Biology subjects

Eichmann, A.

Publications and source records attributed to Eichmann, A..

At least 19 recordsLinked to original sources

bioRxiv2026

The conserved QTQTX motif in the SARS-CoV-2 spike protein is dispensable for cleavage and lung cell entry of the emerging variant BA.3.2

The furin motif in the SARS-CoV-2 spike (S) protein is important for lung cell entry. It is embedded in an extended loop structure and preceded by a highly conserved QTQTX motif that is required for efficient furin cleavage of the SARS-CoV-2 WA-1 S protein. BA.3.2 is an emerging SARS-CoV-2 saltation variant that is spreading globally in April 2026 and encodes for a highly mutated S protein. Here, we analyzed whether the QTQTX motif is also required for spike protein cleavage and lung cell entry of BA.3.2. We report that two patient-derived spike sequences of the BA.3.2 subvariant BA.3.2.2 lack the first QT repeat of the QTQTX motif and show that this motif is largely dispensable for both cleavage and lung cell entry of BA.3.2.2, which we found to depend on TMPRSS2. Our results suggest that the reconfiguration of the BA.3.2 S protein during persistent infection may have significantly altered the determinants of furin cleavage. IMPORTANCEThe furin motif in the SARS-CoV-2 spike (S) protein is unique among sarbecoviruses and constitutes a virulence determinant. A QTQTX motif located immediately upstream of the furin motif is required for furin cleavage of the S protein of the virus that circulated early in the pandemic. Here, we show that the QTQTX motif is largely dispensable for S protein processing and S protein-driven lung cell entry of the emerging saltation variant BA.3.2, which is currently spreading globally. Thus, BA.3.2 evolution within immunocompromised individuals may have relaxed the requirements for furin processing of the spike protein.

microbiology↗

bioRxiv2026

The Nuclear-Cytoskeletal Interface Is a Vulnerability in Aging Endothelium

Vascular aging is a fundamental driver of age-related cardiovascular diseases. Endothelial cells (ECs) lining the vascular lumen of capillaries are specialized, thin cells that supply tissues with metabolites, and their loss in aging poses a threat to tissue perfusion and ischemia risk. Mechanisms causing capillary dropout in aging are largely unknown, although VEGF signaling deficiency is implicated.15 To identify mechanisms involved in vascular aging, we investigated mice with the accelerated aging disorder Progeria, and aged wildtype mice. At the organismal level, Progerin expression reduced sprouting angiogenesis and capillary density in neonatal mouse retinas, which impaired tissue perfusion and increased DNA damage compared to wildtype littermates. Progeric capillaries and aortic ECs displayed a disrupted nuclear-cytoskeletal interface that was shared with aged wildtype mice. 4D EC sprouts derived from Progeria mice had mispositioned nuclei at sprouting tips and bulging nuclei that failed to flatten and obstructed lumen formation, demonstrating cell autonomous defects. Progerin expression in human ECs likewise affected nuclear positioning and flattening and prevented sprouting and lumen formation. Mechanistically, Progerin expression altered LINC complex protein abundance resulting in a failed connection with cytoskeletal Actin and the intermediate filament protein Vimentin. Impairment of the nuclear-cytoskeletal interface was conserved in Progeria patient derived ECs, and partially rescued by inhibiting Progerin with the drug, Progerinin. Taken together, our results reveal that nuclear positioning and flattening is required for angiogenic sprouting and lumen formation respectively and identify the nuclear-cytoskeletal interface as a vulnerability for age-related microvascular dropout and a target for therapeutic intervention.

cell biology↗

bioRxiv2026

RIG-I RNA agonist activates immunostimulatory macrophages to enhance checkpoint immunotherapy for glioblastoma

