Biology subjects

Weinberger, F.

Publications and source records attributed to Weinberger, F..

13 recordsLinked to original sources

bioRxiv2026

How wind and currents shape the drift velocity of macrophytes and macroplastic particles - from experiment to model

The post-detachment drifting phase of macrophytes, during which they can be alive, dead, or senescent, plays a crucial ecological and biogeochemical role by influencing long-range dispersal, transporting rafting species, affecting carbon sequestration, promoting blooms, and leading to beaching events. In order to predict the dispersal of macrophytes and macroplastic particles and where they will affect the ecosystem, it is important to be able to model how their drift velocities are influenced by hydrodynamic and aerodynamic factors. In this study, we investigated the drift velocity of macrophytes with diverse morphologies and macroplastic particles in a racetrack flume under different current conditions, in combination with and without wind in the same direction as the water current. Our data show that the drift velocity of macrophytes is highly dependent on their buoyancy and affected by morphological characteristics. Wind increased the velocity of the surface water, which in turn increased the drift velocity of both macrophytes and macroplastic particles. However, wind-induced turbulences reduced the overall effect, especially for macrophytes, which protruded minimally above the water surface in comparison to macroplastic particles. For positively buoyant specimens, an existing particle model was experimentally confirmed to predict macrophyte and macroplastic particle drift velocities reliably, irrespective of shape. For negatively buoyant species, we propose a novel equation to predict drift velocity, incorporating the diverse shapes of macrophytes, as well as their interaction with the bottom. These results represent the first step toward the development of trait-based models that represent macrophytes more realistically in dispersal simulations. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=135 SRC="FIGDIR/small/709487v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1ab9f6aorg.highwire.dtl.DTLVardef@6ef75dorg.highwire.dtl.DTLVardef@132334forg.highwire.dtl.DTLVardef@c6a3d8_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2025

Contractility governs cardiomyocyte cell cycle activity

The hearts rhythmic contractions keep blood flowing to deliver the oxygen and nutrients that sustain life, but this very strength may also explain why the heart has so little capacity to regenerate. Whereas embryonic and neonatal hearts can repair themselves, this ability is rapidly lost after birth as heart muscle cells (cardiomyocytes) exit the cell cycle. We tested whether the force-generating machinery of the heart acts as a barrier to regeneration. Across human cardiomyocytes, engineered heart tissue, and myocardial slices, we found that active force generation suppresses proliferation, whereas its inhibition, through chemogenetic or pharmacological modulation, enabled cell cycle re-entry. These findings identify contractility as a central regulator of regenerative potential, highlighting new directions for strategies to restore repair in the diseased heart.

cell biology↗

bioRxiv2025

Sedimentation and drag in drifting macrophytes and plastic objects: A model

Predicting macroalgal sedimentation and drag sensitivity is essential for ecological and geochemical modeling, and for optimizing seaweed cultivation. However, despite the diversity of macrophyte forms, models incorporating their specific morphology and hydrodynamic effects are largely lacking. To develop a broadly applicable model, we tested whether the drag response of diverse macrophyte morphologies and plastic objects can be accurately predicted by approximating them as ellipsoids and accounting for their specific shapes. A set of simple shape descriptors (wet weight, volume, thallus thickness, thallus projection area) and an empirical solution for the drag equation, enabled relative accurate predictions of the sinking velocity for 26 morphologically diverse macroalgae species, as well as the eelgrass Zostera marina, another major source of drifting biomass in many shallow seas. Additionally, we identified a second simpler empirical solution that incorporates shape and, while slightly less accurate, can be applied to a broader range of particles, including plastics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/651208v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@184bf04org.highwire.dtl.DTLVardef@18dce9org.highwire.dtl.DTLVardef@4f5b9dorg.highwire.dtl.DTLVardef@7aad5_HPS_FORMAT_FIGEXP M_FIG Graphical abstract C_FIG

ecology↗

bioRxiv2024

Greater host influence and promiscuity: How an invasive seaweed host has advantages over co-occurring natives

