Publikationen

Organ injury triggers nonneuronal electric currents essential for regeneration. However, the mechanisms by which electrical signals are generated, sensed, and transmitted upon damage to promote organ growth remain unclear. Here, we uncover that organ repair relies on dynamic electrochemical coupling between membrane potential depolarization and intracellular signaling, essential to activate cell proliferation. By subsecond live imaging of locally injured zebrafish larval fins, we identify events across time and space: a millisecond, long-range, membrane depolarization gradient, followed by second-persistent intracellular calcium responses. In the subsequent hour, voltage sensing phosphatase senses the injury-driven membrane potential change and autonomously translates the electric signal intracellularly, promoting tissue-wide cell proliferation. Connecting these dynamics with an electrodiffusive model showed that ionic fluxes and electric potential become coupled in the fin's interstitial space, enabling organ-wide signal spreading. Our work reveals the coupling between fast electrical signals and slower intracellular signaling, ensuring complete organ recovery.

Subsociality and wood-eating or xylophagy are understood as key drivers in the evolution of eusociality in Blattodea (cockroaches and termites), two features observed in the cockroach genus Cryptocercus, the sister group of all termites. We analyse two high-quality genomes from this genus, C. punctulatus from North America and C. meridianus from Southeast Asia, to explore the evolutionary transitions to xylophagy and subsociality within Blattodea. Our analyses reveal evidence of relaxed selection in both Cryptocercus and termites, indicating that a reduction in effective population size may have occurred in their subsocial ancestors. These findings challenge the expected positive correlation between dN/dS ratios and social complexity, as Cryptocercus exhibits elevated dN/dS values that may exceed those of eusocial termites. Additionally, we infer a reduction in the number of Ionotropic Receptors and a change from uni- to bimodal methylation signatures in protein coding genes in a common ancestor of Cryptocercus and termites, mechanisms previously thought to have evolved with the emergence of eusociality in termites. Future studies incorporating additional genomic data from diverse blattodean species can further build on these findings and provide deeper insights into the molecular mechanisms driving transitions to xylophagy and eusociality.

Organoids derived from pluripotent stem cells have emerged as powerful models to study human development. To investigate signaling pathways regulating human pancreas differentiation and morphogenesis, we developed a high-content, image-based screen and quantitative multivariate analysis pipelines robust to heterogeneity to extract single-cell and organoid features using pancreatic progenitor organoids. Here, we identified 54 compounds affecting cell identity and/or morphological landscape. Focusing on one family of compounds, we found that glycogen synthase kinase 3α/β (GSK3A/B) inhibition via wingless/int-1 (WNT) signaling has a reversible effect on cell identity, repressing pancreatic progenitor markers and inducing a poised state in progenitors transitioning to acinar cells. We show that additional fibroblast growth factor (FGF) repression enables further differentiation of acinar cells, recapitulating pancreatic acinar morphogenesis and function. The ability to produce acinar cells is valuable for future studies on pancreatic exocrine function and cancer initiation in humans, as acinar cells are thought to be an important cell of origin for pancreatic adenocarcinoma.

Multipolar migration is a conserved neuronal migration mode in the developing brain, enabling emerging neurons to navigate in crowded environments and reach precise laminar positions. Yet, how these cells interpret external cues to guide their migration is not fully understood. We investigate this question using retinal horizontal cells as a model. Combining transcriptomics, targeted CRISPR screening, and live imaging, we reveal the spatiotemporal guidance system underlying horizontal cell lamination: repulsive Slit1b/2-Robo2 signaling in the amacrine cell layer initiates apical horizontal cell migration, while attractive neurturin-Gfrα1/2 signaling from photoreceptors fine-tunes final positioning beneath the photoreceptor layer. Disruption of these pathways causes basal retention of horizontal cells, highlighting the importance of spatially coordinated signaling for proper lamination and functional retinal circuitry. Our results uncover how positional signals and tissue architecture cooperate to achieve neuronal migration precision, a principle likely relevant across the developing central nervous system.

Hibernation is an adaptive survival strategy used by animals to cope with extreme environmental conditions. Although this physiological process involves complex metabolic changes, its underlying biological mechanisms remain largely unknown. Through comparative genomic analysis of six hibernating species across five orders, we identified an ancient amino acid substitution in POMT2 (R708Q), exhibiting signals of both convergent and positive selection in hibernating mammals. Phylogenetic analysis using HeIST indicated hemiplasy as a possible explanation, though given mammalian divergence times and the broader evidence for convergence, this is best considered an alternative rather than the primary interpretation. Functional studies using transgenic mice demonstrated the contribution of this mutation to hypoxia adaptation. Notably, despite the absence of this mutation in Rodentia hibernators, we included Graphiurus kelleni as a positive control in physiological studies of transgenic mice carrying POMT2 (R708Q), given its remarkable hypoxia adaptation during hibernation. Our findings not only provide novel insights into the genetic basis of hypoxic adaptation in hibernating mammals but also suggest incomplete lineage sorting (hemiplasy) as a plausible evolutionary mechanism for this important adaptive trait.

