Dll4-Notch信号传递途径在血管发生中的作用

血管发生(angiogenesis)依赖多种促进血管发生因子和抑制血管发生因子之综合的交互作用所调控。血管内皮生长因子(VEGF)和Notch信号传递途径(Notch signaling pathway)参与此过程。之前研究已证明Notch信号传递途径在胚胎发育和肿瘤血管发生(tumour angiogenesis)中扮演重要的角色,而最近研究则发现在血管发育过程中Dll4-Notch信号传递途径扮演着前所未知的新角色,并阐明因Notch信号传递减少而引起血管缺陷之机制,从而揭示破坏肿瘤血管发生的新药物靶点。本文着重于介绍Notch信号传递途径的组成;Dll4-Notch在血管发生中的作用;以及Dll4-Notch对肿瘤治疗的意义。     

丁苯酞通过激活VEGF/VEGFR2-Notch1/Dll4信号促进HUVECs形成血管

目的:探索缺血缺氧(H/I)条件下丁苯酞(NBP)通过激活血管内皮生长因子(VEGF)/VEGF受体2(VEGFR2)-Notch1/Delta样配体4(Dll4)信号促进人脐静脉内皮细胞(HUVECs)血管形成的机制。方法:利用无血清培养基和缺氧罐模拟H/I条件,HUVECs传代培养后设置正常对照(control)组、H/I组、NBP高剂量(H/I+NBP_(high))组和NBP低剂量(H/I+NBP_(low))组,其中control组为常规培养的HUVECs,H/I组为H/I条件下培养的HUVECs,H/I+NBP_(high)组为在H/I环境下使用20μmol/L丁苯酞干预的HUVECs,H/I+NBP_(low)组为在H/I环境下使用5μmol/L丁苯酞干预的HUVECs。CCK-8法检测各组细胞的细胞活力,细胞划痕实验检测各组细胞的迁移能力,体外血管形成实验检测各组细胞成管能力,Western blot法检测VEGFR2、Notch1和Dll4的表达,ELISA法检测培养基中VEGF的表达,qPCR检测VEGF、VEGFR2、Notch1和Dll4的mRNA表达水平。结果:丁苯酞可以提高H/I条件下HUVECs的存活率,促进细胞的迁移和体外血管的形成能力,且H/I+NBP_(high)组比H/I+NBP_(low)组更加显著。丁苯酞可以提高VEGF、VEGFR2、Notch1和Dll4的mRNA及蛋白表达。结论:丁苯酞可以在H/I条件下促进HUVECs形成血管,其机制可能与VEGF/VEGFR2-Notch1/Dll4信号的激活有关。     

Murine Notch1 is required for lymphatic vascular morphogenesis during development

BACKGROUND: The transmembrane receptor Notch1 is a critical regulator of arterial differentiation and blood vessel sprouting. Recent evidence shows that functional blockade of Notch1 and its ligand, Dll4, leads to postnatal lymphatic defects in mice. However, the precise role of the Notch signaling pathway in lymphatic vessel development has yet to be defined. Here we show the developmental role of Notch1 in lymphatic vascular morphogenesis by analyzing lymphatic endothelial cell (LEC)‐specific conditional Notch1 knockout mice crossed with an inducible Prox1CreER^T2 driver. RESULTS: LEC‐specific Notch1 mutant embryos exhibited enlarged lymphatic vessels. The phenotype of lymphatic overgrowth accords with increased LEC sprouting from the lymph sacs and increased filopodia formation. Furthermore, cell death was significantly reduced in Notch1‐mutant LECs, whereas proliferation was increased. RNA‐seq analysis revealed that expression of cytokine/chemokine signaling molecules was upregulated in Notch1‐mutant LECs isolated from E15.5 dorsal skin, whereas VEGFR3, VEGFR2, VEGFC, and Gja4 (Connexin 37) were downregulated. CONCLUSIONS: The lymphatic phenotype of LEC‐specific conditional Notch1 mouse mutants indicates that Notch activity in LECs controls lymphatic sprouting and growth during development. These results provide evidence that similar to postnatal and pathological lymphatic vessel formation, the Notch signaling pathway plays a role in inhibiting developmental lymphangiogenesis. Developmental Dynamics 243:957–964, 2014. © 2014 Wiley Periodicals, Inc.     

