Biology subjects

Weidinger, G.

Publications and source records attributed to Weidinger, G..

15 recordsLinked to original sources

bioRxiv2026

Blastema cells exhibit intrinsic migratory capacity but fail to induce osteoblast off-bone migration during Zebrafish fin regeneration

Zebrafish bone regeneration is a highly efficient process, enabling the complete restoration of an amputated fin within few weeks. The hallmark of this epimorphic regeneration is the formation of a blastema atop of a bony fin ray. Osteoblasts near the injury site dedifferentiate and migrate off the bone to contribute to the developing blastema. We show that an injury or a blastema alone is not sufficient to trigger off-bone migration of osteoblasts. Surprisingly, we found that blastema cells themselves possess intrinsic migratory properties. Moreover, when multiple injury sites are present, a preferential distal migration could be observed. We conclude that multiple injuries are hierarchical organized, and that injuries with the highest regenerative potential take priority.

developmental biology↗

bioRxiv2026

A tight balance of anabolic mTORC1 signaling and catabolic autophagic activity regulates zebrafish heart regeneration

Zebrafish can regenerate the heart by proliferation of cardiomyocytes. While the innate immune response and wound re-vascularization are pre-requisites for cardiomyocyte regeneration, little is known about signals linking early injury responses with the initiations of regenerative programs in cardiomyocytes. Here we show that mTOR (mechanistic target of rapamycin) signaling is rapidly activated in response to heart injury in many cell types of the heart including endothelial cells, cardiomyocytes and macrophages, but surprisingly not in neutrophils. We find that mTORC2 regulates macrophage recruitment to the wound, while mTORC1 is required for wound debris clearance by macrophages. In addition, mTOR signaling is required for wound re-vascularization. Interestingly, it also appears to directly regulate cardiomyocyte dedifferentiation and proliferation, making mTOR signaling a central hub for regenerative responses. Anabolic mTOR signaling acts as potent inhibitor of catabolic autophagy in many systems. Yet, we observed upregulation of autophagy within border zone cardiomyocytes where mTOR signaling is active. We show that mTOR signaling limits, but does not block autophagy, and that autophagic flux is regulated by both inhibitory mTOR signaling and stimulatory JNK and MEK pathways. Our results indicate that a fine-balanced anabolic and catabolic injury response is essential for zebrafish heart regeneration. Furthermore, they reveal interesting differences in the regulation of mTOR signaling and autophagy between the regenerative zebrafish heart and non-regenerative mammalian hearts.

developmental biology↗

bioRxiv2026

Genetically interacting mutations and mechanical stress affect the stochasticity of developmental eye defects in yap1 mutants

Congenital abnormalities of eye formation show remarkably variable penetrance with phenotypes even varying between left and right eyes. Here we explore this phenomenon through analysis of the mechanistic basis of low penetrance retinal coloboma in zebrafish yap1nl13/nl13 mutants and identification of factors that modify the probability of this phenotype. We find that the low penetrance stochastically occurring coloboma in yap1nl13/nl13 mutants is due to rupture in the ventral retina at the point of apposition of the lips of the closing choroid fissure and that provision of wild-type Yap in the retinal pigment epithelium suppressed this phenotype. Decreasing actomyosin contractility increased the penetrance of coloboma whereas increasing myosin phosphorylation rescued the phenotype suggesting that altered mechanical properties of the RPE sensitize the eye to stochastic failure of choroid fissure closure. Genetic interaction screening revealed enhanced and synthetic eye phenotypes in yap1nl13/nl13mutants upon abrogation of function of genes encoding extracellular matrix and other genes implicated in eye formation. Our data reveal that the variable penetrance of congenital eye abnormalities can be due to genetic and environmental factors impacting the stochastic variability inherent in the developmental processes underlying eye morphogenesis.

developmental biology↗

bioRxiv2026

Laudanosine restricts Ebola virus entry by targeting TPC2-dependent endolysosomal trafficking

