RESUMO
Mammals have two specialized vascular circulatory systems: the blood vasculature and the lymphatic vasculature. The lymphatic vasculature is a unidirectional conduit that returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays major roles in immune cell trafficking and lipid absorption. As we discuss in this review, the molecular characterization of lymphatic vascular development and our understanding of this vasculature's role in pathophysiological conditions has greatly improved in recent years, changing conventional views about the roles of the lymphatic vasculature in health and disease. Morphological or functional defects in the lymphatic vasculature have now been uncovered in several pathological conditions. We propose that subtle asymptomatic alterations in lymphatic vascular function could underlie the variability seen in the body's response to a wide range of human diseases.
Assuntos
Vasos Linfáticos/metabolismo , Doenças Cardiovasculares/metabolismo , Doenças Cardiovasculares/patologia , História do Século XXI , Humanos , Linfonodos/imunologia , Linfonodos/metabolismo , Linfangiogênese , Doenças Linfáticas/genética , Doenças Linfáticas/história , Doenças Linfáticas/patologia , Metástase Linfática , Vasos Linfáticos/anatomia & histologia , Vasos Linfáticos/citologia , Neoplasias/metabolismo , Neoplasias/patologia , Receptor 3 de Fatores de Crescimento do Endotélio Vascular/genéticaRESUMO
Transcriptional enhancer elements are responsible for orchestrating the temporal and spatial control over gene expression that is crucial for programming cell identity during development1-3. Here we describe a novel enhancer element that is important for regulating the expression of Prox1 in lymphatic endothelial cells. This evolutionarily conserved enhancer is bound by key lymphatic transcriptional regulators including GATA2, FOXC2, NFATC1 and PROX1. Genome editing of the enhancer to remove five nucleotides encompassing the GATA2-binding site resulted in perinatal death of homozygous mutant mice due to profound lymphatic vascular defects. Lymphatic endothelial cells in enhancer mutant mice exhibited reduced expression of genes characteristic of lymphatic endothelial cell identity and increased expression of genes characteristic of haemogenic endothelium, and acquired the capacity to generate haematopoietic cells. These data not only reveal a transcriptional enhancer element important for regulating Prox1 expression and lymphatic endothelial cell identity but also demonstrate that the lymphatic endothelium has haemogenic capacity, ordinarily repressed by Prox1.
Assuntos
Células Endoteliais , Elementos Facilitadores Genéticos , Hematopoese , Vasos Linfáticos , Animais , Camundongos , Células Endoteliais/metabolismo , Elementos Facilitadores Genéticos/genética , Hematopoese/genética , Proteínas de Homeodomínio/metabolismo , Vasos Linfáticos/citologia , Vasos Linfáticos/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Despite a growing catalog of secreted factors critical for lymphatic network assembly, little is known about the mechanisms that modulate the expression level of these molecular cues in blood vascular endothelial cells (BECs). Here, we show that a BEC-specific transcription factor, SOX7, plays a crucial role in a non-cell-autonomous manner by modulating the transcription of angiocrine signals to pattern lymphatic vessels. While SOX7 is not expressed in lymphatic endothelial cells (LECs), the conditional loss of SOX7 function in mouse embryos causes a dysmorphic dermal lymphatic phenotype. We identify novel distant regulatory regions in mice and humans that contribute to directly repressing the transcription of a major lymphangiogenic growth factor (Vegfc) in a SOX7-dependent manner. Further, we show that SOX7 directly binds HEY1, a canonical repressor of the Notch pathway, suggesting that transcriptional repression may also be modulated by the recruitment of this protein partner at Vegfc genomic regulatory regions. Our work unveils a role for SOX7 in modulating downstream signaling events crucial for lymphatic patterning, at least in part via the transcriptional repression of VEGFC levels in the blood vascular endothelium.