Glioblastoma (GBM), the most frequent and aggressive primary brain tumor, remains refractory to all current therapies including surgical resection, chemotherapy, radiotherapy and immunotherapy. Immunosuppressive mechanisms in the GBM tumor microenvironment contribute to the lack of anti-tumor adaptive immunity. We found that a subset of tumor associated macrophages (TAMs) can be repolarized into an anti-tumor phenotype via agonist stimulation of the retinoic acid-inducible gene I (RIGI), a cytosolic double-stranded RNA pattern recognition receptor (PRR). In silico analysis of adult GBM datasets available in the public domain revealed that RIGI expression by a subset of activated TAMs positively correlated with patient survival. Studies in syngeneic mouse models of GBM showed that intratumoral delivery of stem-loop RNA 14 (SLR14), a RIG-I agonist, improved the efficacy of chemotherapy, radiotherapy and immunotherapy treatments, beyond the effects of other nuclei acid sensor agonists. We found that RIGI+ macrophages are the main drivers of SLR14 effect, combining activation of TAMs and priming of functional cytotoxic CD8+ T lymphocytes and NK cells. The anti-GBM effect of SLR14 is opening a significant new avenue for adult GBM treatment.

cancer biology↗

bioRxiv2025

Restoring compromised Blood-Retina-Barrier integrity with Netrin-1 overexpression

The blood-retina barrier (BRB) protects retinal neuronal function and enables vision. A compromised, leaky BRB is a hallmark of vision-threatening retinal diseases such as diabetic retinopathy (DR) and wet age-related macular degeneration (AMD) that affect millions of persons worldwide. Strategies to enhance BRB integrity hold promise as therapeutic interventions to prevent vision loss. Previous studies identified Netrin-1 (NTN1) as a key regulator of BRB stability and revealed reduced Netrin-1 signaling in DR patients, suggesting that Netrin-1 supplementation could help preserve BRB function and prevent disease progression. Herein, we used genetic NTN1 overexpression to investigate effects on BRB development and maintenance. We show that global NTN1 overexpression converted leaky vessels at the P5 angiogenic front into a non-leaky state. In pathological settings, NTN1 overexpression reinforced BRB integrity in oxygen- induced retinopathy (OIR), improving electroretinogram (ERG) amplitudes and rescued vascular leak in laser-induced choroidal neovascularization (CNV). Mechanistically, we determined that NTN1 overexpression minimally and transiently affected retinal angiogenesis in an Unc5b independent manner, while Netrins barrier stabilizing effects were Unc5b dependent. These findings establish Netrin-1 as a promising therapeutic target for preventing BRB breakdown in retinal vascular diseases and suggest that reinforcing the Netrin-1/Unc5b signaling pathway may provide a strategy to selectively stabilize the BRB.

molecular biology↗

bioRxiv2025

Divergent endothelial mechanisms drive arteriovenous malformations in Alk1 and Smad4 loss-of-function

BackgroundHereditary hemorrhagic telangiectasia is a genetic disorder caused by loss-of-function mutations in components of the bone morphogenetic protein signaling pathway, leading to arteriovenous malformations. Most prior work has treated BMP-component mutations as mechanistically interchangeable, yet whether distinct genes converge on a shared mechanism remains unclear. We aimed to understand the molecular relationship between BMP signaling and endothelial flow response that leads to AVM formation. MethodsWe expose human endothelial monolayers treated with siRNA against SMAD4 or ALK1 to laminar flow and analyze flow-responsive transcriptomics, flow-responsive BMP signaling activation dynamics, cell polarity and morphology. We analyze the cell-autonomous and non-cell-autonomous migration dynamics of ECs treated with siSMAD4 or siALK1. Using the postnatal mouse retina model, we study EC distribution changes over time in mosaic settings, and assess the remodelling capabilities of Smad4iECKO or Alk1iECKO, relative to littermate controls. ResultsThis study shows that mutations in SMAD4 or ALK1 lead to fundamentally distinct mechanisms of malformation formation. SMAD4 deficiency enhances endothelial responses to blood flow, including transcriptional activation and migration against flow, causing excessive capillary pruning and the development of single large shunts. In contrast, ALK1 deficiency disrupts flow sensing, impairs cell polarization and migration, and promotes a persistent angiogenic state, resulting in dense, hypervascularized networks. RNA sequencing reveals that these transcriptional changes precede flow onset, suggesting early defects in endothelial fate specification. Mosaic in vitro models show that mutant cells co-opt neighboring wild-type cells, while in vivo tracking confirms mutation-specific migration behavior. ConclusionsThese findings reveal divergent cellular programs driving arteriovenous malformations and underscore the need for gene-specific diagnostic and therapeutic strategies. Clinical PerspectiveO_ST_ABSWhat is New?C_ST_ABSO_LIThis study identifies gene-specific mechanisms of AVM formation in endothelial cells with SMAD4 or ALK1 loss-of-function, two major mutations underlying Hereditary Hemorrhagic Telangiectasia. C_LIO_LIUsing multiple side-by-side analyses, the study reveals that SMAD4 deficiency enhances flow-mediated remodeling, while ALK1 deficiency impairs flow sensing and promotes angiogenic persistence. C_LIO_LIRNA sequencing showed that several transcriptional differences precede the onset of flow, indicating early divergence in endothelial cell fate specification and mechanosensory behavior. C_LIO_LIMosaic culture and retinal models demonstrate that mutant cells exert distinct non-cell-autonomous effects on wild-type endothelial cells. C_LI What Are the Clinical Implications?O_LIThis work challenges the prevailing assumption of a unified pathogenic pathway in HHT and supports a model of mutation-specific AVM pathogenesis, with distinct cellular and molecular drivers. C_LIO_LIThe findings provide a mechanistic basis for the variable clinical presentation seen in patients with different HHT mutations. C_LIO_LIIdentification of early transcriptional signatures, such as persistent ANGPT2 or DPP4 upregulation, may offer new biomarkers or therapeutic targets for early intervention before AVMs become clinically symptomatic. C_LIO_LIPersonalized therapeutic strategies could reduce reliance on invasive treatments and shift toward mechanism-based, precision medicine approaches in HHT and related vascular disorders. C_LI

