Biology subjects

Halabi, C. M.

Publications and source records attributed to Halabi, C. M..

5 recordsLinked to original sources

bioRxiv2026

Synaptopodin enables directional mechanoadaptation of integrin-based adhesions

The attachment of cells to their substrate through adhesion complexes is fundamental to tissue architecture and function. These adhesions are inherently optimized to resist shear forces parallel to the substrate, yet certain specialized cells must also withstand substantial perpendicular forces. How cells adapt their adhesion machinery to resist forces in different directions has remained unclear. In the kidney, podocytes experience perpendicular forces from pressurized filtrate flow while maintaining attachment to the glomerular basement membrane through integrin-based adhesions. Here we show that synaptopodin converts adhesions from shear-resistant to perpendicular force-resistant structures through coordinated reorganization of the actin cytoskeleton and adhesion complexes. Using an inertial force application system, we demonstrate that synaptopodin triggers force-dependent redistribution of {beta}1-integrin to the cell periphery specifically in response to perpendicular loading, while synaptopodin-deficient cells lack this directional adaptation and detach. This mechanism operates in multiple cell types and is physiologically essential: synaptopodin-null mice subjected to elevated glomerular pressure develop significant proteinuria and podocyte foot process effacement. These findings reveal a molecular basis for directional mechanoadaptation, whereby a single protein enables cells to reconfigure their adhesion architecture in response to the direction of applied force.

biophysics↗

bioRxiv2026

Orthogonal Force Balance Between Contractility and Shear Stress Governs Podocyte Dynamics

Maintenance of tissue barriers under mechanical stress represents a fundamental biological challenge across organ systems. In the kidney, podocyte cells withstand highly variable hemodynamic forces while preserving a tensioned, nanostructured filtration barrier. Dysregulation of this barrier leads to significant pathology, but the mechanical principles underlying homeostasis of cells against flow of filtrates have not yet been identified. Here, we uncover a counterintuitive mechanical homeostasis mechanism whereby podocyte attachment depends on a dynamic balance between external fluid shear stress and internal cellular contractility. Integrated biomechanical modeling and experiment reveal a previously unrecognized mechanosensing circuit that optimizes integrin distribution at foot process peripheries. Our mathematical framework for cell-matrix adhesion stability reveals, surprisingly, that reducing blood pressure can worsen outcomes when cell contractility is impaired, contrary to clinical belief that lowering blood pressure universally benefits cellular adhesion and kidney function. We validated this principle through mouse models with manipulated blood pressure and myosin inhibition, demonstrating that concurrent reduction of both shear stress and contractility worsens podocyte injury and proteinuria. Super-resolution microscopy confirms our predicted integrin redistribution patterns under these mechanical perturbations. These findings establish a fundamental mechanobiological principle applicable beyond nephrology, and suggest potential treatment pathways targeting non-equilibrium steady states.

cell biology↗

bioRxiv2024

Endothelial cell Piezo1 promotes vascular smooth muscle cell differentiation on large arteries

Vascular stabilization is a mechanosensitive process, in part driven by blood flow. Here, we demonstrate the involvement of the mechanosensitive ion channel, Piezo1, in promoting arterial accumulation of vascular smooth muscle cells (vSMCs) during zebrafish development. Using a series of small molecule antagonists or agonists to temporally regulate Piezo1 activity, we identified a role for the Piezo1 channel in regulating klf2a levels and altered targeting of vSMCs between arteries and veins. Increasing Piezo1 activity suppressed klf2a and increased vSMC association with the cardinal vein, while inhibition of Piezo1 activity increased klf2a levels and decreased vSMC association with arteries. We supported the small molecule data with in vivo genetic suppression of piezo1 and 2 in zebrafish, resulting in loss of transgelin+ vSMCs on the dorsal aorta. Further, endothelial cell (EC)-specific Piezo1 knockout in mice was sufficient to decrease vSMC accumulation along the descending dorsal aorta during development, thus phenocopying our zebrafish data, and supporting functional conservation of Piezo1 in mammals. To determine mechanism, we used in vitro modeling assays to demonstrate that differential sensing of pulsatile versus laminar flow forces across endothelial cells changes the expression of mural cell differentiation genes. Together, our findings suggest a crucial role for EC Piezo1 in sensing force within large arteries to mediate mural cell differentiation and stabilization of the arterial vasculature.