Late endosome-dependent viruses, including filo- and arenaviruses, rely on host endolysosomal trafficking for productive infection. Here, we used a dual-colour Vesicular stomatitis virus (VSV) based pseudoparticle screen of CytoSorb-derived fractions to identify inhibitors of the Zaire Ebolavirus glycoprotein (GP)-mediated entry. Iterative chromatographic purification and mass spectrometry identified Laudanosine, a degradation product of the clinically used neuromuscular blocker Atracurium, as the antiviral compound. Laudanosine specifically inhibited entry mediated by Ebola, Marburg, Lymphocytic choriomeningitis and Lassa virus glycoproteins without affecting VSV-G-dependent entry. Importantly, Laudanosine inhibited authentic Ebola virus infection without detectable cytotoxicity in cell culture and embryonic zebrafish. Molecular dynamics simulations suggest stable association of Laudanosine with the allosteric inhibitory pocket of the lysosomal two-pore channel (TPC2). Consistently, Laudanosine impairs autophagic flux and disrupts endolysosomal trafficking. Together, our findings identify Laudanosine as a previously unrecognised inhibitor of TPC2-dependent entry of highly lethal viral pathogens.

microbiology↗

bioRxiv2026

Molecular Basis of Angicin Activity

Angicin is a class IId bacteriocin produced by Streptococcus anginosus with activity against Gram-positive pathogens, including Listeria monocytogenes and vancomycin-resistant Enterococcus faecium. While the mannose phosphotransferase system (Man-PTS) has been identified as a receptor in L. monocytogenes, its role in streptococci and the structural determinants of Angicin activity remain unclear. Here, we demonstrate that the Man-PTS is required for Angicin susceptibility in Streptococcus constellatus. A transposon mutant (manM::ISS1) showed complete resistance to Angicin and impaired mannose utilization. Structure-activity relationship analysis of truncated and modified peptides localized antimicrobial activity to the C-terminal region, although none of the variants matched the activity of the full-length peptide. Angicin induced membrane depolarization and pore formation in target bacteria. Residual activity in Man-PTS-impaired L. monocytogenes suggests an additional receptor-independent effect at higher concentrations. In vivo toxicity analysis using zebrafish embryos showed low toxicity at active concentrations. These findings identify the Man-PTS as a receptor for Angicin in streptococci and define structural features associated with its antimicrobial activity.

microbiology↗

bioRxiv2025

Wnt/β-catenin signaling promotes zebrafish osteoblast dedifferentiation by wnt10a-mediated inhibition of NF-κB

Dedifferentiation of mature cells is an essential mechanism of source cell formation for regeneration of many systems, including the zebrafish fin. Here, we use bulk and single cell RNASeq to show that osteoblast injury responses involve rapid and extensive transcriptional reprogramming, yielding a cell state that shares characteristics with embryonic osteoblasts, but also expresses many regeneration-specific genes. One gene characterizing this state is the canonical Wnt ligand wnt10a. Using genetic and transgenic perturbations, we demonstrate that wnt10a-dependent Wnt/{beta}-catenin signaling cell-autonomously induces osteoblast dedifferentiation. Loss of wnt10a or of Wnt/{beta}-catenin activity blocks the dedifferentiation program, whereas wnt10a overexpression enhances dedifferentiation and is sufficient to induce it even without injury. Wnt/{beta}-catenin signaling promotes dedifferentiation by suppressing NF-{kappa}B activity, placing it upstream of known cues whose loss causes dedifferentiation. Notably, wnt10a overexpression also stimulates cardiomyocyte dedifferentiation during zebrafish heart regeneration, revealing a conserved role in activating source-cell formation during regeneration.

developmental biology↗

bioRxiv2025

Replication-competent SIVcpz CRISPR screen identifies barriers to successful cross-species transmission