developmental biology↗

bioRxiv2024

Cerebral Venous Blood Flow Regulates Brain Fluid Clearance via Dural Lymphatics

The vascular system regulates brain clearance through arterial blood flow and lymphatic drainage of cerebrospinal fluid (CSF). Idiopathic intracranial hypertension (IIH), characterized by elevated intracranial pressure and dural venous sinus stenoses, can be treated by restoring venous blood flow via venous stenting, suggesting a role for venous blood flow in brain fluid clearance. Using magnetic resonance imaging (MRI) in IIH patients and healthy controls, we identified that dural venous stenoses in IIH were associated with impaired lymphatic drainage, perivenous fluid retention, and brain fluid accumulation. To investigate this further, we developed a mouse model with bilateral jugular vein ligation (JVL), which recapitulated key human findings, including intracranial hypertension, calvarial lymphatic regression, and brain swelling due to impaired clearance. To further dissect the respective roles of dural lymphatics and venous blood flow in brain clearance, we performed JVL in mice with dural lymphatic depletion. These mice exhibited spontaneous elevated intracranial pressure, but JVL did not further exacerbate this effect. Moreover, the synchronous restoration of brain clearance and dural lymphatics observed in mice after JVL was absent in lymphatic-deficient mice.Transcriptomic analyses revealed that lymphatic remodeling induced by JVL was driven by VEGF-C signaling between dural mesenchymal and lymphatic endothelial cells. These findings establish the dural venous sinuses as a critical platform where venous blood flow interacts with mesenchymal cells to preserve dural lymphatic integrity and function, essential for brain fluid clearance.

neuroscience↗

bioRxiv2024

PIEZO1 overexpression in hereditary hemorrhagic telangiectasia arteriovenous malformations

BackgroundHereditary hemorrhagic telangiectasia (HHT) is an inherited vascular disorder characterized by arteriovenous malformations (AVMs). Loss-of-function mutations in Activin receptor-like kinase 1 (ALK1) cause type 2 HHT and Alk1 knockout (KO) mice develop AVMs due to overactivation of VEGFR2/PI3K/AKT signaling pathways. However, the full spectrum of signaling alterations in Alk1 mutants remains unknown and means to combat AVM formation in patients are yet to be developed. MethodsSingle-cell RNA sequencing of endothelial-specific Alk1 KO mouse retinas and controls identified a cluster of endothelial cells (ECs) that was unique to Alk1 mutants and that overexpressed fluid shear stress (FSS) signaling signatures including upregulation of the mechanosensitive ion channel PIEZO1. PIEZO1 overexpression was confirmed in human HHT lesions, and genetic and pharmacological PIEZO1 inhibition was tested in Alk1 KO mice, as well as downstream PIEZO1 signaling. ResultsPharmacological PIEZO1 inhibition, and genetic Piezo1 deletion in Alk1-deficient mice effectively mitigated AVM formation. Furthermore, we identified that elevated VEGFR2/AKT, ERK5-p62-KLF4, hypoxia and proliferation signaling were significantly reduced in Alk1-Piezo1 double ECKO mice. ConclusionsPIEZO1 overexpression and signaling is integral to HHT2, and PIEZO1 blockade reduces AVM formation and alleviates cellular and molecular hallmarks of ALK1-deficient cells. This finding provides new insights into the mechanistic underpinnings of ALK1-related vascular diseases and identifies potential therapeutic targets to prevent AVMs.

