Biology subjects

Hirashima, T.

Publications and source records attributed to Hirashima, T..

15 recordsLinked to original sources

bioRxiv2026

Geometric coordination of endothelial invasion and vascular patterning during epithelial morphogenesis

As organs grow and remodel in three dimensions, developing vascular networks extend through the tissue while maintaining spatial coordination and establishing connections between distant sprouts. How local endothelial behavior generates vascular patterns within such deforming environments remains poorly understood. Here, using the developing mouse epididymis, we combine two-photon live microscopy, pharmacological perturbations, and mathematical modeling to investigate angiogenesis alongside epithelial tubule folding. Endothelial cells invade the organ interior while maintaining proximity to the deforming tubule. Live imaging reveals dynamic protrusions directed toward the epithelium and a characteristic sequence in which endothelial fronts approach the tubule, stop, and maintain their separation despite continued folding. ERK activity promotes endothelial extension and declines during the transition to distance maintenance. From these observations, we derive a minimal follow-and-stop rule that captures endothelial positioning relative to the changing epithelium. Extending this model to three dimensions reveals how epithelial folding can bring otherwise distant endothelial fronts together, creating opportunities for vascular connection. Explants exhibiting greater three-dimensional folding also show a higher observed frequency of endothelial connections. Our findings support a geometric framework in which local endothelial dynamics and tissue-scale deformation can jointly contribute to vascular patterning during organ morphogenesis.

developmental biology↗

bioRxiv2026

Geometric confinement regulates ERK signaling dynamics and collective migration

Collective cell migration is a fundamental process in morphogenesis, tissue repair, cancer invasion, and frequently occurs under geometric confinement in vivo. However, how confinement interfaces with signaling pathways that coordinate collective motion remains poorly understood. Here, we confine migrating epithelial monolayers within adhesive microstripes of defined width and observe a progressive slow-down of collective migration with increasing spatial confinement. Combining biophysical modeling, live imaging of ERK activity, and pharmacological perturbations, we show that confinement increases tissue crowding while reducing cell and nuclear projected areas, thereby shifting epithelial tissues toward a mechanically compressed state associated with dampened ERK waves. Across conditions, migration speed scales with ERK signaling dynamics, which correlates with EGFR signaling as well as cell and nuclear projected areas, together serving as quantitative proxies for the confinement-imposed mechanical state. Pharmacological inhibition of ROCK restores cell spreading, ERK signaling, and migration under strong confinement, demonstrating that this state is reversible and governed by actomyosin contractility. Together, our results identify geometric confinement as a physical regulator of a contractility-dependent mechanochemical state that controls ERK signaling and collective migration in epithelial tissues.

biophysics↗

bioRxiv2026

Transient contractility attenuation reprograms epithelial cells into a protrusion-driven state that drives tissue fluidization

Collective cell migration drives tissue morphogenesis, repair and remodeling, and is often accompanied by transitions from solid-like to fluid-like states. While such tissue fluidization has been linked to physical parameters such as cell density, shape and activity, how it is actively regulated by mechano-chemical interplay remains unclear. Previous research has shown that transient attenuation of actomyosin contractility induces a transition from pulsatile, spatially confined motion to coherent, persistent long-range collective flow; however, the underlying cellular and signaling mechanisms remain unclear. Here we uncover the mechanistic basis by which transient perturbation of cell contractility reprograms the migration mode of confluent epithelial cells into a protrusion-driven, fluidizing state, by combining kinase-reporter live imaging, force measurements and mathematical modeling. This transition arises from coordinated changes in cell morphology and mechanics, including reduced cortical tension and greater stretch-induced cell strain, together with enhanced cell-substrate adhesion and force transmission. At the signaling level, this process is accompanied by a rewiring of extracellular signal-regulated kinase (ERK)-mediated mechanotransduction toward a protrusion-coupled mode that sustains migration even under fully confluent conditions. Consistently, a multicellular computational model further demonstrates that protrusion-driven migration is sufficient to promote shape-velocity alignment and drive a transition from caged to flocking-like collective states. Together, our results identify transient contractility attenuation followed by recovery as a trigger for a protrusion-driven state that fluidizes confluent epithelial tissues through coordinated remodeling of cytoskeletal, adhesive, and signaling systems.