Simian immunodeficiency viruses (SIVs) have crossed from apes to humans at least four times, but only one event gave rise to the AIDS pandemic. The host barriers that pandemic HIV-1 group M (major) strains overcame to spread efficiently in humans remain poorly understood. To identify such barriers, we performed CRISPR-Cas9 screens driven by the replication efficiency of SIVcpz, the chimpanzee precursor of HIV-1. Guide RNA libraries targeting more than 500 human genes encoding potential antiviral factors were inserted into the replication-competent SIVcpz MB897 molecular clone, which is phylogenetically closely related to HIV-1 group M strains. Propagation in Cas9-expressing human SupT1 T cells significantly enriched for sgRNAs targeting ADAR, AXIN1, CEACAM3, CD72, EHMT2, GRN, HMOX1, HMGA1, ICAM2, CD72, IFITM2, MEFV, PCED1B, SGOL2, SMARCA4, SUMO1 and TMEM173. These hits only partially overlapped with those identified in analogous HIV-1-based screens, indicating virus-specific restriction profiles. Functional analyses confirmed that IFITM2 (interferon-induced transmembrane protein 2), PCED1B (PC-esterase domain-containing protein 1B), MEFV (Mediterranean fever protein, pyrin/TRIM20), and AXIN1 (Axis inhibition protein 1), restrict replication of SIVcpz but not of HIV-1 group M strains in primary human CD4 T cells. These findings reveal previously unrecognized host factors that limit SIVcpz replication in human cells and highlight barriers that HIV-1 likely overcame during its adaptation for pandemic spread. One Sentence SummaryCRISPR screens with replication-competent SIVcpz identify human antiviral factors limiting efficient viral replication after zoonotic transmission.

immunology↗

bioRxiv2025

A balanced circadian glycolytic rhythm drives cardiomyocyte cell cycle progression during fish heart regeneration.

The ability of heart tissue to repair itself after injury has fascinated scientists for decades1,2. Researchers have long studied the internal body clock, or circadian rhythm, for its role in coordinating daily cycles of metabolism and cell activity3,4, but its relevance to heart repair has remained unknown. This study explores, for the first time, whether natural daily rhythms influence heart regeneration--a process driven by cardiomyocyte proliferation. We discovered that DNA replication, mitosis, oxidative phosphorylation, and glycolysis follow a precise daily order in regenerating zebrafish hearts. Disrupting core clock gene expression abolishes the rhythms of glycolysis and mitosis, preventing cardiomyocyte cell cycle progression and regeneration. Insulin-resistant Astyanax mexicanus cavefish, which have adapted to dark caves, similarly show a loss of mitosis rhythm and cardiomyocyte cell cycle progression, which we find is caused by reduced glycolysis. Despite this reduction, glycolysis rhythm displays a larger amplitude in cavefish--a pattern recapitulated in insulin-resistant zebrafish. Insulin resistance resets metabolic rhythms to the morning, which is equally detrimental to regeneration. Here, we show that successful cardiac regeneration depends on synchronised clock and glucose rhythms, which together orchestrate the cell cycle events essential for cardiomyocyte proliferation and tissue repair.

physiology↗

bioRxiv2025

ReaxFF-guided Optimisation of VIRIP-based HIV-1 Entry Inhibitors

Peptides hold great promise for safe and effective treatment of viral infections. However, their use is often constrained by limited efficacy and high production costs, especially for long or complex peptide chains. Here, we used ReaxFF molecular dynamics (MD) simulations to optimize the size and activity of VIRIP (Virus Inhibitory Peptide), a naturally occurring 20-residue fragment of 1-antitrypsin that binds the HIV-1 GP41 fusion peptide (FP), thereby blocking viral fusion and entry into host cells. Specifically, we used the NMR structure of the complex between an optimized VIRIP derivative (VIR-165) and the HIV-1 gp41 FP for ReaxFF-guided in silico analysis, evaluating the contribution of each amino acid in the interaction of the inhibitor with its viral target. This approach allowed us to reduce the size of the HIV-1 FP inhibitor from 20 to 10 amino acids (2.28 to 1.11 kDa). HIV-1 infection assays showed that the size-optimized VIRIP derivative (soVIRIP) retains its broad-spectrum anti-HIV-1 capability and is non-toxic in the vertebrate zebrafish model. Compared to the original VIRIP, soVIRIP displayed more than 100-fold higher antiviral activity (IC50 of [~]120 nM). Thus, it is more potent than a dimeric 20-residue VIRIP derivative (VIR-576) that was proven safe and effective in a phase I/II clinical trial. Our results show that ReaxFF-based MD simulations represent a suitable approach for the optimization of therapeutic peptides.