molecular biology↗

bioRxiv2024

Shroom3-Rock interaction and profibrotic function: Resolving mechanism of an intronic CKD risk allele.

Common intronic enhancer SNPs in Shroom3 associate with CKD in GWAS, although there is paucity of detailed mechanism. Previously, we reported a role for Shroom3 in mediating crosstalk between TGF{beta}1- & Wnt/Ctnnb1 pathways promoting renal fibrosis (TIF). However, beneficial roles for Shroom3 in proteinuria have also been reported suggesting pleiotropic effects. Here we focused on identifying the specific profibrotic Shroom3 motif. Given known therapeutic roles for Rho-kinase inhibitors in experimental CKD, and the established interaction between Shroom3 and Rock via its ASD2 domain, we hypothesized that Shroom3-mediated ROCK activation played a crucial role in its profibrotic function in high expressors. To test this hypothesis, we developed transgenic mice and cell lines that inducibly overexpressed wild-type- (WT-Sh3) or ASD2-domain deletion- Shroom3 (ASD2{Delta}-Sh3). Prior scRNAseq data showed that during TIF, Shroom3 and Rock co-expression occurred in injured tubular cells and fibroblasts, highlighting cell-types where this mechanism could be involved. Using HEK293T cells, we first confirmed absent ROCK binding and inhibited TGF{beta}1-signaling with ASD2{Delta}-Sh3-overexpression vs WT-Sh3. In mIMCD cells, ASD2{Delta}-Sh3 overexpression, reduced Rock activation (phospho-MYPT1), pro-fibrotic and pro-inflammatory transcripts vs WT-Sh3. Fibroblast proliferation (3T3) was also reduced with ASD2{Delta}-Sh3. In vivo, we studied ureteric obstruction (UUO) and Aristolochic nephropathy (AAN) as TIF models. In AAN, inducible global-, or Pan-tubular specific-, WTSh3-overexpression showed increased azotemia, and TIF vs ASD2{Delta}-Sh3 mice. WT-Sh3 mice consistently showed significant enrichment of Rho-GTPase, TGF{beta}1- and Wnt/CtnnB1- signaling in kidney transcriptome, paralleling Shroom3-coexpressed genes in tubulo-interstitial transcriptomes from human CKD. In UUO, again WT-Sh3 mice recapitulated increased fibrosis vs ASD2{Delta}-Sh3. Importantly, ASD2{Delta}-Sh3 did not develop albuminuria vs WT-Sh3, while mutating a disparate Fyn-binding Shroom3 motif induced albuminuria in mice, suggesting motif-specific roles for Shroom3 in the kidney. Hence, our data show a critical role for the Rock-binding, ASD2-domain in mediating TIF in milieu of Shroom3 excess, with relevance to human CKD.

