Biology subjects

De Val, S.

Publications and source records attributed to De Val, S..

8 recordsLinked to original sources

bioRxiv2026

Hypoxia differentially affects coronary vessel formation during heart development

BACKGROUNDThe coronary vessel system is a dense and diverse network of arteries, veins and capillaries formed by endothelial cells from a variety of sources. While hypoxia is a known stimulus for angiogenic sprouting generally, the exact mechanisms by which hypoxia, and resultant increased VEGFA, influences vessel growth in the heart are not clearly delineated. METHODSWe used a genetic model to mimic hypoxia through ectopic stabilisation of myocardial HIF. This enabled us to study the consequences of hypoxia without vascular depletion. Changes in coronary ECs in these hearts relative to littermate controls were assessed by single cell RNA-sequencing, and by examining the activity of enhancer:reporter transgenes active in different coronary vessel beds downstream of distinct vascular regulatory pathways. RESULTSAnalysis of hypoxia-mimic hearts found increased angiogenic gene expression alongside expanded activity of the VEGFA-MEF2-driven angiogenic regulatory pathway in a pattern that indicated increased endocardial-derived angiogenic sprouting. Conversely, regulatory pathways specifically active in the sinus venosus (SV)-derived plexus showed little variance in response to stabilized HIF, and sprouting from the SV was not expanded. Although hypoxia and increased VEGFA levels have been previously linked to increased arterial differentiation, we saw little change in initial arterial EC differentiation in the experimental hearts. However, mature coronary arterial formation was delayed. CONCLUSIONSThese observations further emphasize a direct and specific link between hypoxia and endocardial coronary vessel sprouting and suggest a role of hypoxia/VEGFA in guiding coronary arterial coalescence.

developmental biology↗

bioRxiv2026

A transcriptional code controlling fluid shear stress-induced gene expression

The formation and health of the vascular system is dependent on fluid shear stress (FSS), a hemodynamic force exerted onto endothelium by flowing blood. FSS strongly induces the endothelial expression of Kruppel-like factor 2 (KLF2), an atheroprotective TF essential for vascular development and homeostasis. Despite its early and crucial role in the cascade of cardiovascular events triggered by FSS, the transcriptional mechanisms by which FSS regulates KLF2 expression remain unclear, although they are known to involve the widely expressed MEF2 proteins. Here, we identified and characterized two FSS-dependent enhancers for KLF2 which collectively recapitulate endogenous endothelial KLF2 expression, and determined the TFs contributing to their regulation. This analysis identified an essential and precisely spaced MEF2-TBP double motif also shared by the FSS-sensitive KLF2 promoter. MEF-TBP double motifs are extremely rare across the genome but were also found within regulatory elements of three other FSS-induced KLF genes, including KLF4. Although normally part of the basal transcriptional machinery, TBP specifically bound all KLF elements at the MEF-TBP double motifs in a FSS-dependent manner. Collectively, this work demonstrates a specific and targetable requirement for combined MEF2-TBP binding during FSS-induced gene activation. Significance statementBlood flow induces a force known as fluid shear stress (FSS) which is required for vascular development and for the health of the mature arterial system. One of the first endothelial responses to FSS is the induction of Kruppel-like transcription factors (KLFs). However, the mechanisms by which FSS activates KLF gene expression are incompletely understood. In this paper, we characterized all regulatory elements involved in driving FSS-induced expression of KLF2. This identified an essential MEF2-TBP double motif that was extremely rare across the genome, yet found within regulatory elements for multiple FSS-responsive KLF genes including KLF2 and KLF4. This MEF2- and TBP-bound motif therefore enables blood flow to specifically activate the cascade of cardiovascular responses necessary for atheroprotective gene expression.

developmental biology↗

bioRxiv2025

A human arteriovenous differentiation roadmap reveals vein developmental mechanisms and vascular effects of viruses