Expression of vascular Notch ligands Delta-like 4 and Jagged-1 in glioblastoma

Jubb A M, Browning L, Campo L, Turley H, Steers G, Thurston G, Harris A L & Ansorge O
(2012) Histopathology  60, 740–747
Expression of vascular Notch ligands Delta‐like 4 and Jagged‐1 in glioblastoma Aims: The coordinated expression of the Notch ligands Delta‐like 4 (Dll4) and Jagged (Jag)1 is believed to define appropriate endothelial sensitivity to vascular endothelial growth factor (VEGF). Preclinical data suggest that Dll4‐Notch signalling may confer resistance to anti‐VEGF therapy with bevacizumab, and Jag1 may antagonize Dll4–Notch. The aims of this study were to characterize the expression of Dll4 and Jag1 in primary glioblastomas. Methods and results: Immunohistochemistry was performed on 40 glioblastomas and normal brain using validated antibodies against Dll4 and Jag1. In‐situ hybridization for Dll4 was performed on serial sections and compared with protein expression. Dll4 expression was localized to the cytoplasm and membrane of endothelial cells in all glioblastomas; it was weak or absent in normal brain. Jag1 expression was observed in the cytoplasm and membrane of glomeruloid and non‐glomeruloid endothelial cells from 76% and 67% of glioblastomas, respectively. However, endothelial Jag1 expression was less intense and less prevalent than Dll4. There was no association between Dll4 and Jag1 expression. Conclusions: In summary, Dll4 and Jag1 are expressed in glioblastoma vasculature. These data may define subsets of glioblastoma that might be sensitive (Dll4⁺/Jag1⁺) or resistant (Dll4⁺/Jag1^–) to bevacizumab. Our data also suggest that anti‐Dll4 therapy should be evaluated experimentally in glioblastoma.     

Dosage-sensitive requirement for mouse Dll4 in artery development

Involvement of the Notch signaling pathway in vascular development has been demonstrated by both gain- and loss-of-function mutations in humans, mice, and zebrafish. In zebrafish, Notch signaling is required for arterial identity by suppressing the venous fate in developing artery cells. In mice, the Notch4 receptor and the Delta-like 4 (Dll4) ligand are specifically expressed in arterial endothelial cells, suggesting a similar role. Here we show that the Dll4 ligand alone is required in a dosage-sensitive manner for normal arterial patterning in development. This implicates Dll4 as the specific mammalian endothelial ligand for autocrine endothelial Notch signaling, and suggests that Dll4 may be a suitable target for intervention in arterial angiogenesis.     

Pitavastatin-induced angiogenesis and arteriogenesis is mediated by Notch1 in a murine hindlimb ischemia model without induction of VEGF

Notch signaling is reported to regulate angiogenesis, interacting with vascular endothelial growth factor (VEGF) signaling. HMG CoA reductase inhibitors (statins) also alter Notch signaling in vascular cells, but the mechanism and involvement of Notch and VEGF signaling in statin-mediated angiogenesis remain unclear. Here, we examined how statins activate the endothelial Notch1, and promote angiogenesis and arteriogenesis. We examined blood flow recovery after hindlimb ischemia in wild-type (WT) and Notch1 mutant mice treated with or without pitavastatin (3 mg/kg/day, p.o.). Although VEGF induction was not altered in ischemic limbs, pitavastatin promoted blood flow recovery in ischemic limbs in control mice but not in Notch1 mutant mice. Furthermore, pitavastatin induced endothelial ephrinB2 downstream of Notch1 and increased the density of both capillaries and arterioles in the ischemic limbs of WT but not of Notch1 mutant mice. Pitavastatin (100 nmol/l) rapidly activated γ-secretase and Notch1 in human umbilical vein endothelial cells without VEGF induction, which was suppressed by pharmacological inhibition and knockdown of Akt. Pitavastatin also augmented endothelial proliferation and tube formation on Matrigel, which were suppressed by either γ-secretase inhibition or knockdown of Notch1. Pitavastatin-induced microvascular sprouting was also impaired in Notch1 mutant aortic explants. Taken together, pitavastatin activates Notch1 through Akt-dependent stimulation of γ-secretase in endothelial cells, and thereby increases vasculogenesis without VEGF induction.     