developmental biology↗

bioRxiv2023

Electrophysiology of human iPSC-derived vascular smooth muscle cells and cell autonomous consequences of Cantu Syndrome mutations

ObjectiveCantu Syndrome (CS), a multisystem disease with a complex cardiovascular phenotype, is caused by GoF variants in the Kir6.1/SUR2 subunits of ATP-sensitive potassium (KATP) channels, and is characterized by low systemic vascular resistance, as well as tortuous, dilated vessels, and decreased pulse-wave velocity. Thus, CS vascular dysfunction is multifactorial, with distinct hypomyotonic and hyperelastic components. To dissect whether such complexities arise cell-autonomously within vascular smooth muscle cells (VSMCs), or as secondary responses to the pathophysiological milieu, we assessed electrical properties and gene expression in human induced pluripotent stem cell-derived VSMCs (hiPSC-VSMCs), differentiated from control and CS patient-derived hiPSCs, and in native mouse control and CS VSMCs. Approach and ResultsWhole-cell voltage-clamp of isolated aortic and mesenteric VSMCs isolated from wild type (WT) and Kir6.1[V65M] (CS) mice revealed no difference in voltage-gated K+ (Kv) or Ca2+ currents. Kv and Ca2+ currents were also not different between validated hiPSC-VSMCs differentiated from control and CS patient-derived hiPSCs. Pinacidil-sensitive KATP currents in control hiPSC-VSMCs were consistent with those in WT mouse VSMCs, and were considerably larger in CS hiPSC-VSMCs. Consistent with lack of any compensatory modulation of other currents, this resulted in membrane hyperpolarization, explaining the hypomyotonic basis of CS vasculopathy. Increased compliance and dilation in isolated CS mouse aortae, was associated with increased elastin mRNA expression. This was consistent with higher levels of elastin mRNA in CS hiPSC-VSMCs, suggesting that the hyperelastic component of CS vasculopathy is a cell-autonomous consequence of vascular KATP GoF. ConclusionsThe results show that hiPSC-VSMCs reiterate expression of the same major ion currents as primary VSMCs, validating the use of these cells to study vascular disease. The results further indicate that both the hypomyotonic and hyperelastic components of CS vasculopathy are cell-autonomous phenomena driven by KATP overactivity within VSMCs.

physiology↗

bioRxiv2022

Mutation in the matricellular gene fibulin-4 leads to endothelial dysfunction in resistance arteries

Mutations in fibulin-4 (FBLN4), a matricellular gene required for extracellular matrix (ECM) assembly, result in autosomal recessive cutis laxa type 1B (ARCL1B), a syndrome characterized by loose skin, aortic aneurysms, pulmonary emphysema and skeletal abnormalities. Fbln4E57K/E57K mice recapitulated the phenotypes observed in ARCL1B. In particular, they exhibited ascending aortic aneurysms, elastic fiber fragmentation and increased stiffness in large arteries, and systolic hypertension. Surprisingly however, internal elastic laminae of small resistance and muscular arteries were intact. Here, we show that the increased pulsatile flow resulting from the structural abnormalities and increased stiffness of conduit arteries in Fbln4E57K/E57K mice leads to increased shear stress, a highly oxidative environment, and endothelial dysfunction related to reduced nitric oxide bioavailability in resistance mesenteric arteries. These data have significant implications, not only for the basic biology of ECM assembly along the arterial tree, but also for the clinical consequences of large artery stiffness on the microcirculation.

physiology↗