molecular biology↗

bioRxiv2024

BMP signaling promotes heart regeneration via alleviation of replication stress

One hallmark of aging is a decline in tissue regeneration, which can be caused by DNA replication stress. Whether highly regenerative species like zebrafish are immune from such hindrances to replication is unknown. In contrast to most mammals, adult zebrafish achieve complete heart regeneration via cell cycle entry and proliferation of mature cardiomyocytes. We found that cycling cardiomyocytes experience replication stress, which is induced by the demands of regeneration, but does not occur during physiological heart growth. Since zebrafish cardiomyocyte regeneration is remarkably efficient, heart regeneration appears to depend on elevated capabilities to overcome replication stress. Indeed, pharmacological inhibition of ATM and ATR kinases revealed that DNA damage response signaling is essential for heart regeneration. Using inducible overexpression of ligands and inhibitors of the Bone Morphogenetic Protein (BMP)-Smad pathway, combined with analysis of genetic mutants, we found that BMP signaling alleviates cardiomyocyte replication stress. In the absence of BMP signaling, cardiomyocytes become arrested in the S-phase of the cell cycle, which prevents progression to mitosis and results in heart regeneration failure. Interestingly, BMP signaling can also rescue neonatal mouse cardiomyocytes and human fibroblasts from hydroxyurea-induced replication stress. DNA fiber spreading assays in human cancer cells and human hematopoietic stem and progenitor cells (HSPCs) indicate that BMP signaling acts directly on replication dynamics by accelerating DNA replication fork progression and by facilitating their re-start after replication stress-induced stalling. Our results identify the ability to overcome replication stress as key factor for the elevated heart regeneration capacity in zebrafish. Notably, the conserved capability of BMP signaling to promote stress-free DNA replication might unlock new avenues towards anti-aging and pro-regenerative applications in humans.

developmental biology↗

bioRxiv2023

BMP7 promotes cardiomyocyte regeneration

Zebrafish has a remarkable and lifelong ability for cardiac regeneration after severe damage, whereas mammals lose their innate capacity for heart regeneration during early postnatal development. This study aimed to investigate whether the decreased production of growth factors during postnatal mammalian development contributes to the exit of cardiomyocytes from the cell cycle and the reduction in cardiac regenerative ability. We identified growth factors with declining expression levels during early postnatal life in the mouse model and assessed the pro-proliferative ability of these factors on neonatal murine primary cardiomyocytes in vitro. Our findings confirmed the previously reported pro-proliferative effects of NRG1, IL1b, RANKL, IGF2 and IL6, while also identifying novel potential pro-regenerative growth factors. Among them, BMP7 exhibited the most pronounced efficacy. Bmp7 knockdown interfered with the proliferation of neonatal mouse cardiomyocytes in culture and adult bmp7 mutant zebrafish displayed reduced cardiomyocyte proliferation during heart regeneration, indicating that Bmp7 is crucial for cardiomyocyte proliferation in the regenerative stages of mouse and zebrafish hearts. Conversely, bmp7 overexpression was sufficient to boost cardiomyocyte cycling in regenerating zebrafish hearts, while BMP7 administration stimulated mouse cardiomyocyte cycling at postnatal-day-7, when cardiomyocytes ceased to proliferate, and enhanced cardiomyocyte regeneration in vivo in adult mice following myocardial infarction. Mechanistically, BMP7-induced proliferation was mediated by type I BMP receptors BMPR1A and ACVR1, and type II receptors ACVR2A and BMPR2. Downstream signalling involved SMAD5, ERK and AKT. In conclusion, the administration of BMP7 holds promise as a strategy to stimulate heart regeneration following cardiac injury.

