpoS is also essential for the formation of inclusion microdomains that control the spatial organization of multiple Incs involved in signaling and modulation of the host cellular cytoskeleton. Overall, our findings highlight the modulation of membrane trafficking as a pathogenic immune evasion strategy and the role of Inc-Inc interactions in shaping the inclusion microenvironment.

microbiology↗

bioRxiv2020

Wasp controls oriented migration of endothelial cells to achieve functional vascular patterning

Endothelial cell migration and proliferation are essential for the establishment of a hierarchical organization of blood vessels and optimal distribution of blood. However, how these cellular processes are coordinated remains unknown. Here, using the zebrafish trunk vasculature we show that in future veins endothelial cells proliferate more than in future arteries and migrate preferentially towards neighboring arteries. In future arteries endothelial cells show a biphasic migration profile. During sprouting cells move away from the dorsal aorta, during remodelling cells stop or move towards the feeding aorta. The final morphology of blood vessels is thus established by local proliferation and oriented cell migration to and from neighboring vessels. Additionally, we identify WASp to be essential for this differential migration. Loss of WASp leads to irregular distribution of endothelial cells, substantially enlarged veins and persistent arteriovenous shunting. Mechanistically, we report that WASp drives the assembly of junctional associated actin filaments and is required for junctional expression of PECAM-1. Together, our data identify that functional vascular patterning in the zebrafish trunk utilizes differential cell movement regulated by junctional actin, and that interruption of differential migration may represent a pathomechanism in vascular malformations.

developmental biology↗

bioRxiv2020

Vasohibin-1 mediated tubulin detyrosination selectively regulates secondary sprouting and lymphangiogenesis in the zebrafish trunk

Previous studies have shown that Vasohibin-1 (Vash-1) is stimulated by VEGFs in endothelial cells and that its overexpression interferes with angiogenesis in vivo. Recently, Vasohibin-1 was found to mediate tubulin detyrosination, a post-translational modification that is implicated in many cell functions, such as cell division. Here we used the zebrafish embryo to investigate the cellular and subcellular mechanisms of Vash-1 on endothelial microtubules during formation of the trunk vasculature. We show that microtubules within venous-derived secondary sprouts are strongly and selectively detyrosinated in comparison with other endothelial cells, and that this difference is lost upon vash-1 knockdown. Vasohibin-1 depletion in zebrafish specifically affected secondary sprouting from the posterior cardinal vein, increasing both the number of sprouts and endothelial cell divisions. We show that altering secondary sprout numbers and structure upon vash-1 depletion leads to a failure in the development and specification of lymphatic vessels of the zebrafish trunk. SUMMARYVasohibin-1 mediated detyrosination of endothelial microtubules is selectively required for adequate behaviour of venous secondary sprouting and subsequent formation of functional lymphatics in the zebrafish trunk.

developmental biology↗

bioRxiv2020

Discovery of a hidden transient state in all bromodomain families

Bromodomains (BDs) are small protein modules that interact with acetylated marks in histones. These post-translational modifications are pivotal to regulate gene expression, making BDs promising targets to treat several diseases. While the general structure of BDs is well known, their dynamical features and their interplay with other macromolecules are poorly understood, hampering the rational design of potent and selective inhibitors. Here we combine extensive molecular dynamics simulations, Markov state modeling and structural data to reveal a novel and transiently formed state that is conserved across all BD families. It involves the breaking of two backbone hydrogen bonds that anchor the ZA-loop with the A helix, opening a cryptic pocket that partially occludes the one associated with histone binding. Our results suggest that this novel state is an allosteric regulatory switch for BDs, potentially related to a recently unveiled BD-DNA binding mode.

biophysics↗

bioRxiv2020

Structural and functional characterization of the Severe fever with thrombocytopenia syndrome virus L protein

The Bunyavirales order contains several emerging viruses with high epidemic potential, including Severe fever with thrombocytopenia syndrome virus (SFTSV). The lack of medical countermeasures, such as vaccines and antivirals, is a limiting factor for the containment of any virus outbreak. To develop such antivirals a profound understanding of the viral replication process is essential. The L protein of bunyaviruses is a multi-functional and multi-domain protein performing both virus transcription and genome replication and, therefore, would be an ideal drug target. We established expression and purification procedures for the full-length L protein of SFTSV. By combining single-particle electron-cryo microscopy and X-ray crystallography, we obtained 3D models covering [~]70% of the SFTSV L protein in the apo-conformation including the polymerase core region, the endonuclease and the cap-binding domain. We compared this first L structure of the Phenuiviridae family to the structures of La Crosse peribunyavirus L protein and influenza orthomyxovirus polymerase. Together with a comprehensive biochemical characterization of the distinct functions of SFTSV L protein, this work provides a solid framework for future structural and functional studies of L protein-RNA interactions and the development of antiviral strategies against this group of emerging human pathogens.

biochemistry↗