systems biology↗

bioRxiv2024

Endothelial Rho kinase controls blood vessel integrity and angiogenesis

BackgroundThe Rho kinases 1 and 2 (ROCK1/2) are serine-threonine specific protein kinases that control actin cytoskeleton dynamics. They are expressed in all cells throughout the body, including cardiomyocytes, smooth muscle cells and endothelial cells, and intimately involved in cardiovascular health and disease. Pharmacological ROCK inhibition is beneficial in mouse models of hypertension, atherosclerosis, and neointimal thickening that display overactivated ROCK. However, the consequences of endothelial ROCK signaling deficiency in vivo remain unknown. To address this issue, we analyzed endothelial cell (EC) specific ROCK1 and 2 deletions. MethodsWe generated Cdh5-CreERT2 driven, tamoxifen inducible loss of function alleles of ROCK1 and ROCK2 and analyzed mouse survival and vascular defects through cellular, biochemical, and molecular biology approaches. ResultsWe observed that postnatal or adult loss of endothelial ROCK1 and 2 was lethal within a week. Mice succumbed to multi-organ hemorrhage that occurred because of loss of vascular integrity. ECs displayed deficient cytoskeletal actin polymerization that prevented focal adhesion formation and disrupted junctional integrity. Retinal sprouting angiogenesis was also perturbed, as sprouting vessels exhibited lack of polymerized actin and defective lumen formation. In a three-dimensional endothelial sprouting assay, combined knockdown of ROCK1/2 or knockdown or ROCK2 but not ROCK1 led to reduced sprouting, lumenization and cell polarization defects caused by defective actin and altered VE-cadherin dynamics. The isoform specific role of endothelial ROCK2 correlated with ROCK2 substrate specificity for FAK and LIMK. By analyzing single and three allele mutants we show that one intact allele of ROCK2 is sufficient to maintain vascular integrity in vivo. ConclusionEndothelial ROCK1 and 2 maintain junctional integrity and ensure proper angiogenesis and lumen formation. The presence of one allele of ROCK2 is sufficient to maintain vascular growth and integrity. These data indicate the need of careful consideration for the use of ROCK inhibitors in disease settings.

developmental biology↗

bioRxiv2024

Plasminogen Activator Inhibitor-1 is internalized by endothelial cells via macropinocytosis to evade degradation

Plasminogen activator inhibitor1 (PAI1) promotes hemostasis and is a biomarker of cardiovascular disease but accumulating evidence supports a role for PAI1 in intracellular biology. Recently, we found that PAI1 directly inhibits endothelial nitric oxide synthase (eNOS) and that exogenous PAI1 is internalized and traffics to eNOS. However, prior work has demonstrated that when PAI1 is internalized via LRP1 and uPAR on the cell surface and is internalized and degraded. Our objective was to identify the mechanism by which PAI1 is internalized and evades degradation. Here, we show that PAI1 is internalized by endothelial cells in an energy-dependent manner and persists in the cell for at least 6 hours. Entry is independent of LRP1, uPAR, or clathrin-mediated endocytosis. It is internalized in large vesicles, is inhibited by amiloride and nocodazole, and is partially dependent on CDC42, consistent with macropinocytosis. We propose that following internalization by macropinocytosis, PAI1 evades degradation, permitting eNOS inhibition.

cell biology↗

bioRxiv2023

VEGF-C promotes brain-derived fluid drainage, confers neuroprotection, and improves stroke outcomes

Meningeal lymphatic vessels promote tissue clearance and immune surveillance in the central nervous system (CNS). Vascular endothelium growth factor-C (VEGF-C) is essential for meningeal lymphatic development and maintenance and has therapeutic potential for treating neurological disorders, including ischemic stroke. We have investigated the effects of VEGF-C overexpression on brain fluid drainage, single cell transcriptome in the brain, and stroke outcomes in adult mice. Intra-cerebrospinal fluid administration of an adeno-associated virus expressing VEGF-C (AAV-VEGF-C) increases the CNS lymphatic network. Post-contrast T1 mapping of the head and neck showed that deep cervical lymph node size and drainage of CNS-derived fluids were increased. Single nuclei RNA sequencing revealed a neuro-supportive role of VEGF-C via upregulation of calcium and brain-derived neurotrophic factor (BDNF) signaling pathways in brain cells. In a mouse model of ischemic stroke, AAV-VEGF-C pretreatment reduced stroke injury and ameliorated motor performances in the subacute stage. AAV-VEGF-C thus promotes CNS-derived fluid and solute drainage, confers neuroprotection, and reduces ischemic stroke damage. Short abstractIntrathecal delivery of VEGF-C increases the lymphatic drainage of brain-derived fluids confers neuroprotection, and improves neurological outcomes after ischemic stroke.

neuroscience↗

bioRxiv2023

EphrinA4/EphA4 controls blood pressure via arterial sympathetic innervation

The autonomic sympathetic nervous system innervates peripheral resistance arteries, thereby controlling arterial diameter and modulating blood supply to organs and arterial tone. Despite its fundamental role in blood flow regulation and adaptive response of the cardiovascular system to challenging situations, how sympathetic arterial innervation develops remains poorly understood. We here show that sympathetic arterial innervation is regulated by the axonal guidance molecule EphrinA4 in arterial Smooth Muscle Cells (SMCs), which repels sympathetic axons via the EphA4 receptor. Specific inactivation of EphA4 in sympathetic axons induced a loss of repulsion and increased sympathetic innervation of peripheral arteries throughout life. Functional consequences were a significant increase in arterial tone (resistivity and vasoconstriction), leading to an elevated systemic arterial blood pressure that reached to hypertension under stressful circumstances. These findings identify a novel pathway that negatively regulates sympathetic arterial innervation, and could participate to the appearance of idiopathic resistant hypertension.