Electrochemical gradients are essential to the functioning of cells and form across membranes using active transporters. Here we show in contrast that condensed biomolecular systems-often termed condensates-sustain pH gradients without any external energy input. By studying individual condensates on the micrometre scale using a microdroplet platform, we reveal dense-phase pH shifts towards conditions of minimal electrostatic repulsion. We demonstrate that protein condensates can drive substantial alkaline and acidic gradients, which are compositionally tunable and can extend to complex architectures sustaining multiple unique pH conditions simultaneously. Through in silico characterization of human proteomic condensate networks, we further highlight potential wide-ranging electrochemical properties emerging from condensation in nature, while correlating intracellular condensate pH gradients with complex biomolecular composition. Together, the emergent nature of condensation shapes distinct pH microenvironments, thereby creating a regulatory mechanism to modulate biochemical activity in living and artificial systems.

Through digital imaging, microscopy has evolved from primarily being a means for visual observation of life at the micro- and nano-scale, to a quantitative tool with ever-increasing resolution and throughput. Artificial intelligence, deep neural networks, and machine learning (ML) are all niche terms describing computational methods that have gained a pivotal role in microscopy-based research over the past decade. This Roadmap encompasses key aspects of how ML is applied to microscopy image data, with the aim of gaining scientific knowledge by improved image quality, automated detection, segmentation, classification and tracking of objects, and efficient merging of information from multiple imaging modalities. We aim to give the reader an overview of the key developments and an understanding of possibilities and limitations of ML for microscopy. It will be of interest to a wide cross-disciplinary audience in the physical sciences and life sciences.

Early development across vertebrates and insects critically relies on robustly reorganizing the cytoplasm of fertilized eggs into individualized cells1,2. This intricate process is orchestrated by large microtubule structures that traverse the embryo, partitioning the cytoplasm into physically distinct and stable compartments3,4. Here, despite the robustness of embryonic development, we uncover an intrinsic instability in cytoplasmic partitioning driven by the microtubule cytoskeleton. By combining experiments in cytoplasmic extract and in vivo, we reveal that embryos circumvent this instability through two distinct mechanisms: either by matching the cell-cycle duration to the time needed for the instability to unfold or by limiting microtubule nucleation. These regulatory mechanisms give rise to two possible strategies to fill the cytoplasm, which we experimentally demonstrate in zebrafish and Drosophila embryos, respectively. In zebrafish embryos, unstable microtubule waves fill the geometry of the entire embryo from the first division. Conversely, in Drosophila embryos, stable microtubule asters resulting from reduced microtubule nucleation gradually fill the cytoplasm throughout multiple divisions. Our results indicate that the temporal control of microtubule dynamics could have driven the evolutionary emergence of species-specific mechanisms for effective cytoplasmic organization. Furthermore, our study unveils a fundamental synergy between physical instabilities and biological clocks, uncovering universal strategies for rapid, robust and efficient spatial ordering in biological systems.

Human liver ductal epithelium is morphologically, functionally, and transcriptionally heterogeneous. Under- standing the impact of this heterogeneity has been challenging due to the absence of systems that recapit- ulate this heterogeneity in vitro. Here, we found that human liver cholangiocyte organoids do not retain the complex cellular heterogeneity of the native ductal epithelium. Inspired by the knowledge of the cellular niche, we refined our previous organoid medium to fully capture the in vivo cellular heterogeneity. We em- ployed this refined system to analyze the relationships between human biliary epithelial cell states. In our refined model, cholangiocytes transition toward hepatocyte-like states through a bipotent state. Additionally, inhibiting WNT signaling enhances the differentiation capacity of the cells toward hepatocyte-like states. By capturing the in vivo cholangiocyte heterogeneity, our improved organoid model represents a platform to investigate the impact of the different liver ductal cell states in cell plasticity, regeneration, and disease.

Metabolic dysfunction-associated steatotic liver disease (MASLD) encompasses liver steatosis and metabolic dysfunction-associated steatohepatitis (MASH), which can result in fibrosis and/or cirrhosis and increase the risk of hepatocellular carcinoma (HCC). The latest Clinical Practice Guidelines acknowledge the importance of systemic metabolic dysfunction as a driver of hepatic lipid accumulation and disease progression. To ensure translational relevance of preclinical models, they need to faithfully replicate the key human pathophysiological characteristics of MASLD and its progression to fibrosis and HCC. This Review discusses the strengths and weaknesses of prevalent MASLD and MASH-HCC preclinical models, expanding the discussion to the latest advances in vivo (for example, genetically altered, humanized and large animals) and in vitro (for example, organoids or spheroids, 3D-bioprinted livers, precision-cut liver slices, organs-on-a-chip and decellularized scaffolds). Evidence will be critically re-assessed according to the new MASLD definition, paving a consensus in the field for nomenclature, expected limitations and how to conduct a systematic validation of new models against human-relevant disease outcomes. We also propose a standardized pipeline for preclinical studies in MASLD and MASH-HCC. This Review aims to help researchers make informed decisions when choosing an experimental design that best aligns with the specific requirements of their projects, whilst meaningfully replicating human disease.