Extracellular signals and cell-fate trajectories during vein development remain elusive, despite trailblazing insights into artery development. Here we exploit human pluripotent stem cell differentiation and mouse embryology to present a model that answers longstanding questions: vein endothelial cell (EC) differentiation unfolds in two steps driven by opposing extracellular signals. First, VEGF differentiates mesoderm into "primed" ECs, newly-defined progenitors that co-express certain arterial (SOX17) and venous (APLNR) markers. Second, primed ECs execute vein differentiation upon VEGF/ERK inhibition; however, upon VEGF activation they can instead form artery ECs. The arteriovenous plasticity of primed ECs was supported by intersectional lineage tracing. Future venous genes including NR2F2 harbor poised chromatin in primed ECs, but are only transcribed upon VEGF/ERK inhibition. SOXF transcription factors, including SOX17, confer primed ECs with vein differentiation competence. Collectively, this two-step vein differentiation model--entailing primed EC intermediates and VEGF/ERK inhibition to trigger vein differentiation--has implications for VEGF-modulating therapies.

developmental biology↗

bioRxiv2025

Context-dependent response of endothelial cells to PIK3CA mutation

Cancer mutations in the PIK3CA gene cause congenital disorders. The endothelium is among the most frequently affected tissues in these disorders, displaying aberrant vascular overgrowth in the form of malformations. Pathological PIK3CA vascular phenotypes are found in veins and capillaries but rarely in arteries for reasons that are unclear at present. Here, using lineage tracing, we show that expression of mutated PIK3CAH1047R in endothelial cells leads to marked clonal expansions in capillary and venous endothelial cells. In contrast, mature arterial endothelial cells are refractory to PIK3CA mutation under these conditions and never display pathological phenotypes. Moreover, PIK3CAH1047Rexpression in arterial precursors interrupts arterial differentiation, thereby driving fate switch towards venous identity. This fate rewiring offers an additional layer of protection to prevent arterial damage in response to PIK3CA genetic perturbation. Molecularly, the PIK3CAH1047R-driven arterial-to-venous fate switch is orchestrated by upregulation of the vein-specifying transcription factor Nr2f2/COUP-TFII. Our findings reveal that pathogenic responses to PIK3CAH1047Rgreatly depend on the diferentation stage and fate trajectory of the targeted cell. Arteries are thus shielded against PIK3CA mutation, solving the long-standing question on the rarity of PIK3CA-related arterial malformations observed in patients.

developmental biology↗

bioRxiv2024

A catalogue of verified and characterized arterial enhancers for key arterial identity genes.

The establishment and growth of the arterial endothelium requires the coordinated expression of numerous genes. However, the transcriptional and signalling pathways regulating this process are still not fully established, and only a small number of enhancers for key arterial genes have been characterized. Here, we sought to generate a useful and accessible cohort of arterial enhancers with which to study arterial transcriptional regulation. We combined in silico analysis with transgenic zebrafish and mouse models to find and validate enhancers associated with eight key arterial identity genes (Acvrl1/Alk1, Cxcr4, Cxcl12, Efnb2, Gja4/Cx37, Gja5/Cx40, Nrp1 and Unc5b). This identified a cohort of enhancers able to independently direct robust transcription to arterial ECs within the vasculature. To elucidate the regulatory pathways upstream of arterial gene transcription, we determined the occurrence of common endothelial transcription factor binding motifs, and assessed direct binding of these factors across all arterial enhancers compared to similar assessments of non-arterial-specific enhancers. These results find that binding of SOXF and ETS factors is a shared event across arterial enhancers, but also commonly occurs at pan-endothelial enhancers. Conversely, RBPJ/Notch, MEF2 and FOX binding was over-represented but not ubiquitous at arterial enhancers. We found no shared or arterial-specific signature for canonical WNT-associated TCF/LEF transcription factors, canonical TGF{beta}/BMP-associated SMAD1/5 and SMAD2, laminar shear stress-associated KLF factors or venous-enriched NR2F2 factors. This cohort of well characterized and in vivo-verified enhancers can now provide a platform for future studies into the interaction of different transcriptional and signalling pathways with arterial gene expression.

developmental biology↗

bioRxiv2021

Maternal iron deficiency impacts the placental arterial network.