消肿止痛合剂对大鼠随意皮瓣血管再生的影响

目的:观察消肿止痛合剂对大鼠随意皮瓣血管再生及血管内皮生长因子(VEGF)-Dll4/Notch信号通路的影响.方法:将240只健康SD大鼠随机分为6组,分别为空白组、假手术组、模型组、消肿止痛合剂组(消肿组)、消肿止痛合剂+Notch阻断剂MK-0752(MK)组(消肿+MK组)和消肿止痛合剂组+VEGF受体抑制剂a...     

Regulation of endothelial cell differentiation and arterial specification by VEGF and Notch signaling

Analysis of molecular and cellular mechanisms underlying vascular development in vertebrates indicates that initially vasculogenesis occurs when a primary capillary plexus forms de novo from endothelial cell precursors derived from nascent mesodermal cells. Transplantation experiments in avian embryos demonstrate that embryonic endothelial cells originate from two different mesodermal lineages: splanchnic mesoderm and somites. Genetic analysis of mouse and zebrafish reveals that vascular endothelial growth factor (VEGF)/Flk1 and Notch signaling play crucial roles throughout embryonic vascular development. VEGFA plays a major role in endothelial cell proliferation, migration, survival, and regulation of vascular permeability. Flk1, the primary VEGFA receptor, is the earliest marker of the developing endothelial lineage and is essential for endothelial differentiation during vasculogenesis. Notch signaling has been demonstrated to directly induce arterial endothelial differentiation. Recent studies suggest that Notch signaling is activated downstream of VEGF signaling and negatively regulates VEGF-induced angiogenesis and suppresses aberrant vascular branching morphogenesis. In addition to altering endothelial cell fate through Notch activation, VEGFA directly guides endothelial cell migration in an isoform-dependent manner, modifying vascular patterns. Interestingly, genetic studies in mice show that many molecules involved in VEGF or Notch signaling must be tightly regulated for proper vascular formation. Taken together, VEGF and Notch signaling apparently coordinate vascular patterning by regulating each other.     

Ongoing Dll4-Notch signaling is required for T-cell homeostasis in the adult thymus

The essential role of the Delta-like ligand 4 (Dll4)-Notch signaling pathway in T-lymphocyte development is well established. It has been shown that specific inactivation of Dll4 on thymic stromal cells during early post-natal development leads to a deregulation in T-cell differentiation. However, whether ongoing Dll4-Notch signaling is required for T-cell development in the adult thymus is unknown. The use of anti-Dll4 Abs allowed us to confirm and expand previous studies by examining the kinetics and the reversibility of Dll4-Notch signaling blockade in T-cell development in adult mice. We found that anti-Dll4 treatment reduced thymic cellularity after 7 days, as a consequence of a developmental delay in T-cell maturation at the pro-T-cell double negative 1 (CD4(-) CD8(-) c-kit(+) CD44(+) CD25(-) ) stage, leading to decreased numbers of immature double-positive (CD4(+) CD8(+) ) T cells without affecting the frequency of mature single positive CD4(+) and CD8(+) thymocytes, while promoting alternative thymic B-cell expansion. This cellular phenotype was similarly observed in both young adult and aged mice (>1.5 years), extending our understanding of the ongoing role for Dll4-Notch signaling during T-cell development in the adult thymus. Finally, after cessation of Dll4 Ab treatment, thymic cellularity and thymocyte subset ratios returned to normal levels, indicating reversibility of this phenotype in both adult and aged mice, which has important implications for potential clinical use of Dll4-Notch inhibitors.     

Dll3 and Notch1 genetic interactions model axial segmental and craniofacial malformations of human birth defects.

Mutations in the Notch1 receptor and delta-like 3 (Dll3) ligand cause global disruptions in axial segmental patterning. Genetic interactions between members of the notch pathway have previously been shown to cause patterning defects not observed in single gene disruptions. We examined Dll3-Notch1 compound mouse mutants to screen for potential gene interactions. While mice heterozygous at either locus appeared normal, 30% of Dll3-Notch1 double heterozygous animals exhibited localized, segmental anomalies similar to human congenital vertebral defects. Unexpectedly, double heterozygous mice also displayed statistically significant reduction of mandibular height and decreased length of the [corrected] maxillary hard palate. Examination of somite-stage embryos and perinatal anatomy and histology did not reveal any organ defects, so we used microarray-based analysis of Dll3 and Notch1 mutant embryos to identify gene targets that may be involved in notch-regulated segmental or craniofacial development. Thus, Dll3-Notch1 double heterozygous mice model human congenital scoliosis and craniofacial disorders.     