The surface microbiome of seaweed hosts is a multi-domain biofilm regulated by host-microbe and microbe-microbe interactions. The extent to which hosts influence these interactions, and potentially affect their resilience and invasion success, remains unclear. We experimentally tested whether hosts with invasion history exert more influence over their biofilms than native hosts. Biofilm formation on proxy surfaces adjacent to one invasive (Gracilaria vermiculophylla) and two native (Fucus serratus, Fucus vesiculosus) co-occurring hosts was monitored and compared to mature epiphytic biofilms of the same hosts. Only Gracilarias proxy biofilms were significantly different in community composition compared to control surfaces. Gracilarias proxy biofilms also showed the highest similarity to their adjacent algae sharing certain bacterial taxa that were absent in control treatments, indicating that colonization of the proxy surface was influenced by the host. Gracilaria and its proxy biofilm showed highest similarity in microbial network variables, suggesting a higher ability of the invader to influence connectivity and microbial associations within its biofilm. Meanwhile Gracilarias mature biofilm also showed higher variability in its prokaryotic composition over experiments, which was also reflected in a less robust microbial network in both Gracilaria and its proxy biofilms. This suggests that in addition to stronger influence in the invasive host, it was also more promiscuous towards potential symbionts from the environment. Ultimately, through examining microbial interactions, in line with previous research we found that host influence and promiscuity may play an important role in seaweed hosts to acclimate to different environmental condition and successfully thrive in new ecosystems.

molecular biology↗

bioRxiv2024

Seasonal cycles in a seaweed holobiont: A multiyear time series reveals repetitive microbial shifts and core taxa

Seasonality is an important natural feature that drives cyclic environmental changes. Seaweed holobionts, inhabiting shallow waters such as rocky shores and mud flats, are subject to seasonal changes in particular, but little is known on the influence of seasonality on their microbial communities. In this study, we conducted a bi-monthly, three-year time series to assess the seasonality of microbial epibiota in the seaweed holobiont Gracilaria vermiculophylla. Our results reveal pronounced seasonal shifts that are both taxonomic and functional, oscillating between late winter and early summer across consecutive years. While epibiota varied taxonomically between populations, they were functionally similar, indicating that seasonal variability drives functional changes, while spatial variability is more redundant. We also identified seasonal core microbiota that consistently (re)associated with the host at specific times, alongside a permanent core that is present year-round, independent of season or geography. These findings highlight the dynamic yet resilient nature of seaweed holobionts and demonstrate that their epibiota undergo predictable changes. Therewith, the research offers important insights into the temporal dynamics of seaweed-associated microbiota, and demonstrates that the relationship between seaweed host and its epibiota is not static, but naturally subject to an ongoing seasonal succession process.

ecology↗

bioRxiv2024

Functional stability despite high taxonomic turnover characterizes the Ulva microbiome across a 2,000 km salinity gradient

The green seaweed Ulva depends on its associated bacteria for morphogenesis and is an important model to study algal-bacterial interactions. Ulva-associated bacteria exhibit high turnover across environmental gradients, leading to the hypothesis that bacteria contribute to the acclimation potential of the host. Yet little is known about the variation in the functional profile of Ulva-associated bacteria in relation to environmental changes. To test which microbial functions shift alongside a strong environmental gradient, we analysed microbial communities of 91 Ulva samples across a 2,000 km Atlantic-Baltic Sea salinity gradient using metagenomic sequencing. Metabolic reconstruction of 639 metagenome-assembled genomes revealed widespread potential for carbon, sulphur, nitrogen, and vitamin metabolism, including amino acid and vitamin B biosynthesis. While salinity explained 70% of taxonomic variation, it only accounted for 17% of functional variation, indicating extensive functional stability. The limited variation was attributed to typical high-salinity bacteria exhibiting enrichment in genes for thiamine, pyridoxal, and betaine biosynthesis. These metabolic modules likely contribute to oxidative stress mitigation, cellular osmotic homeostasis, and membrane stabilization in response to salinity variations. Our results emphasise the importance of functional profiling to understand the seaweed holobiont and its collective response to environmental change.

microbiology↗

bioRxiv2023

Impulse initiation in engrafted pluripotent stem cell-derived cardiomyocytes can stimulate the recipient heart.