molecular biology↗

bioRxiv2022

Zebrafish fin regeneration requires generic and regeneration-specific responses of osteoblasts to trauma

Successful regeneration requires the coordinated execution of multiple cellular responses to injury. In amputated zebrafish fins, mature osteoblasts dedifferentiate, migrate towards the injury and form proliferative osteogenic blastema cells. We show that osteoblast migration is preceded by cell elongation and alignment along the proximodistal axis, which require actomyosin, but not microtubule turnover. Surprisingly, osteoblast dedifferentiation and migration can be uncoupled. Using pharmacological and genetic interventions, we found that NF-{kappa}B and retinoic acid signalling regulate dedifferentiation without affecting migration, while the complement system and actomyosin dynamics are required for migration but not dedifferentiation. Furthermore, by removing bone at two locations within a fin ray, we established a trauma model containing two injury sites. We found that osteoblasts dedifferentiate at and migrate towards both sites, while accumulation of osteogenic progenitor cells and regenerative bone formation only occur at the distal-facing injury. Together, these data indicate that osteoblast dedifferentiation and migration represent generic injury responses that are differentially regulated and can occur independently of each other and of regenerative growth. Successful bone regeneration appears to require the coordinated execution of generic and regeneration-specific responses of osteoblast to trauma. O_FIG O_LINKSMALLFIG WIDTH=131 HEIGHT=200 SRC="FIGDIR/small/481466v1_ufig1.gif" ALT="Figure 1"> View larger version (67K): org.highwire.dtl.DTLVardef@c1145org.highwire.dtl.DTLVardef@41f525org.highwire.dtl.DTLVardef@4569eaorg.highwire.dtl.DTLVardef@12c85e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2020

Biomolecular models of EPI-X4 binding to CXCR4 allow the rational optimization of peptides with therapeutic potential

The Endogenous Peptide Inhibitor of CXCR4 (EPI-X4) is a body-own fragment of albumin and specific antagonist of the CXC-motif-chemokine receptor 4 (CXCR4). CXCR4 signaling is induced by its sole chemokine ligand CXCL12 and is involved in a plethora of functions including cell homing, differentiation, survival and angiogenesis. Consequently, dysregulation of CXCR4 is involved in a variety of disorders, such as cancer or inflammatory diseases, making CXCR4 an attractive drug target. EPI-X4 and derivatives with increased CXCR4 binding affinities represent promising leads as CXCR4 antagonists and have shown therapeutic activity in mouse models of inflammatory diseases. However, it is currently unclear how EPI-X4 and its derivatives interact with CXCR4. Here, by combining biomolecular simulations with experimental mutagenesis and activity studies we investigated the binding behavior of EPI-X4 to CXCR4 at the molecular level. Our work allowed us to show that the EPI-X4 peptide interacts primarily in the minor pocket of CXCR4 through its N-terminal residues. The biomolecular interactions highlighted by the computational studies are in good agreement with the experimental mutagenesis data. Moreover, we found that the N-terminal seven amino-acids of EPI-X4 (a 16-mer) and its improved derivatives (12-mers) are sufficient for CXCR4 binding, which led to the development of shorter leads with optimized CXCR4 antagonizing properties. Collectively, we here established how EPI-X4 binds to its receptor and used this knowledge for rational drug design. The new peptide variants developed by us are more potent in terms of inhibiting CXCR4-downstream signaling and cancer cell migration, without toxic effects.

molecular biology↗

bioRxiv2020

Is zebrafish heart regeneration complete? Lineage-restricted cardiomyocytes proliferate to pre-injury numbers but some fail to differentiate in fibrotic hearts

