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Notch ligand Dll4 impairs cell recruitment to aortic clusters and limits blood stem cell generation.

ABSTRACT: Hematopoietic stem cells (HSCs) develop from the hemogenic endothelium in cluster structures that protrude into the embryonic aortic lumen. Although much is known about the molecular characteristics of the developing hematopoietic cells, we lack a complete understanding of their origin and the three-dimensional organization of the niche. Here, we use advanced live imaging techniques of organotypic slice cultures, clonal analysis, and mathematical modeling to show the two-step process of intra-aortic hematopoietic cluster (IACH) formation. First, a hemogenic progenitor buds up from the endothelium and undergoes division forming the monoclonal core of the IAHC. Next, surrounding hemogenic cells are recruited into the IAHC, increasing their size and heterogeneity. We identified the Notch ligand Dll4 as a negative regulator of the recruitment phase of IAHC. Blocking of Dll4 promotes the entrance of new hemogenic Gfi1⁺ cells into the IAHC and increases the number of cells that acquire HSC activity. Mathematical modeling based on our data provides estimation of the cluster lifetime and the average recruitment time of hemogenic cells to the cluster under physiologic and Dll4-inhibited conditions.

SUBMITTER: Porcheri C

PROVIDER: S-EPMC7156969 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production

Project description:Hematopoietic stem cells (HSCs) develop from the hemogenic endothelium in the embryonic aorta. In most vertebrates, hemogenic cells protrude into the aortic lumen forming clusters where the hematopoietic features are acquired. Although much is known about the molecular characteristics of the hematopoietic cells, we still lack basic understanding on the origin and 3D-organization of intraortic hematopoietic clusters (IAHC) in the mouse embryo and how they evolve over time. Here we use advanced live imaging techniques of organotypic slice cultures, clonal analysis, and mathematical modelling to show that IAHC formation is a two-step process. First, a hemogenic progenitor buds up from the endothelium and undergoes division forming the monoclonal core of the cluster. Next, cells from the surrounding hemogenic endothelium are recruited into the IAHCs, increasing their size and heterogeneity. We found that the recruitment phase of IAHC formation is negatively regulated by Notch signalling via the Delta-like-4 (Dll4) Notch ligand. We show that blocking of Dll4 promotes the entrance of new hemogenic Gfi1+ cells into the IAHC and increases the number of cells that acquire HSC activity. Mathematical modelling based on our data provides estimation of the cluster lifetime and the average recruitment time of hemogenic cells to the cluster under physiologic and Dll4-inhibited conditions. Single cell transcriptomic analysis indicates that cell identities are preserved after Dll4 blockage. Our data provides for the first time a detailed characterization of the aortic hematopoietic stem cell niche and its maturation dynamics, identifying the Notch ligand Dll4 as a major molecular player governing dynamics of cluster formation and HSCs production.

2020-02-03 | GSE124477 | GEO

Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production.

2020-01-10 | GSE124875 | GEO

Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production.

Project description:Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production.

| PRJNA514056 | ENA

Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production

Project description:Notch ligand Dll4 impairs the recruitment of hemogenic cells into intra-aortic clusters and limits hematopoietic stem cell production

| PRJNA512128 | ENA

Endothelial basement membrane limits tip cell formation by inducing Dll4/Notch signalling in vivo.

Project description:How individual components of the vascular basement membrane influence endothelial cell behaviour remains unclear. Here we show that laminin ?4 (Lama4) regulates tip cell numbers and vascular density by inducing endothelial Dll4/Notch signalling in vivo. Lama4 deficiency leads to reduced Dll4 expression, excessive filopodia and tip cell formation in the mouse retina, phenocopying the effects of Dll4/Notch inhibition. Lama4-mediated Dll4 expression requires a combination of integrins in vitro and integrin ?1 in vivo. We conclude that appropriate laminin/integrin-induced signalling is necessary to induce physiologically functional levels of Dll4 expression and regulate branching frequency during sprouting angiogenesis in vivo.

| S-EPMC3207109 | biostudies-literature

Dll4, a novel Notch ligand expressed in arterial endothelium.

Project description:We report the cloning and characterization of a new member of the Delta family of Notch ligands, which we have named Dll4. Like other Delta genes, Dll4 is predicted to encode a membrane-bound ligand, characterized by an extracellular region containing several EGF-like domains and a DSL domain required for receptor binding. In situ analysis reveals a highly selective expression pattern of Dll4 within the vascular endothelium. The activity and expression of Dll4 and the known actions of other members of this family suggest a role for Dll4 in the control of endothelial cell biology.

| S-EPMC316657 | biostudies-literature

Identification of Notch ligand useage by splenic B cells using Dll1 and Dll4 Notch ligand blockade.

Project description:Marginal zone (MZ) B cells leverage Notch2 signals to attain rapid differentiation responses and positional cues with in the spenic environment.To determine the likely molecular source of Notch2 signals we sought to block the Notch ligands delta-like ligand 1 (Dll1) and delta-like ligand 4 (Dll4) in wildtype mice using in-vivo treatment with monoclonal blocking antibodies. Splenic populations of MZ B cells and follicular B cells were sort purified after 12, 24 and 48 hours of blockade and analyzed by RNA-seq.

