Biology subjects

Bun, P.

Publications and source records attributed to Bun, P..

6 recordsLinked to original sources

bioRxiv2026

Temporal tuning of actin nucleation by the repurposed DNA repair complex RAD51/fignl1 encodes distinct axon guidance decisions

Axon guidance is essential for neural circuit assembly and function. While much of the repertoire of guidance cues and receptors is known, its limited diversity cannot fully explain the remarkable complexity of the brain connectome. How temporally ordered, context-dependent intrinsic programs shape the diversity of axonal responses to guidance signals remains poorly understood. We reveal how non-canonical Wnt5a signalling repurposes the DNA repair complex RAD51/fignl1 as a downstream integrator to control retinal ganglion cell axon decision-making at the midline. We demonstrate that differential RAD51/fignl1 expression and interaction dynamics between ipsilateral and contralateral axons tunes the magnitude and temporal dynamics of F-actin nucleation, thereby encoding their trajectory choice. Our findings establish temporal control of cytoskeletal dynamics as a key determinant of axon decision-making and thereby a fundamental layer of circuit wiring. They provide a potential mechanistic framework linking mutations in the DNA repair gene RAD51 to neurodevelopmental disorders with midline guidance defects.

neuroscience↗

bioRxiv2025

Cell-autonomous mitochondrial calcium flux governs oligodendrocyte regeneration

Oligodendrocyte (OL) lineage cells drive central nervous system remyelination, yet the intrinsic mechanisms that define their regenerative potential remain unclear. We identify spontaneous, cell-autonomous intracellular Ca2+ signaling as a critical mechanism regulating OL regeneration following demyelination. Longitudinal in vivo imaging and ex vivo recordings reveal that Ca2+ signaling arises intrinsically within OL lineage cells after demyelination, and occurs independently from neuronal or behavioral activity. Mechanistically, mitochondrial Ca2+ flux sustains intracellular Ca2+ signals in oligodendroglia, and its in vivo disruption impairs oligodendrocyte precursor cell (OPC) proliferation, differentiation, and repopulation at the lesion site. Conversely, enhancing oligodendroglial Ca2+ signaling in vivo using chemogenetics stimulates lineage expansion and differentiation. In primary human OPC cultures, modulation of mitochondrial Ca2+ flux similarly reduces proliferation, indicating a conserved role for this pathway across species. These findings identify mitochondrial Ca2+ flux as a central driver of the oligodendroglial regeneration and a potential therapeutic target in demyelinating diseases.

neuroscience↗

bioRxiv2025

Adhesion to a common ECM mediates interdependence in tissue morphogenesis in Drosophila

For organs to be functional, the cells and tissues that constitute them must effectively interact with each other and coordinate their behaviours. Halfway during Drosophila embryogenesis, two lateral epidermal sheets stretch to fuse at the dorsal midline; concomitant with this, the main tubes of the respiratory system also shift dorsally. Here, we show that these processes occur simultaneously and are coordinated by the adhesion of the epidermal sheets and a subset of cells of the tracheal trunks to a common extracellular matrix (ECM) that separates them. We show that during dorsal closure, tracheal trunk cells extend protrusions towards the ECM underneath the epidermis. These protrusions are under tension, suggesting they have a mechanical function. Additionally, perturbing adhesion between tracheal cells and the epidermis affects the development of both tissues. Altogether, our findings uncover a novel mechanism used for tissue coordination during development, one that is based on tissue adhesion towards a common ECM capable of transmitting forces across the embryo.

developmental biology↗

bioRxiv2022

Versatile and automated workflow for the analysis of oligodendroglial calcium signals in preclinical mouse models of myelin repair

Intracellular Ca2+ signals of oligodendroglia, the myelin-forming cells of the central nervous system, regulate vital cellular processes including myelination. However, studies on oligodendroglia Ca2+ signal dynamics are still scarce, especially during myelin repair, and there are no software solutions to properly analyze the unique Ca2+ signal characteristics in these cells. Here, we provide a comprehensive experimental and analytical workflow to acquire and analyze Ca2+ imaging data of oligodendroglia at the population and single-cell levels in preclinical mouse models of myelin repair. We report diverse ex vivo and in vivo experimental protocols to obtain reproducible Ca2+ imaging data from oligodendroglia in demyelinated lesions. Importantly, we provide an analytical pipeline containing two free, open source and cross-platform software programs, Occam and post-prOccam, that enable the fully automated analysis of one- and two-photon Ca2+ imaging datasets from oligodendroglia obtained by either ex vivo or in vivo Ca2+ imaging techniques. This versatile and accessible experimental and analytical framework, which revealed significant but uncorrelated spontaneous Ca2+ activity in oligodendroglia inside demyelinated lesions, should facilitate the elucidation of Ca2+-mediated mechanisms underlying remyelination and therefore help to accelerate the development of therapeutic strategies for the many myelin-related disorders, such as multiple sclerosis.

neuroscience↗

bioRxiv2022

ExoJ: an ImageJ2/Fiji plugin for automated spatiotemporal detection of exocytosis

Exocytosis is a dynamic physiological process that enables the release of biomolecules to the surrounding environment via the fusion of membrane compartments to the plasma membrane. Understanding its mechanisms is crucial, as defects can compromise essential biological functions. The development of pH-sensitive optical reporters alongside fluorescence microscopy enables the assessment of individual vesicle exocytosis events at the cellular level. Manual annotation represents, however, a time-consuming task, prone to selection biases and human operational errors. Here, we introduce ExoJ, an automated plugin based on ImageJ2/Fiji. ExoJ identifies user-defined genuine populations of exocytic events, recording quantitative features including intensity, apparent size and duration. We designed ExoJ to be fully user-configurable, making it suitable to study distinct forms of vesicle exocytosis regardless of the imaging quality. Our plugin demonstrates its capabilities by showcasing distinct exocytic dynamics among tetraspanins and vesicular SNAREs protein reporters. Assessment of performance on synthetic data demonstrated ExoJ is a robust tool, capable to correctly identify exocytosis events independently of signal-to-noise ratio conditions. We propose ExoJ as a standard solution for future comparative and quantitative studies of exocytosis.

bioinformatics↗

bioRxiv2021

Plasmodium sporozoites require the protein B9 to invade hepatocytes

Plasmodium sporozoites are transmitted to a mammalian host during blood feeding by an infected mosquito and invade hepatocytes for initial replication of the parasite in the liver. This leads to the release of thousands of merozoites into the blood circulation and initiation of the pathogenic blood stages of malaria. Merozoite invasion of erythrocytes has been well characterized at the molecular and structural levels. In sharp contrast, the molecular mechanisms of sporozoite invasion of hepatocytes are poorly characterized. Here we report a new role during sporozoite entry for the B9 protein, a member of the 6-cysteine domain protein family. Using genetic tagging and gene deletion approaches in rodent malaria parasites, we show that B9 is secreted from sporozoite micronemes and is required for productive invasion of hepatocytes. Structural modelling indicates that the N-terminus of B9 forms a beta-propeller domain structurally related to CyRPA, a cysteine-rich protein forming an invasion complex with Rh5 and RIPR in P. falciparum merozoites. We provide evidence that the beta-propeller domain of B9 is essential for protein function during sporozoite entry and interacts with P36 and P52, both also essential for productive invasion of hepatocytes. Our results suggest that, despite using distinct sets of parasite and host entry factors, Plasmodium sporozoites and merozoites may share common structural modules to assemble protein complexes for invasion of host cells.

microbiology↗