Adult zebrafish are frequently described to be able to "completely" regenerate the heart. Yet, the extent to which cardiomyocytes lost to injury are replaced is unknown, since only indirect or non-quantitative evidence for cardiomyocyte proliferation exists. We established stereological methods to quantify the number of cardiomyocytes at several time-points post cryoinjury. Intriguingly, after cryoinjuries that killed about 1/3 of the ventricular cardiomyocytes, pre-injury cardiomyocyte numbers were restored already within 30 days. Yet, many hearts retained small residual scars, and a subset of cardiomyocytes bordering these fibrotic areas remained smaller, lacked differentiated sarcomeric structures, and displayed defective calcium signaling. Thus, a subset of regenerated cardiomyocytes failed to fully mature. While lineage-tracing experiments have shown that regenerating cardiomyocytes are derived from differentiated cardiomyocytes, technical limitations have previously made it impossible to test whether cardiomyocyte trans-differentiation contributes to regeneration of non-myocyte cell lineages. Using Cre responder lines that are expressed in all major cell types of the heart, we found no evidence for cardiomyocyte transdifferentiation into endothelial, epicardial, fibroblast or immune cell lineages. Overall, our results imply a refined answer to the question whether zebrafish can completely regenerate the heart: in response to cryoinjury, preinjury cardiomyocyte numbers are indeed completely regenerated, while restoration of cardiomyocyte differentiation and function, as well as resorption of scar tissue, is less robustly achieved.

developmental biology↗

bioRxiv2020

An optimized derivative of an endogenous CXCR4 antagonist prevents atopic dermatitis and airway inflammation

BackgroundAberrant CXCR4/CXCL12 signaling is involved in many pathophysiological processes including chronic inflammatory diseases. Thus, the chemokine receptor CXCR4 is a promising target for the therapy of inflammatory disorders, such as atopic dermatitis or allergic asthma. A natural fragment of serum albumin, named EPI-X4, has previous been identified as endogenous peptide antagonist and inverse agonist of CXCR4. The endogenous CXCR4 antagonist provides a promising basis for the development of improved analogues for the therapy of inflammatory diseases. ObjectiveTo increase the anti-CXCR4 activity of EPI-X4 and to evaluate the therapeutic potential of optimized analogs in mouse models of atopic dermatitis and asthma. MethodsMolecular docking analysis of the interaction of EPI-X4 with CXCR4 was performed to define critical interaction motifs and to rationally design analogs with increased activity. EPI-X4 derivatives were synthesized and CXCR4 binding and antagonizing activity determined in assays for antibody competition, inhibition of CXCR4-mediated HIV-1 infection, CXCL12-dependent Ca2+ mobilization, ERK and AKT phosphorylation and cell migration. Toxicity of peptides was evaluated in zebrafish embryos. The therapeutic efficacy of the lead peptide EPI-X4 JM#21 was determined in mouse models of atopic dermatitis and asthma. ResultsDocking analysis identified key interaction motifs of EPI-X4/CXCR4. Rational drug design allowed to increase the anti-CXCR4 activity of EPI-X4 and resulted in the generation of the lead analog JM#21, which bound CXCR4 and suppressed CXCR4-tropic HIV-1 infection more efficiently than the clinically approved small molecule CXCR4 antagonist AMD3100. JM#21 did not exert toxic effects in zebrafish embryos and efficiently prevented inflammation of the skin in a mouse model of atopic dermatitis. Moreover, EPI-X4 and its improved derivative suppressed allergen-induced infiltration of eosinophils and other immune cells into the airways of animals in an asthma mouse model. ConclusionThe rationally designed EPI-X4 derivative JM#21 is a potent antagonist of CXCR4 and the first CXCR4 inhibitor with therapeutic efficacy in atopic dermatitis. Further clinical development of this new class of CXCR4 antagonists for the therapy of atopic dermatitis, asthma and other CXCR4-associated diseases is highly warranted. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

immunology↗