Biology subjects

Devany, J.

Publications and source records attributed to Devany, J..

5 recordsLinked to original sources

bioRxiv2024

Mechanosensitive FHL2 tunes endothelial function

Endothelial tissues are essential mechanosensors in the vasculature and facilitate adaptation to various blood flow-induced mechanical cues. Defects in endothelial mechanoresponses can perturb tissue remodelling and functions leading to cardiovascular disease progression. In this context, the precise mechanisms of endothelial mechanoresponses contributing to normal and diseased tissue functioning remain elusive. Here, we sought to uncover how flow-mediated transcriptional regulation drives endothelial mechanoresponses in healthy and atherosclerotic-prone tissues. Using bulk RNA sequencing, we identify novel mechanosensitive genes in response to healthy unidirectional flow (UF) and athero-prone disturbed flow (DF). We find that the transcription as well as protein expression of Four-and-a-half LIM protein 2 (FHL2) are enriched in athero-prone DF both in vitro and in vivo. We then demonstrate that the exogenous expression of FHL2 is necessary and sufficient to drive discontinuous adherens junction morphology and increased tissue permeability. This athero-prone phenotype requires the force-sensitive binding of FHL2 to actin. In turn, the force-dependent localisation of FHL2 to stress fibres promotes microtubule dynamics to release the RhoGEF, GEF-H1, and activate the Rho-ROCK pathway. Thus, we unravelled a novel mechanochemical feedback wherein force-dependent FHL2 localisation promotes hypercontractility. This misregulated mechanoresponse creates highly permeable tissues, depicting classic hallmarks of atherosclerosis progression. Overall, we highlight crucial functions for the FHL2 force-sensitivity in tuning multi-scale endothelial mechanoresponses.

cell biology↗

bioRxiv2022

Tissue confinement regulates cell growth and size in epithelia

Cell proliferation is a central process in tissue development, homeostasis and disease. Yet how proliferation is regulated in the tissue context remains poorly understood. Here, we introduce a quantitative framework to elucidate how tissue growth dynamics regulate cell proliferation. We show that tissue growth causes confinement that suppresses cell growth; however, this confinement does not directly affect the cell cycle. This leads to uncoupling between rates of cell growth and division in epithelia and, thereby, reduces cell size. Division becomes arrested at a minimal cell size, which is consistent across diverse epithelia in vivo. Here, the nucleus approaches a volume limit set by the compacted genome. The loss of Cyclin D1-dependent cell size regulation results in an abnormally high nuclear-to-cytoplasmic volume ratio and DNA damage. Overall, we demonstrate how epithelial proliferation is regulated by the interplay between tissue confinement and cell size regulation. Highlights- In epithelia, regulation of cell growth and cycle are uncoupled - Cell growth is regulated by tissue-scale dynamics, which determine confinement - Cell volume in epithelial tissue is described by G1 sizer model with a tunable growth rate - Volume of cells in epithelial tissues is near a minimum set by genome size

biophysics↗

bioRxiv2021

Dia1 Coordinates Differentiation and Cell Sorting in a Stratified Epithelium

Although implicated in adhesion, few studies address how actin assembly factors guide cell positioning in multicellular tissue. The formin, Dia1, localizes to the proliferative basal layer of epidermis. In organotypic cultures, Dia1 depletion reduced basal cell density and resulted in stratified tissue with disorganized differentiation and proliferative markers. Since crowding induces differentiation in epidermal tissue, we hypothesized that Dia1 allows cells to reach densities amenable to differentiation prior to stratification. Consistent with this hypothesis, forced crowding of Dia1-deficient cells rescued transcriptional abnormalities. Dia1 promotes rapid growth of lateral adhesions, a behavior consistent with the ability of cells to remain monolayered when crowded. In aggregation assays, cells sorted into distinct layers based on Dia1 expression status. These results suggested that as basal cells proliferate, reintegration and packing of Dia1-positive daughter cells is favored while Dia1-negative cells tend to delaminate to a suprabasal compartment. These data demonstrate how formin expression patterns play a crucial role in constructing distinct domains within stratified epithelia. SummaryHarmon et al demonstrate that differential expression of an actin nucleator, the formin, Dia1, drives cell sorting and maintains distinct morphological domains within an epithelial tissue. This illuminates the possible utility of evolving a large formin family in orchestrating the compartmentalization and differentiation of complex tissues.

cell biology↗

bioRxiv2019

Cell division Rate Controls Cell Shape Remodeling in Epithelia

Epithelia have distinct cellular architectures, which are established in development, re-established after wounding, and maintained during tissue homeostasis despite cell turnover and mechanical perturbations. In turn, cell shape also controls tissue function as a regulator of cell differentiation, proliferation, and motility. Here we investigate cell shape changes in a model epithelial monolayer. After the onset of confluence, cells continue to proliferate and change shape over time, eventually leading to a final architecture characterized by arrested motion and more regular cell shapes. Such monolayer remodeling is robust, with qualitatively similar evolution in cell shape and dynamics observed across disparate perturbations. Here we quantify differences in monolayer remodeling guided by the active vertex model to identify underlying order parameters controlling epithelial architecture. When monolayers are formed atop extracellular matrix with varied stiffness, we find the cell density at which motion arrests varies significantly but the cell shape remains constant, consistent with the onset of tissue rigidity. In contrast, pharmacological perturbations can significantly alter the cell shape at which tissue dynamics is arrested, consistent with varied amounts of active stress within the tissue. Across all experimental conditions the final cell shape is well correlated to the cell proliferation rate, and cell cycle inhibition immediately arrests cell motility. Finally, we demonstrate cell-cycle variation in junctional tension as a source of active stress within the monolayer. Thus, the architecture and mechanics of epithelial tissue can arise from an interplay between cell mechanics and stresses arising from cell cycle dynamics. SIGNIFICANCE STATEMENTThe morphology of biological tissue is determined by the shape and density of constituent cells. Here we measure the dynamics of cells in model epithelial tissues to study the evolution of their shape and density over time. Guided by a mathematical model, we find that cell shape is controlled by rigidity and active stresses within the tissue. We then show that cell cycle dynamics are the source of active stress that drives epithelial remodeling.

biophysics↗

bioRxiv2019

A DNA-based voltmeter for organelles

The role of membrane potential in most intracellular organelles remains unexplored because of the lack of suitable probes. We describe a DNA-based fluorescent reporter that quantitates membrane potential and can be targeted to specific organelles in live cells. It is equipped with a voltage sensitive fluorophore, a reference fluorophore for ratiometric quantification, and acts as an endocytic tracer. We could thereby measure the membrane potential of different intracellular organelles in living cells, which has not been possible previously. Our understanding of how membrane potential regulates organelle biology is poised to expand through the use of these new sensors.\n\nOne Sentence SummaryUsing a DNA-based voltmeter we can non-invasively measure the membrane potential of specific organelles in live cells.

biophysics↗