Placental vascular gene networks in mammals have been largely unexplored due to a lack of well validated molecular markers to identify them. This is required to study how they form in development, and how they are impacted by embryonic or maternal defects, which in-turn adversely affects the forming heart and vasculature. Such defects are known to be a consequence of maternal iron deficiency (ID), the most common nutrient deficiency world-wide. Here we employed marker analysis to characterise the arterial/arteriole and venous/venule endothelial cells (ECs) during normal placental development, and in the context of maternal ID. We reveal for the first time that placental ECs are unique compared with their embryonic counterparts. In the developing embryo, arterial ECs express Neuropilin1 (Nrp1), Delta-like ligand 4 (Dll4) and Notch1, while developing venous ECs express Neuropilin2 (Nrp2), Apj (Aplnr) and Ephrinb4 (Ephb4). However, in the E15.5 placenta, Nrp1 and Notch1 were restricted to arteries, but not continuing arteriole ECs. The arterial tree exclusively expressed Dll4. Nrp2 showed pan-EC expression at E15.5, while Ephb4 was not present at this stage. However, we found the placental venous vascular tree could be distinguished from the arterial tree by high versus low Endomucin (EMCN) and Apj (Aplnr) expression respectively. Using EMCN, we reveal that the placental arterial, but not venous, vascular tree is adversely impacted by maternal ID, with reduced area, total length and number of junctions of all vessels without affecting the EMCN high vessels. Defects to the embryonic cardiovascular system can therefore have a significant impact on blood flow delivery and expansion of the placental arterial tree.

developmental biology↗

bioRxiv2020

JAG1-NOTCH4 MECHANOSENSING DRIVES ATHEROSCLEROSIS

Endothelial cell (EC) sensing of fluid shear stress regulates atherosclerosis, a disease of arteries that causes heart attack and stroke. Atherosclerosis preferentially develops at regions of arteries exposed to low oscillatory shear stress (LOSS), whereas high shear regions are protected. We show using inducible EC-specific genetic deletion in hyperlipidaemic mice that the Notch ligands JAG1 and DLL4 have opposing roles in atherosclerosis. While endothelial Jag1 promoted atherosclerosis at sites of LOSS, endothelial Dll4 was atheroprotective. Analysis of porcine and murine arteries and cultured human coronary artery EC exposed to experimental flow revealed that JAG1 and its receptor NOTCH4 are strongly upregulated by LOSS. Functional studies in cultured cells and in mice with EC-specific deletion of Jag1 show that JAG1-NOTCH4 signalling drives vascular dysfunction by repressing endothelial repair. These data demonstrate a fundamental role for JAG1-NOTCH4 in sensing LOSS during disease, and suggest therapeutic targeting of this pathway to treat atherosclerosis.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pathology↗

bioRxiv2019

Germline and somatic genetic variants in the p53 pathway interact to affect cancer risk, progression and drug response

Insights into oncogenesis derived from cancer susceptibility loci could facilitate better cancer management and treatment through precision oncology. However, therapeutic applications have thus far been limited by our current lack of understanding regarding both their interactions with somatic cancer driver mutations and their influence on tumorigenesis. Here, by integrating germline datasets relating to cancer susceptibility with tumour data capturing somatically-acquired genetic variation, we provide evidence that single nucleotide polymorphism (SNPs) and somatic mutations in the p53 tumor suppressor pathway can interact to influence cancer development, progression and treatment response. We go on to provide human genetic evidence of a tumor-promoting role for the pro-survival activities of p53, which supports the development of more effective therapy combinations through their inhibition in cancers retaining wild-type p53. SignificanceWe describe significant interactions between heritable and somatic genetic variants in the p53 pathway that affect cancer susceptibility, progression and treatment response. Our results offer evidence of how cancer susceptibility SNPs can interact with cancer driver genes to affect cancer progression and identify novel therapeutic targets.

cancer biology↗