Transplantation of pluripotent stem cell-derived cardiomyocytes is a novel promising cell-based therapeutic approach for patients with heart failure. However, engraftment arrhythmias are a predictable life-threatening complication and represent a major hurdle for clinical translation. Catheter-based electrophysiological analysis suggested that the ventricular arrhythmias were caused by an automaticity of the transplanted cells, but whether impulse generation by transplanted cardiomyocytes can propagate to the host myocardium and override the recipient rhythm has not been directly assessed experimentally. We used optogenetics to specifically activate engrafted cardiomyocytes, which resulted in impulse generation in the engrafted cardiomyocytes and stimulated the recipient heart (4/9 hearts). Thus, our study shows that transplanted cardiomyocytes can electrically couple to the host myocardium and stimulate the recipient heart, providing experimental evidence that cardiomyocyte automaticity can serve as a trigger for ventricular arrhythmias.

pharmacology and toxicology↗

bioRxiv2023

THE RHODOEXPLORER PLATFORM FOR RED ALGAL GENOMICS AND WHOLE GENOME ASSEMBLIES FOR SEVERAL GRACILARIA SPECIES

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales are highly diverse and widely distributed order whose species can serve as ecosystem engineers in intertidal habitats, including several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

genomics↗

bioRxiv2022

Immature human engineered heart tissues engraft in a guinea pig chronic injury model

AO_SCPLOWBSTRACTC_SCPLOWEngineered heart tissue (EHT) transplantation represents an innovative, regenerative approach for heart failure patients. Late preclinical trials are underway, and the first clinical trial has started in 2021. Preceding studies revealed functional recovery after implantation of in vitro-matured EHT in the subacute stage while transplantation in a chronic injury setting was less efficient. We hypothesized that the use of immature EHT patches (EHTIm) could improve cardiomyocytes (CM) engraftment. Chronic myocardial injury was induced in a guinea pig model (n=14). EHTIm (15x106 cells) were transplanted directly after casting. Functional consequences were assessed by serial echocardiography. Animals were sacrificed four weeks after transplantation and hearts were excised for histological analysis. Cryo-injury lead to large transmural scars amounting to 26% of the left ventricle. Grafts were identified by a positive staining for human Ku80 and dystrophin, remuscularizing 9% of the scar area on average. The CM density in the graft was higher compared to previous studies with in vitro-matured EHTs and showed a greater population of immature CM. Echocardiographic analysis showed a small improvement of left ventricular function after EHTIm transplantation. In a small translational proof-of-concept study human scale EHTIm patches (4.5x108 cells) were epicardially implanted on healthy pig hearts (n=2). In summary, we provide evidence that transplantation of immature EHT patches without pre-cultivation results in better cell engraftment.

pharmacology and toxicology↗

bioRxiv2021

Contractile force of transplanted cardiomyocytes contributes to heart function after injury

Transplantation of pluripotent stem cell-derived cardiomyocytes represents an innovative therapeutic strategy for heart failure. Studies in small and large animals have demonstrated functional recovery of left ventricular function after cardiomyocyte transplantation1-4, and first clinical studies are currently underway5. Yet, the mechanism of action underlying graft-induced benefit is unknown6. Here we demonstrate that transplanted cardiomyocytes actively contribute to heart function. We transplanted cardiomyocytes with an optogenetic off-on switch in a guinea pig cardiac injury model. Light-induced inhibition of engrafted cardiomyocyte contractility resulted in a rapid decrease of left ventricular function that was fully reversible with the offset of photostimulation. Hence, our optogenetic approach demonstrated that transplanted cardiomyocytes actively participate in heart function, supporting the hypothesis that the delivery of new force-generating myocardium can serve as a regenerative therapeutic strategy.

pharmacology and toxicology↗

bioRxiv2021

Human engineered heart tissue transplantation in a guinea pig chronic injury model