Relationship between Delta-like and proneural bHLH genes during chick retinal development.

Notch signaling in the retina maintains a pool of progenitor cells throughout retinogenesis. However, two Notch-ligands from the Delta-like gene family, Dll1 and Dll4, are present in the developing retina. To understand their relationship, we characterized Dll1 and Dll4 expression with respect to proliferating progenitor cells and newborn neurons in the chick retina. Dll4 matched the pattern of neural differentiation. By contrast, Dll1 was primarily expressed in progenitor cells. We compared Dll1 and Dll4 kinetic profiles with that of the transiently up-regulated cascade of proneural basic helix-loop-helix (bHLH) genes after synchronized progenitor cell differentiation, which suggested a potential role for Ascl1 in the regulation of Delta-like genes. Gain-of-function assays demonstrate that Ascl1 does influence Delta-like gene expression and Notch signaling activity. These data suggest that multiple sources of Notch signaling from newborn neurons and progenitors themselves coordinate retinal histogenesis.     

Semaphorin 3E-Plexin-D1 signaling controls pathway-specific synapse formation in the striatum

The proper formation of synaptic connectivity in the mammalian brain is critical for complex behavior. In the striatum, balanced excitatory synaptic transmission from multiple sources onto two classes of principal neurons is required for coordinated and voluntary motor control. Here we show that the interaction between the secreted semaphorin 3E (Sema3E) and its receptor Plexin-D1 is a critical determinant of synaptic specificity in cortico-thalamo-striatal circuits in mice. We find that Sema3e (encoding Sema3E) is highly expressed in thalamostriatal projection neurons, whereas in the striatum Plxnd1 (encoding Plexin-D1) is selectively expressed in direct-pathway medium spiny neurons (MSNs). Despite physical intermingling of the MSNs, genetic ablation of Plxnd1 or Sema3e results in functional and anatomical rearrangement of thalamostriatal synapses specifically in direct-pathway MSNs without effects on corticostriatal synapses. Thus, our results demonstrate that Sema3E and Plexin-D1 specify the degree of glutamatergic connectivity between a specific source and target in the complex circuitry of the basal ganglia.     

Delta‐like 4‐mediated Notch signaling is required for early T‐cell development in a three‐dimensional thymic structure

Delta‐like 4 (Dll4)‐mediated Notch signaling is critical for specifying T‐cell fate, but how Dll4‐mediated Notch signaling actually contributes to T‐cell development in the thymus remains unclear. To explore this mechanism in the thymic three‐dimensional structure, we performed fetal thymus organ culture using Dll4‐deficient mice. DN1a/b+DN2mt cells, which had not yet committed to either the αβ T or γδ T/NK cell lineage, did not differentiate into the αβ T‐cell lineage in Dll4‐deficient thymus despite the lack of cell fate conversion into other lineages. However, DN3 cells efficiently differentiated into a later developmental stage of αβ T cells, the double‐positive (DP) stage, although the proliferation was significantly impaired during the differentiation process. These findings suggest that the requirement for Notch signaling differs between the earliest and pre‐TCR‐bearing precursors and that continued Notch signaling is required for proper differentiation with active proliferation of αβ T lineage cells. Furthermore, we showed that Notch signaling increased the c‐Myc expression in DN3 cells in the thymus and that its overexpression rescued the proliferation and differentiation of DN3 cells in the Dll4‐null thymus. Therefore, c‐Myc plays a central role in the transition from stage DN3 to DP as a downstream target of Notch signaling.     

ERK activation in endothelial cells is a novel marker during neovasculogenesis

Vasculogenesis is essential during early development to construct networks transporting oxygen, blood and nutrients. Tip and stalk cells are specialized endothelial cells involved in novel vessel formation because of their behavior such as sprouting as a leading cell and following tip cell. However, the spatiotemporal details determining the emergence of these cells are unknown. Here, we first show that the ERK activity in endothelial cells represents the precursor of tip and stalk cells for vasculogenesis in zebrafish. We identified that tip and stalk cells for intersegmental vessel (ISV) formation were already specialized in the dorsal aorta (DA) before sprouting. Furthermore, similar specialization was observed in tip cells during parachordal vessel (PAV) formation in lymphangiogenesis. We also identified that the ERK activity was required for specialized cells to emerge from existing blood vessels. Our data show that the ERK activity is a novel marker for determining the emergence of cells in both angiogenesis and lymphangiogenesis.     