2024-10-18 | GSE274991 | GEO

Spatial patterning of the Notch ligand Dll4 controls endothelial sprouting in vitro.

Project description:Angiogenesis, the formation of new blood vessels, is a vital process for tissue growth and development. The Notch cell-cell signalling pathway plays an important role in endothelial cell specification during angiogenesis. Dll4 - Notch1 signalling directs endothelial cells into migrating tip or proliferating stalk cells. We used the directing properties of Dll4 to spatially control endothelial cell fate and the direction of endothelial sprouts. We created linear arrays of immobilized Dll4 using micro contact printing. HUVECs were seeded perpendicular to these Dll4 patterns using removable microfluidic channels. The Notch activating properties of surface immobilized Dll4 were confirmed by qPCR. After induction of sprouting, microscopic images of fluorescently labelled endothelial sprouts were analysed to determine the direction and the efficiency of controlled sprouting (Ecs). Directionality analysis of the sprouts showed the Dll4 pattern changes sprout direction from random to unidirectional. This was confirmed by the increase of Ecs from 54.5 ± 3.1% for the control, to an average of 84.7 ± 1.86% on the Dll4 patterned surfaces. Our data demonstrates a surface-based method to spatially pattern Dll4 to gain control over endothelial sprout location and direction. This suggests that spatial ligand patterning can be used to provide control over (neo) vascularization.

| S-EPMC5913301 | biostudies-literature

Notch Ligand DLL4 Alleviates Allergic Airway Inflammation via Induction of a Homeostatic Regulatory Pathway.

Project description:Notch is a pleiotropic signaling family that has been implicated in pathogenesis of allergic airway diseases; however, the distinct function of individual Notch ligands remains elusive. We investigated whether Notch ligands, Jagged1 and DLL4, exert differential effects in OVA-induced allergic asthma. We found that whilst Jagged1 inhibition mitigated Th2-dominated airway inflammation, blockage of DLL4 aggravated the Th2-mediated asthma phenotypes. Additionally, Jagged1 signaling blockage enhanced IL-17 production and neutrophilic airway infiltration. In vitro, exogenous Jagged1 induced Th2-skewed responses, whereas augmented DLL4 signaling displayed a dual role by promoting expansion of both Tregs and Th17. In vivo, DLL4 blockage impaired Treg differentiation which plausibly resulted in exaggerated asthma phenotypes. On the contrary, administration of DLL4-expressing antigen-presenting cells promoted endogenous Treg expansion and ameliorated the allergic responses. Therefore, whilst Jagged1 induces Th2-skewed inflammation, DLL4 elicits an essential self-regulatory mechanism via Treg-mediated pathway that counterbalances Jagged1-induced Th2 responses and facilitates resolution of the airway inflammation to restore homeostasis. These findings uncover a disparate function of Jagged1 and DLL4 in allergic airway diseases, hinting feasibility of Notch ligand-specific targeting in therapy of allergic airway diseases.

| S-EPMC5337933 | biostudies-literature

The Notch Ligand DLL4 Defines a Capability of Human Dendritic Cells in Regulating Th1 and Th17 Differentiation.

Project description:Notch signaling regulates multiple helper CD4(+) T cell programs. We have recently demonstrated that dendritic cells (DCs) expressing the Notch ligand DLL4 are critical for eliciting alloreactive T cell responses and induction of graft-versus-host disease in mice. However, the human counterpart of murine DLL4(+) DCs has yet to be examined. We report the identification of human DLL4(+) DCs and their critical role in regulating Th1 and Th17 differentiation. CD1c(+) DCs and plasmacytoid DCs (pDCs) from the peripheral blood (PB) of healthy donors did not express DLL4. In contrast, patients undergoing allogeneic hematopoietic stem cell transplantation had a 16-fold more DLL4(+)CD1c(+) DCs than healthy donors. Upon activation of TLR signaling, healthy donor-derived CD1c(+) DCs dramatically upregulated DLL4, as did pDCs to a lesser extent. Activated DLL4(+) DCs were better able to promote Th1 and Th17 differentiation than unstimulated PB DCs. Blocking DLL4 using a neutralizing Ab decreased Notch signaling in T cells stimulated with DLL4(+) DCs, and it reduced the generation of Th1 and Th17 cells. Both NF-?B and STAT3 were crucial for inducing DLL4 in human DCs. Interestingly, STAT3 directly activated DLL4 transcription and inhibiting STAT3 alone was sufficient to reduce DLL4 in activated PB DCs. Thus, DLL4 is a unique functional molecule of human circulating DCs critical for directing Th1 and Th17 differentiation. These findings identify a pathway for therapeutic intervention for inflammatory disorders in humans, such as graft-versus-host disease after allogeneic hematopoietic stem cell transplantation, autoimmunity, and tumor immunity.

| S-EPMC4930627 | biostudies-literature

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