AO_SCPLOWBSTRACTC_SCPLOWMyocardial injury leads to an irreversible loss of cardiomyocytes (CM). The implantation of human engineered heart tissue (EHT) has become a promising regenerative approach. Previous studies exhibited beneficial, dose-dependent effects of human induced pluripotent stem cell (hiPSC)-derived EHT patch transplantation in a guinea pig model in the subacute phase of myocardial injury. Yet, advanced heart failure often results from a chronic remodeling process. Therefore, from a clinical standpoint it is worthwhile to explore the ability to repair the chronically injured heart. In this study human EHT patches were generated from hiPSC-derived CMs (15x106 cells) and implanted epicardially four weeks after injury in a guinea-pig cryo-injury model. Cardiac function was evaluated by echocardiography after a follow-up period of four weeks. Hearts revealed large transmural myocardial injuries amounting to 27% of the left ventricle. EHT recipient hearts demonstrated compact muscle islands of human origin in the scar region, as indicated by a positive staining for human Ku80 and dystrophin, remuscularizing 5% of the scar area. Echocardiographic analysis demonstrated no significant difference between animals that received EHT patches and animals in the control group (fractional area change 36% vs. 34%). Thus, EHT patches engrafted in the chronically injured heart but in contrast to the subacute model, grafts were smaller and EHT patch transplantation did not improve left ventricular function, highlighting the difficulties for a regenerative approach.

pharmacology and toxicology↗

bioRxiv2018

Evidence for minimal cardiogenic potential of Sca-1 positive cells in the adult mouse heart

BackgroundDespite modern pharmacotherapy, heart failure remains a major medical burden. The heart has a limited regenerative capacity, and bolstering regeneration might represent new therapeutic approaches for heart failure patients. Various progenitor cells in the heart have been proposed to have cardiomyogenic properties, but this evidence is based mostly on cell culture and transplantation studies. One population of interest is characterized by the expression of Stem Cell Antigen-1 (Sca-1). Here we tested the hypothesis that Sca-1+ cells are endogenous progenitors for cardiomyocytes in the adult heart.\n\nMethodsWe evaluated the innate cardiogenic potential of Sca-1+ cells in vivo by generating a novel mouse model to genetically lineage-trace the fate of Sca-1 expressing cells. This was accomplished by introducing a tamoxifen-inducible Cre-recombinase into the Sca-1 locus (Sca-1mCm/+). Crossing this mouse line to a Cre-dependent tdTomato reporter line allowed for genetic lineage-tracing of endogenous Sca-1+ cells (Sca-1mCmR26tdTomato). The frequency of Sca-1+ cardiomyocytes was quantified from dispersed cell preparations and confirmed by in situ histology.\n\nResultsWe validated the genetic lineage tracing mouse model in bone marrow and heart. Unlike previous publications suggesting significant cardiogenic potential, we found that less than 0.02% of cardiomyocytes per year were derived from Sca-1+ cells in the adult heart under homeostatic conditions. At six months after myocardial infarction, we found less than 0.01% of cardiomyocytes were derived from Sca-1+ cells.\n\nConclusionOur results show that Sca-1+ cells in the adult heart have minimal cardiogenic potential under homeostatic conditions or in response to myocardial infarction.

cell biology↗

bioRxiv2016

THE IDENTIFICATION OF SOURCE AND VECTOR OF A PROLIFIC MARINE INVADER

The source and vector of an introduced species inform its ecological and evolutionary history and may guide management that seeks to prevent future introductions. Surprisingly, few studies have successfully used genetic tools to independently inform the specific source and pathway of biological invasions. The ecological history of many introduced species, including their origins and vectors, is often based on suppositions or educated guesses. Here, we used mitochondrial and microsatellite genotyping to trace the invasion of the Asian seaweed Gracilaria vermiculophylla (Rhodophyta) along the three coastlines of the Northern Hemisphere to which it has been introduced: the western coast of North America, eastern coast of the United States and the coasts of Europe and northwest Africa. Analyzing 37 native and 53 introduced sites, we identified the Pacific coastline of northeastern Japan as the ultimate source of the Northern Hemisphere invasion. Coincidentally, most exports of the oyster Crassostrea gigas historically originated from this region and both species often grow in close proximity. Based on genetic signatures, each of the three coastlines likely received thalli directly from Japan, as well as material from another introduced coastline (i.e., a secondary invasion). Our ability to document a source region, which was enabled by a robust sampling of locations and loci that previous studies lacked, reflected strong phylogeographic structure along native coastlines. We suggest Gracilaria vermiculophylla is an important representative example of many species likely exported out of Japan by the oyster trade and its genetic signatures that may be a hallmark of oyster introduction legacies.

evolutionary biology↗