Regulation of angiogenesis by vascular endothelial growth factor and angiopoietin-1 in the rat aorta model: distinct temporal patterns of intracellular signaling correlate with induction of angiogenic sprouting

Vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) promote the spontaneous angiogenic response of freshly cut rat aortic rings. When VEGF and Ang-1 were tested in cultures of 14-day-old rings, which are quiescent and unable to spontaneously produce neovessels, only VEGF was capable of inducing an angiogenic response. Ang-1 failed to initiate angiogenesis in this system, but significantly potentiated VEGF-induced neovessel sprouting. Potential differences in cell signaling triggered by VEGF and Ang-1 were evaluated in cultures of quiescent rings. VEGF induced biphasic and prolonged (15 minutes and 4 to 24 hours) phosphorylation of p44/42 MAPK and Akt, while the effect of Ang-1 was transient and monophasic (15 minutes). Both VEGF and Ang-1 induced rapid, monophasic (15 minutes) phosphorylation of p38 MAPK. When VEGF and Ang-1 were administered together, the second peak of VEGF-induced p44/42 MAPK phosphorylation was markedly reduced. The effect of the VEGF/Ang-1 combination on AKT phosphorylation was, instead, additive over time, and sustained over a 24-hour period. The VEGF/Ang-1 combination caused an additive effect also on p38 MAPK phosphorylation at 1 hour. Confocal microscopy of VEGF-, Ang-1, or VEGF/Ang-1-stimulated aortic rings double stained at time points of maximal phosphorylation for cell markers and signal transduction proteins demonstrated phosphorylated p44/42 MAPK, p38 MAPK, and Akt predominantly in endothelial cells. Experiments with specific inhibitors demonstrated that p44/42 MAPK and Akt, but not p38 MAPK, are necessary for neovessel sprouting. These results identify p44/42 MAPK and Akt as critical intracellular mediators of angiogenesis, whose transient phosphorylation is, however, not sufficient for the initiation of this process. The observation that sustained phosphorylation of these signaling pathways, particularly of Akt, correlates with induction of angiogenesis suggests that the duration of phosphorylation signals influences critical cellular events required for the induction of angiogenic sprouting.     

Cell autonomous and nonautonomous requirements for Delltalike1 during early mouse retinal neurogenesis

Background: In the vertebrate retina, six neuronal and one glial cell class are produced from a common progenitor pool. During neurogenesis, adjacent retinal cells use Notch signaling to maintain a pool of progenitors by blocking particular cells from differentiating prematurely. In mice there are multiple Notch pathway ligands and receptors, but the role(s) of each paralogue during retinal histogenesis remains only partially defined. Results: Here we analyzed the cell autonomous and nonautonomous requirements for the Deltalike1(Dll1) ligand during prenatal retinogenesis. We used the α‐Cre driver to simultaneously delete a Dll1 conditional allele and activate the Z/EG reporter, then quantified Dll1 mutant phenotypes within and outside of this α‐Cre GFP‐marked lineage. We found that Dll1 activity is required for Hes1 expression, both autonomously and nonautonomously, but were surprised that retinal ganglion cell differentiation is only blocked cell autonomously. Moreover, Dll1 does not act during cone photoreceptor neurogenesis. Finally, Dll1 mutant adult retinas contained small retinal rosettes and RGC patterning defects but were otherwise normal. Conclusions: Although Dll1 participates in bidirectional (cis + trans) Notch signaling to regulate Hes1 expression, it only acts cell autonomously (in cis) to interpret inhibitory signals from other cells that block RGC neurogenesis. Developmental Dynamics 245:631–640, 2016. © 2016 Wiley Periodicals, Inc.     

Selective neuronal lineages derived from Dll4‐expressing progenitors/precursors in the retina and spinal cord

Results: We generated a Dll4‐Cre BAC transgenic mouse line that drives Cre recombinase expression mimicking that of the endogenous Dll4 in the developing retina and spinal cord. By fate‐mapping analysis, we found that Dll4‐expressing progenitors/precursors give rise to essentially all cone, amacrine and horizontal cells, a large portion of rod and ganglion cells, but only few bipolar and Müller cells. In the spinal cord, Dll4‐expressing progenitors/precursors generate almost all V2a and V2c cells while producing only a fraction of the cells for other interneuron and motor neuron subtypes along the dorsoventral axis. 相似文献