physiology↗

bioRxiv2023

Netrin-1 binding to Unc5B regulates Blood-Retina Barrier integrity

BackgroundThe blood brain barrier (BBB) preserves neuronal function in the central nervous system (CNS) by tightly controlling metabolite exchanges with the blood. In the eye, the retina is likewise protected by the blood-retina barrier (BRB) to maintain phototransduction. We showed that the secreted guidance cue Netrin-1 regulated BBB integrity, by binding to endothelial Unc5B and regulating canonical {beta}-catenin dependent expression of BBB gene expression ObjectiveHere, we investigated if Netrin-1-binding to endothelial Unc5B also controlled BRB integrity, and if this process involved Norrin/{beta}-catenin signaling, which is the major known driver of BRB development and maintenance. MethodsWe analyzed Tamoxifen-inducible loss- and gain-of-function alleles of Unc5B, Ntn1 and Ctnnb1 in conjunction with tracer injections and biochemical signaling studies. ResultsInducible endothelial Unc5B deletion, and inducible global Ntn1 deletion in postnatal mice reduced phosphorylation of the Norrin receptor LRP5, leading to reduced {beta}-catenin and LEF1 expression, conversion of retina endothelial cells from a barrier-competent Claudin-5+/PLVAP-state to a Claudin-5-/PLVAP+ leaky phenotype, and extravasation of injected low molecular weight tracers. Inducible Ctnnb1 gain of function rescued vascular leak in Unc5B mutants, and Ntn1 overexpression induced BRB tightening. Unc5B expression in pericytes contributed to BRB permeability, via regulation of endothelial Unc5B. Mechanistically, Netrin-1-Unc5B signaling promoted {beta}-catenin dependent BRB signaling by enhancing phosphorylation of the Norrin receptor LRP5 via the Discs large homologue 1 (Dlg1) intracellular scaffolding protein. ConclusionsThe data identify Netrin1-Unc5B as novel regulators of BRB integrity, with implications for diseases associated with BRB disruption.

cell biology↗

bioRxiv2022

Connexin 43-mediated Neurovascular Interactions Regulate Neurogenesis in the Adult Brain Subventricular Zone

The subventricular zone (SVZ) is the largest neural stem cell (NSC) niche in the adult brain; herein, the blood-brain barrier is leaky, allowing direct interactions between NSCs and endothelial cells (ECs). Mechanisms by which direct NSC-EC interactions in the SVZ control NSC behavior are unclear. We found Cx43 to be highly expressed by both NSCs and ECs in the SVZ, and its deletion in either cell type leads to increased NSC proliferation and neuroblast generation, suggesting that Cx43-mediated NSC-EC interactions maintain NSC quiescence. This is further supported by in vitro studies showing co-culture with ECs decreases NSC proliferation and increases their expression of genes associated with quiescence in a Cx43-dependent manner. Cx43 mediates these effects in a channel-independent manner involving its cytoplasmic tail and ERK activation. Such insights further advance our understanding of NSC regulation in vivo and may inform NSC maintenance ex vivo for stem cell therapies for neurodegenerative disorders.

neuroscience↗

bioRxiv2022

3D-imaging reveals conserved cerebrospinal fluid drainage via meningeal lymphatic vasculature in mice and humans