synthetic biology↗

bioRxiv2026

Flow-driven lumen remodeling and valve opening in the vas deferens

Biological ducts must transport fluids while preserving structural integrity, yet how mechano-signaling coordinates wall deformation with luminal flow in vivo remains unclear. Here we combine intravital two-photon excitation microscopy, light-sheet imaging and FRET-based kinase biosensors to resolve ejaculation-like events in the mouse vas deferens. Acute phenylephrine stimulation elicits a sequence of luminal dynamics: an initial retrograde pressure-redistribution wave followed by a ballistic antegrade flow that propels dense sperm suspensions from proximal to distal duct. This contraction-driven flow opens a normally collapsed, wrinkled distal segment, driving progressive lumen expansion and unfolding of epithelial wrinkles. We show that the vas deferens actively modulates luminal geometry in response to these flow dynamics: ROCK activity in smooth muscle is required for global contraction and cAMP-associated signaling modulates this contractile response. By contrast, ERK activity in circumferential smooth muscle is dispensable for the ductal contraction but essential for active, flow-dependent remodeling of the distal lumen, forming the core of the mechano-signaling module that couples sperm flow to valve opening. These findings establish the vas deferens as an experimentally tractable model of ductal tissue hydraulics and reveal a mechano-signaling framework by which a tubular organ converts transient muscular input into robust, directional luminal transport. SIGNIFICANCE STATEMENTMale reproductive ducts must rapidly propel sperm-containing fluids forward, yet how they do so in living animals has remained unclear due to a lack of imaging studies. By combining real-time in vivo imaging and molecular activity reporters, we observe the mouse vas deferens at work and link each phase of ejaculation-like transport to specific signaling pathways. We find that ROCK activity is closely linked to the overall squeeze of the duct, cAMP-associated signaling modulates this contractile response, and ERK is uniquely required to open and remodel a normally closed distal valve in response to flow. This mechano-signaling framework offers a general blueprint for how tubular organs coordinate muscle contraction, tissue shape change, and directional luminal transport.

physiology↗

bioRxiv2024

Compositional Flexibility of the ER-Mitochondria Encounter Structure

Yeast mitochondria receive the majority of their lipids from the endoplasmic reticulum (ER) via the heterotetrameric ERMES lipid transport complex. This complex is thought to establish a lipid transporting tube of fixed composition spanning the space between both organelles. Intriguingly, however, some of the lipid-transporting components of the complex can be replaced by an artificial ER-mitochondria tether without lipid transport activity, indicating that ERMES subunits are not all of equal importance for lipid transport. Here, we propose a model whereby lipid transfer by the ERMES complex can occur with various sub-ensembles of ERMES, and minimally with only one of the four members, namely Mmm1. Our results imply flexibility in the composition of the ERMES complex, which might help it accommodate various interorganelle distances.

cell biology↗

bioRxiv2023

E-cadherin-dependent phosphorylation of EGFR governs a homeostatic feedback loop controlling intercellular junction viscosity and collective migration modes.

Actomyosin tension has been shown to be a ubiquitous driver of tissue morphogenesis1, 2. The Rho pathway, a prominent regulatory network influencing cortical tension, plays a central role in both tissue reorganisation and cell migration3-6. While viscous dissipation in the actin network is commonly regarded as a constant passive parameter in cell migration in both 2D and 3D contexts, there is limited knowledge concerning the regulation of dissipative forces arising from viscous drag between cells during collective rearrangement. Here, we found that the phosphorylation of Epithelial Growth Factor Receptor (EGFR) downstream of de novo E-cadherin adhesion7, 8 orchestrates a feedback loop, thereby governing intercellular viscosity via the Rac pathway regulating actin dynamics. Our findings highlight how the E-cadherin-dependent EGFR activity controls the migration mode of collective cell movements independently of intercellular tension. Combining molecular cell biology, micropatterning, and in silico simulation, our work suggests the existence of a regulatory loop by which cells can tune junctional actin viscosity, with implications for the phenomenology of morphogenetic movements.