Assuntos
Células Endoteliais , Vasos Linfáticos , Humanos , Camundongos , Animais , Células Endoteliais/metabolismo , Vasos Linfáticos/metabolismo , Regulação da Expressão Gênica , Endotélio Vascular , Fatores de Transcrição/metabolismo , Linfangiogênese/genética , Fatores de Transcrição SOXF/genética , Fatores de Transcrição SOXF/metabolismoRESUMO
During embryonic development, lymphatic endothelial cell (LEC) precursors are distinguished from blood endothelial cells by the expression of Prospero-related homeobox 1 (Prox1), which is essential for lymphatic vasculature formation in mouse and zebrafish. Prox1 expression initiation precedes LEC sprouting and migration, serving as the marker of specified LECs. Despite its crucial role in lymphatic development, Prox1 upstream regulation in LECs remains to be uncovered. SOX18 and COUP-TFII are thought to regulate Prox1 in mice by binding its promoter region. However, the specific regulation of Prox1 expression in LECs remains to be studied in detail. Here, we used evolutionary conservation and chromatin accessibility to identify enhancers located in the proximity of zebrafish prox1a active in developing LECs. We confirmed the functional role of the identified sequences through CRISPR/Cas9 mutagenesis of a lymphatic valve enhancer. The deletion of this region results in impaired valve morphology and function. Overall, our results reveal an intricate control of prox1a expression through a collection of enhancers. Ray-finned fish-specific distal enhancers drive pan-lymphatic expression, whereas vertebrate-conserved proximal enhancers refine expression in functionally distinct subsets of lymphatic endothelium.
Assuntos
Células Endoteliais , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio , Vasos Linfáticos , Proteínas Supressoras de Tumor , Proteínas de Peixe-Zebra , Peixe-Zebra , Animais , Proteínas de Homeodomínio/metabolismo , Proteínas de Homeodomínio/genética , Peixe-Zebra/genética , Peixe-Zebra/embriologia , Proteínas Supressoras de Tumor/metabolismo , Proteínas Supressoras de Tumor/genética , Elementos Facilitadores Genéticos/genética , Vasos Linfáticos/metabolismo , Vasos Linfáticos/embriologia , Proteínas de Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Células Endoteliais/metabolismo , Linfangiogênese/genética , Sistemas CRISPR-Cas/genética , Regiões Promotoras Genéticas/genética , CamundongosRESUMO
The lymphatic vasculature is an integral component of the cardiovascular system. It is essential to maintain tissue fluid homeostasis, direct immune cell trafficking and absorb dietary lipids from the digestive tract. Major advances in our understanding of the genetic and cellular events important for constructing the lymphatic vasculature during development have recently been made. These include the identification of novel sources of lymphatic endothelial progenitor cells, the recognition of lymphatic endothelial cell specialisation and heterogeneity, and discovery of novel genes and signalling pathways underpinning developmental lymphangiogenesis. Here, we review these advances and discuss how they inform our understanding of lymphatic network formation, function and dysfunction.
Assuntos
Sistema Cardiovascular/crescimento & desenvolvimento , Linfangiogênese/fisiologia , Vasos Linfáticos/fisiologia , Animais , Sistema Cardiovascular/citologia , Sistema Cardiovascular/embriologia , Células Endoteliais/fisiologia , Homeostase , Humanos , Vasos Linfáticos/citologia , Vasos Linfáticos/embriologia , Transdução de SinaisRESUMO
BACKGROUND: Lymphatic vascular development is regulated by well-characterized signaling and transcriptional pathways. These pathways regulate lymphatic endothelial cell (LEC) migration, motility, polarity, and morphogenesis. Canonical and non-canonical WNT signaling pathways are known to control LEC polarity and development of lymphatic vessels and valves. PKD1, encoding Polycystin-1, is the most commonly mutated gene in polycystic kidney disease but has also been shown to be essential in lymphatic vascular morphogenesis. The mechanism by which Pkd1 acts during lymphangiogenesis remains unclear. RESULTS: Here we find that loss of non-canonical WNT signaling components Wnt5a and Ryk phenocopy lymphatic defects seen in Pkd1 knockout mice. To investigate genetic interaction, we generated Pkd1;Wnt5a double knockout mice. Loss of Wnt5a suppressed phenotypes seen in the lymphatic vasculature of Pkd1-/- mice and Pkd1 deletion suppressed phenotypes observed in Wnt5a-/- mice. Thus, we report mutually suppressive roles for Pkd1 and Wnt5a, with developing lymphatic networks restored to a more wild type state in double mutant mice. This genetic interaction between Pkd1 and the non-canonical WNT signaling pathway ultimately controls LEC polarity and the morphogenesis of developing vessel networks. CONCLUSION: Our work suggests that Pkd1 acts at least in part by regulating non-canonical WNT signaling during the formation of lymphatic vascular networks.