Meningeal lymphatic vessels (MLVs) contribute to waste product elimination and immune surveillance in brain tissues. MLVs were identified in the dorsal and caudo-basal regions of the dura mater, where they ensure the clearance of cerebrospinal fluid (CSF). Whether MLVs exist in the complex anterior part of the murine and human skull, and how they connect with the glymphatic system and extracranial lymphatic vasculature remained unclear. Here, we generated three-dimensional (3D) maps of MLV drainage by light-sheet fluorescence microscopy (LSFM) imaging of mouse whole-head preparations following fluorescent OVA-A555 tracer injections into the CSF. In humans, we performed real-time magnetic resonance vessel wall imaging (MR-VWI) after systemic gadobutrol injections. We observed a conserved 3D-anatomy of MLVs in mice and humans, and we discovered an extended anterior network around the dural cavernous sinus including multiple capillary beds and exit routes through the foramina of emissary veins. MR-VWI may provide a diagnostic tool for patients with CSF drainage defects and neurological diseases. Short abstractWe established the 3D-anatomy of meningeal lymphatic vasculature and associated CSF drainage by postmortem light-sheet imaging in mice and by real-time magnetic resonance imaging in humans, demonstrating conserved lymphatic circuitries in contact with dural venous sinuses.

neuroscience↗

bioRxiv2021

Competition for endothelial cell polarity drives vascular morphogenesis

Blood vessel formation generates unique vascular patterns in each individual. The principles governing the apparent stochasticity of this process remain to be elucidated. Using mathematical methods, we find that the transition between two fundamental vascular morphogenetic programs - sprouting angiogenesis and vascular remodeling - is established by a shift on collective front-rear polarity of endothelial cells. We demonstrate that the competition between biochemical (VEGFA) and mechanical (blood flow-induced shear stress) cues controls this collective polarity shift. Shear stress increases tension at focal adhesions overriding VEGFA-driven collective polarization, which relies on tension at adherens junctions. We propose that vascular morphogenetic cues compete to regulate individual cell polarity and migration through tension shifts that translates into tissue-level emergent behaviors, ultimately leading to uniquely organized vascular patterns.

developmental biology↗

bioRxiv2021

Endothelial Unc5B controls blood-brain barrier integrity

Blood-brain barrier (BBB) integrity is critical for proper function of the central nervous system (CNS). Here, we showed that the endothelial Netrin1 receptor Unc5B controls BBB integrity by maintaining Wnt/{beta}-catenin signaling. Inducible endothelial-specific deletion of Unc5B in adult mice led to region and size-selective BBB opening. Loss of Unc5B decreased BBB Wnt/{beta}-catenin signaling, and {beta}-catenin overexpression rescued Unc5B mutant BBB defects. Mechanistically, Netrin1 enhanced Unc5B interaction with the Wnt co-receptor LRP6, induced its phosphorylation and activated Wnt/{beta}-catenin downstream signaling. Intravenous delivery of antibodies blocking Netrin1 binding to Unc5B caused a transient disruption of Wnt signaling and BBB breakdown, followed by neurovascular barrier resealing. These data identify Netrin-Unc5B signaling as a novel regulator of BBB integrity with potential therapeutic utility for CNS diseases.

cell biology↗

bioRxiv2021

Defective flow-migration coupling causes arteriovenous malformations in hereditary hemorrhagic telangiectasia

BackgroundActivin receptor-like kinase 1 (ACVRL1, hereafter ALK1) is an endothelial transmembrane serine threonine kinase receptor for BMP family ligands that plays a critical role in cardiovascular development and pathology. Loss-of-function mutations in the ALK1 gene cause type 2 hereditary hemorrhagic telangiectasia (HHT), a devastating disorder that leads to arteriovenous malformations (AVMs). Here we show that ALK1 controls endothelial cell polarization against the direction of blood flow and flow-induced endothelial migration from veins through capillaries into arterioles. MethodsUsing Cre lines that recombine in different subsets of arterial, capillary-venous or endothelial tip cells, we showed that capillary-venous Alk1 deletion was sufficient to induce AVM formation in the postnatal retina. ResultsALK1 deletion impaired capillary-venous endothelial cell polarization against the direction of blood flow in vivo and in vitro. Mechanistically, ALK1 deficient cells exhibited increased integrin signaling interaction with VEGFR2, which enhanced downstream YAP/TAZ nuclear translocation. Pharmacological inhibition of integrin or YAP/TAZ signaling rescued flow migration coupling and prevented vascular malformations in Alk1 deficient mice. ConclusionsOur study reveals ALK1 as an essential driver of flow-induced endothelial cell migration and identifies loss of flow-migration coupling as a driver of AVM formation in HHT disease. Integrin-YAP/TAZ signaling blockers are new potential targets to prevent vascular malformations in HHT patients.

cell biology↗