cell biology↗

bioRxiv2023

Interplay between mechanochemical patterning and glassy dynamics in cellular monolayers

Living tissues are characterized by an intrinsically mechano-chemical interplay of active physical forces and complex biochemical signalling pathways. Either feature alone can give rise to complex emergent phenomena, for example mechanically driven glassy dynamics and rigidity transitions, or chemically driven reaction-diffusion instabilities. An important question is how to quantitatively assess the contribution of these different cues to the large-scale dynamics of biological materials. We address this in MDCK monolayers, considering both mechanochemical feedbacks between ERK signalling activity and cellular density as well as a mechanically active tissue rheology via a self-propelled vertex model. We show that the relative strength of active migration forces to mechanochemical couplings controls a transition from uniform active glass to periodic spatiotemporal waves. We parameterize the model from published experimental datasets on MDCK monolayers, and use it to make new predictions on the correlation functions of cellular dynamics and the dynamics of topological defects associated with the oscillatory phase of cells. Interestingly, MDCK monolayers are best described by an intermediary parameter region in which both mechanochemical couplings and noisy active propulsion have a strong influence on the dynamics. Finally, we study how tissue rheology and ERK waves feedback on one another, and uncover a mechanism via which tissue fluidity can be controlled by mechano-chemical waves both at the local and global levels.

biophysics↗

bioRxiv2022

Three-dimensional analysis and in vivo imaging for sperm release and transport in the murine seminiferous tubule

IntroductionSpermatozoa released from Sertoli cells must be transported to the epididymis. However, the contribution of the peristaltic motion in the seminiferous tubule to sperm release and transport remains unclear. We, therefore, investigated luminal flow and movements in the seminiferous tubules by three-dimensional analysis and in vivo imaging. Materials and MethodsSerial testicular sections were cut in 5-m-thick and 50-m-interval and stained by PAS-hematoxylin. After the three-dimensional reconstruction of the seminiferous tubules, the localization of the flowing spermatozoa and stages observed in the sections were recorded in each reconstructed tubule. The luminal movements in the seminiferous tubule were observed by in vivo imaging using a fluorescent-reporter mouse and two-photon excitation microscopy system. ResultsFlowing spermatozoa were mainly scattered in the lumina at stage VII/VIII, and clustered spermatozoa were also found in some regions. The clustered spermatozoa were observed at zero to two regions in each seminiferous tubule. Flowing spermatozoa were also found in the opposite direction to the rete testis. The flagellum direction of the spermatozoa attached to the seminiferous epithelium was reversed within a few seconds to a few tens of seconds when observed by in vivo imaging. The epithelium at the inner curve of the seminiferous tubule moved more actively and attached fewer spermatozoa compared to that at the outer curve. DiscussionThis study revealed the presence of repeatedly reversed luminal flow in the seminiferous tubule. Such movements are suggested to help the sperm release from the Sertoli cells and the following aggregation of the released spermatozoa.

cell biology↗

bioRxiv2021

ERK-mediated Curvature Feedback Regulates Branching Morphogenesis in Lung Epithelial Tissue

Intricate branching patterns emerge in internal organs because of the repetitive presence of simple deformations in epithelial tissues. During murine lung development, epithelial cells in distal tips of a single tube require fibroblast growth factor (FGF) signals generated by their surrounding mesenchyme to form repetitive tip bifurcations. However, it remains unknown how the cells employ FGF signaling to convert their behaviors to achieve the recursive branching processes. Here we show a self-sustained epithelial regulatory system during the murine lung branching morphogenesis, mediated by extracellular signal-regulated kinase (ERK), which acts as a downstream driver of FGF signaling. We found that tissue-scale curvature regulated ERK activity in the lung epithelium using two-photon live cell imaging and mechanical perturbations. ERK was activated specifically in epithelial tissues with a positive curvature, regardless of whether the change in curvature was attributable to morphogenesis or artificial perturbations. Moreover, ERK activation accelerated actin polymerization specifically at the apical side of cells, and mechanically contributed to the extension of the apical membrane, leading to a decrease in epithelial tissue curvature. These results indicate the existence of negative feedback loop between tissue curvature and ERK activity beyond scale. We confirmed that this regulation was sufficient to generate the recursive branching processes by a mathematical model. Taken together, we propose that ERK mediates the curvature feedback loop underlying the process of branching morphogenesis in developing lungs.