Assuntos
Vasos Linfáticos , Doenças Renais Policísticas , Animais , Vasos Linfáticos/metabolismo , Camundongos , Camundongos Knockout , Morfogênese/genética , Doenças Renais Policísticas/genética , Doenças Renais Policísticas/metabolismo , Proteína Quinase C , Receptores Proteína Tirosina Quinases/metabolismo , Via de Sinalização Wnt/genética , Proteína Wnt-5a/genética , Proteína Wnt-5a/metabolismoRESUMO
GATA2 deficiency syndrome (G2DS) is a rare autosomal dominant genetic disease predisposing to a range of symptoms, of which myeloid malignancy and immunodeficiency including recurrent infections are most common. In the last decade since it was first reported, there have been over 480 individuals identified carrying a pathogenic or likely pathogenic germline GATA2 variant with symptoms of G2DS, with 240 of these confirmed to be familial and 24 de novo. For those that develop myeloid malignancy (75% of all carriers with G2DS disease symptoms), the median age of onset is 17 years (range 0-78 years) and myelodysplastic syndrome is the first diagnosis in 75% of these cases with acute myeloid leukemia in a further 9%. All variant types appear to predispose to myeloid malignancy and immunodeficiency. Apart from lymphedema in which haploinsufficiency seems necessary, the mutational requirements of the other less common G2DS phenotypes is still unclear. These predominantly loss-of-function variants impact GATA2 expression and function in numerous ways including perturbations to DNA binding, protein structure, protein:protein interactions, and gene transcription, splicing, and expression. In this review, we provide the first expert-curated ACMG/AMP classification with codes of published variants compatible for use in clinical or diagnostic settings.
Assuntos
Deficiência de GATA2/genética , Fator de Transcrição GATA2/genética , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Estudos de Coortes , Humanos , Lactente , Recém-Nascido , Pessoa de Meia-Idade , Adulto JovemRESUMO
Despite the essential role of the lymphatic vasculature in tissue homeostasis and disease, knowledge of the organ-specific origins of lymphatic endothelial progenitor cells remains limited. The assumption that most murine embryonic lymphatic endothelial cells (LECs) are venous derived has recently been challenged. Here, we show that the embryonic dermal blood capillary plexus constitutes an additional, local source of LECs that contributes to the formation of the dermal lymphatic vascular network. We describe a novel mechanism whereby rare PROX1-positive endothelial cells exit the capillary plexus in a Ccbe1-dependent manner to establish discrete LEC clusters. As development proceeds, these clusters expand and further contribute to the growing lymphatic system. Lineage tracing and analyses of Gata2-deficient mice confirmed that these clusters are endothelial in origin. Furthermore, ectopic expression of Vegfc in the vasculature increased the number of PROX1-positive progenitors within the capillary bed. Our work reveals a novel source of lymphatic endothelial progenitors employed during construction of the dermal lymphatic vasculature and demonstrates that the blood vasculature is likely to remain an ongoing source of LECs during organogenesis, raising the question of whether a similar mechanism operates during pathological lymphangiogenesis.