developmental biology↗

bioRxiv2021

Metastatic Single Tumor Cells Evade NK Cell-mediated Killing by Thrombin-mediated Loss of the Activating Ligand CD155/PVR/Necl-5

Natural killer (NK) cells lyse invading tumor cells to limit metastatic growth in the lung, but how some cancers evade this host protective mechanism to establish a growing lesion is not known. Here we have combined ultra-sensitive bioluminescence whole body imaging with intravital two-photon microscopy involving genetically-encoded biosensors to examine this question. NK cells eliminated disseminated tumor cells from the lung within 24 hrs of arrival, but not thereafter. Intravital dynamic imaging revealed that a disseminated tumor cell in a pulmonary capillary interacts with an NK cell every 2 hrs on average. In the first 4 hrs after tumor cell arrival, 50% of such encounters lead to tumor cell death but after 24 hrs of arrival, nearly 100% of the interactions result in the survival of the tumor cell. This evasion of NK cell surveillance is mediated by thrombin-dependent loss of cell surface CD155/PVR/Necl-5, a ligand for the NK cell activating receptor DNAM-1. This loss prevents the NK cell signaling needed for effective killing of tumor targets. By quantitatively visualizing the evasion of NK cell surveillance, we have uncovered a molecular mechanism for cancer evasion and provided an explanation for the anti-metastatic effect of anticoagulants. SUMMARYIntravital functional two-photon microscopy reveals that metastatic tumor cells lodged in pulmonary capillaries acquire resistance to patrolling NK cells. Protease-mediated loss of the activating ligand CD155/PVR/Necl-5 on tumor cells prevents NK cells from ERK activation and tumor cell killing.

immunology↗

bioRxiv2020

Interplay between medial nuclear stalling and lateral cellular flow underlies cochlear duct morphogenesis

A notable example of spiral architecture in organs is the mammalian cochlear duct, where the duct morphology is critical for hearing function. Molecular genetics has revealed the necessary signaling molecules for the formation of spirals in organs, but it remains unclear how cellular dynamics generate bending and coiling of the cochlear duct during development. Here we show two modes of multicellular dynamics underlying the morphogenetic process by combining deep tissue live-cell imaging, Forster resonance energy transfer (FRET)-based quantitation, and mathematical modeling. First, surgical separation of the cochlear duct revealed that bending forces reside primarily in the medial side of the duct. In the medial pseudostratified epithelium, we found that nuclei stall at the luminal side during interkinetic nuclear migration, which would cause the extension of the luminal side, thereby bending the duct. Second, long-term organ-scale FRET imaging of extracellular signal-regulated kinase (ERK) activity showed that helical ERK activation waves propagate from the duct tip concomitant with the reverse multicellular flow in the lateral side of the duct, resulting in advection-based duct elongation. We propose an interplay of distinct multicellular behaviors underpinning spiral morphogenesis in the developing cochlear duct.

developmental biology↗

bioRxiv2020

Incoherent feedforward regulation via Sox9 and Erk underpins mouse tracheal cartilage development