Assuntos
Capilares/citologia , Células Endoteliais/citologia , Proteínas de Homeodomínio/genética , Linfangiogênese/fisiologia , Vasos Linfáticos/embriologia , Células-Tronco/citologia , Proteínas Supressoras de Tumor/genética , Animais , Proteínas de Ligação ao Cálcio/genética , Fator de Transcrição GATA2/genética , Linfangiogênese/genética , Vasos Linfáticos/citologia , Camundongos , Camundongos Transgênicos , Fator C de Crescimento do Endotélio Vascular/biossíntese , Fator C de Crescimento do Endotélio Vascular/genéticaRESUMO
The importance of lymphatic vessels in a myriad of human diseases is rapidly gaining recognition; lymphatic vessel dysfunction is a feature of disorders including congenital lymphatic anomalies, primary lymphoedema and obesity, while improved lymphatic vessel function increases the efficacy of immunotherapy for cancer and neurological disease and promotes cardiac repair following myocardial infarction. Understanding how the growth and function of lymphatic vessels is precisely regulated therefore stands to inform the development of novel therapeutics applicable to a wide range of human diseases. Lymphatic vascular development is initiated during embryogenesis following establishment of the major blood vessels and the onset of blood flow. Lymphatic endothelial progenitor cells arise from a combination of venous and non-venous sources to generate the initial lymphatic vascular structures in the vertebrate embryo, which are then further ramified and remodelled to elaborate an extensive lymphatic vascular network. Signalling mediated via vascular endothelial growth factor (VEGF) family members and vascular endothelial growth factor receptor (VEGFR) tyrosine kinases is crucial for development of both the blood and lymphatic vascular networks, though distinct components are utilised to different degrees in each vascular compartment. Although much is known about the regulation of VEGFA/VEGFR2 signalling in the blood vasculature, less is understood regarding the mechanisms by which VEGFC/VEGFD/VEGFR3 signalling is regulated during lymphatic vascular development. This review will focus on recent advances in our understanding of the cellular and molecular mechanisms regulating VEGFA-, VEGFC- and VEGFD-mediated signalling via VEGFRs which are important for driving the construction of lymphatic vessels during development and disease.
Assuntos
Vasos Linfáticos/metabolismo , Receptores de Fatores de Crescimento do Endotélio Vascular/metabolismo , Transdução de Sinais/fisiologia , Animais , Células Endoteliais/metabolismo , Humanos , Linfangiogênese/fisiologiaRESUMO
The lymphatic vasculature is an integral component of the immune system. Lymphatic vessels are a key highway via which immune cells are trafficked, serving not simply as a passive route of transport, but to actively shape and coordinate immune responses. Reciprocally, immune cells provide signals that impact the growth, development, and activity of the lymphatic vasculature. In addition to immune cell trafficking, lymphatic vessels are crucial for fluid homeostasis and lipid absorption. The field of lymphatic vascular research is rapidly expanding, fuelled by rapidly advancing technology that has enabled the manipulation and imaging of lymphatic vessels, together with an increasing recognition of the involvement of lymphatic vessels in a myriad of human pathologies. In this review we provide an overview of the genetic pathways and cellular processes important for development and maturation of the lymphatic vasculature, discuss recent work revealing important roles for the lymphatic vasculature in directing immune cell traffic and coordinating immune responses and highlight the involvement of lymphatic vessels in a range of pathological settings.
Assuntos
Imunidade , Linfangiogênese/fisiologia , Vasos Linfáticos/imunologia , Animais , Movimento Celular , HumanosRESUMO
Lymphatic vessels serve crucial roles in the regulation of tissue fluid homeostasis, dietary lipid absorption and immune cell trafficking. Defects in lymphatic vessel morphogenesis and function have been associated with lymphedema, obesity, hypertension and tumour metastasis. Morphogenetic events important for construction of the lymphatic vasculature during development include the specification and emergence of lymphatic endothelial progenitor cells, their differentiation and assembly into interconnected vessels and vascular remodeling, ultimately giving rise to a functional vascular network. Despite the embryonic origins of lymphatic endothelial progenitor cells being long debated, work performed over the last decade had overwhelmingly supported at least a great majority of progenitor cells arising from the venous vasculature. Here, we review the most recent advances in the field of lymphatic vessel morphogenesis, with a focus on studies that have identified novel sources of embryonic lymphatic endothelial progenitor cells, together with the cellular mechanisms by which lymphatic vessels are initially assembled.