Tracheal cartilage provides architectural integrity to the respiratory airway, and defects in this structure during embryonic development cause severe congenital anomalies. Previous genetic studies have revealed genes that are critical for the development of tracheal cartilage. However, it is still unclear how crosstalk between these proteins regulates tracheal cartilage formation. Here we show a core regulatory network underlying murine tracheal chondrogenesis from embryonic day (E) 12.5 to E15.5, by combining volumetric imaging of fluorescence reporters, inhibitor assays, and mathematical modeling. We focused on SRY-box transcription factor 9 (Sox9) and extracellular signal-regulated kinase (Erk) in the tracheal mesenchyme, and observed a synchronous, inverted U-shaped temporal change in both Sox9 expression and Erk activity with a peak at E14.5, whereas the expression level of downstream cartilage matrix genes, such as collagen II alpha 1 (Col2a1) and aggrecan (Agc1), monotonically increased. Inhibitor assays revealed that the Erk signaling pathway functions as an inhibitory regulator of tracheal cartilage differentiation during this period. These results suggest that expression of the cartilage matrix genes is controlled by an incoherent feedforward loop via Sox9 and Erk, which is supported by a mathematical model. Furthermore, the modeling analysis suggests that a Sox9-Erk incoherent feedforward regulation augment the robustness against the variation of upstream factors. The present study provides a better understanding of the regulatory network underlying the tracheal development and will be helpful for efficient induction of tracheal organoids.

developmental biology↗

bioRxiv2020

Theory of mechano-chemical patterning and optimal migration in cell monolayers

Collective cell migration offers a rich field of study for non-equilibrium physics and cellular biology, revealing phenomena such as glassy dynamics [1], pattern formation [2] and active turbulence [3]. However, how mechanical and chemical signaling are integrated at the cellular level to give rise to such collective behaviors remains unclear. We address this by focusing on the highly conserved phenomenon of spatio-temporal waves of density [2, 4-8] and ERK/MAPK activation [9-11], which appear both in vitro and in vivo during collective cell migration and wound healing. First, we propose a biophysical theory, backed by mechanical and optogenetic perturbation experiments, showing that patterns can be quantitatively explained by a mechano-chemical coupling between three-dimensional active cellular tensions and the mechano-sensitive ERK/MAPK pathway. Next, we demonstrate how this biophysical mechanism can robustly induce migration in a desired orientation, and we determine a theoretically optimal pattern for inducing efficient collective migration fitting well with experimentally observed dynamics. We thereby provide a bridge between the biophysical origin of spatio-temporal instabilities and the design principles of robust and efficient long-ranged migration.

biophysics↗

bioRxiv2019

ERK-mediated mechanochemical waves direct collective cell polarization

During collective migration of epithelial cells, the migration direction is aligned over a large, tissue-scale expanse. Although the collective cell migration is known to be directed by mechanical forces transmitted via cell-cell junctions, it remains elusive how the intercellular force transmission is coordinated with intracellular biochemical signaling to achieve collective movements. Here we show that intercellular coupling of extracellular signal-regulated kinase (ERK)-mediated mechanochemical feedback in individual cells yields long-distance transmission of guidance cues. Mechanical stretch activates ERK through epidermal growth factor receptor (EGFR) activation, and the ERK activation triggers cell contraction. In addition, the contraction of the activated cell pulls neighboring cells via cell-cell junctions, evoking another round of ERK activation and contraction in the neighbors. Furthermore, anisotropic contraction based on front-rear cell polarization guarantees unidirectional propagation of ERK activation waves, and in turn, the ERK activation waves direct multicellular alignment of the polarity, leading to long-range ordered migration. Our findings reveal that mechanical forces mediate intercellular signaling underlying sustained transmission of guidance cues for collective cell migration.

cell biology↗

bioRxiv2017

Anisotropic Cellular Mechanoresponse for Radial Size Maintenance of Developing Epithelial Tubes

Cellular behaviors responding to mechanical forces control the size of multicellular tissues as demonstrated in isotropic size maintenance of developing tissues. However, how mechanoresponse systems work to maintain anisotropic tissue size including tube radial size remains unknown. Here we reveal the system underlying radial size maintenance of the murine epididymal tubule by combining quantitative imaging, mathematical modeling, and mechanical perturbations. We found that an oriented cell intercalation making the tubule radial size smaller counteracts a cell tension reduction due to neighbor cell division along the tubule circumferential axis. Moreover, we demonstrated that the tubule cells enhance actomyosin constriction driving the cell intercalation in response to mechanical forces anisotropically applied on the cells. Our results suggest that epididymal tubule cells have endogenous systems for responding as active cell movement to mechanical forces exclusively along the circumferential axis, and the anisotropic cellular mechanoresponse spontaneously controls the tubule radial size.

bioinformatics↗