Assuntos
Células Endoteliais/metabolismo , Células Progenitoras Endoteliais/metabolismo , Linfangiogênese/fisiologia , Vasos Linfáticos/embriologia , Animais , Células Endoteliais/citologia , Células Progenitoras Endoteliais/citologia , Humanos , Vasos Linfáticos/citologiaRESUMO
Mutations in SOX18, VEGFC and Vascular Endothelial Growth Factor 3 underlie the hereditary lymphatic disorders hypotrichosis-lymphedema-telangiectasia (HLT), Milroy-like lymphedema and Milroy disease, respectively. Genes responsible for hereditary lymphedema are key regulators of lymphatic vascular development in the embryo. To identify novel modulators of lymphangiogenesis, we used a mouse model of HLT (Ragged Opossum) and performed gene expression profiling of aberrant dermal lymphatic vessels. Expression studies and functional analysis in zebrafish and mice revealed one candidate, ArfGAP with RhoGAP domain, Ankyrin repeat and PH domain 3 (ARAP3), which is down-regulated in HLT mouse lymphatic vessels and necessary for lymphatic vascular development in mice and zebrafish. We position this known regulator of cell behaviour during migration as a mediator of the cellular response to Vegfc signalling in lymphatic endothelial cells in vitro and in vivo. Our data refine common mechanisms that are likely to contribute during both development and the pathogenesis of lymphatic vascular disorders.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Ativadoras de GTPase/genética , Regulação da Expressão Gênica , Hipotricose/genética , Linfangiogênese/genética , Linfedema/genética , Telangiectasia/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Movimento Celular/genética , Modelos Animais de Doenças , Células Endoteliais/metabolismo , Feminino , Proteínas Ativadoras de GTPase/metabolismo , Vasos Linfáticos/metabolismo , Camundongos , Camundongos Knockout , Fatores de Transcrição SOXF/genética , Fatores de Transcrição SOXF/metabolismo , Síndrome , Fator C de Crescimento do Endotélio Vascular/genética , Fator C de Crescimento do Endotélio Vascular/metabolismo , Peixe-ZebraRESUMO
Desmogleins (DSG) are a family of cadherin adhesion proteins that were first identified in desmosomes and provide cardiomyocytes and epithelial cells with the junctional stability to tolerate mechanical stress. However, one member of this family, DSG2, is emerging as a protein with additional biological functions on a broader range of cells. Here we reveal that DSG2 is expressed by non-desmosome-forming human endothelial progenitor cells as well as their mature counterparts [endothelial cells (ECs)] in human tissue from healthy individuals and cancer patients. Analysis of normal blood and bone marrow showed that DSG2 is also expressed by CD34(+)CD45(dim) hematopoietic progenitor cells. An inability to detect other desmosomal components, i.e., DSG1, DSG3 and desmocollin (DSC)2/3, on these cells supports a solitary role for DSG2 outside of desmosomes. Functionally, we show that CD34(+)CD45(dim)DSG2(+) progenitor cells are multi-potent and pro-angiogenic in vitro. Using a 'knockout-first' approach, we generated a Dsg2 loss-of-function strain of mice (Dsg2 (lo/lo)) and observed that, in response to reduced levels of Dsg2: (i) CD31(+) ECs in the pancreas are hypertrophic and exhibit altered morphology, (ii) bone marrow-derived endothelial colony formation is impaired, (iii) ex vivo vascular sprouting from aortic rings is reduced, and (iv) vessel formation in vitro and in vivo is attenuated. Finally, knockdown of DSG2 in a human bone marrow EC line reveals a reduction in an in vitro angiogenesis assay as well as relocalisation of actin and VE-cadherin away from the cell junctions, reduced cell-cell adhesion and increased invasive properties by these cells. In summary, we have identified DSG2 expression in distinct progenitor cell subpopulations and show that, independent from its classical function as a component of desmosomes, this cadherin also plays a critical role in the vasculature.
Assuntos
Desmogleína 2/metabolismo , Células Endoteliais/metabolismo , Neovascularização Fisiológica , Animais , Diferenciação Celular , Células Cultivadas , Desmogleína 2/deficiência , Desmogleína 2/genética , Células Endoteliais/citologia , Feminino , Técnicas de Silenciamento de Genes , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Células Endoteliais da Veia Umbilical Humana , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Modelos Animais , Neovascularização Fisiológica/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/genéticaRESUMO
The lymphatic vascular system develops from the pre-existing blood vasculature of the vertebrate embryo. New insights into lymphatic vascular development have recently been achieved with the use of alternative model systems, new molecular tools, novel imaging technologies and growing interest in the role of lymphatic vessels in human disorders. The signals and cellular mechanisms that facilitate the emergence of lymphatic endothelial cells from veins, guide migration through the embryonic environment, mediate interactions with neighbouring tissues and control vessel maturation are beginning to emerge. Here, we review the most recent advances in lymphatic vascular development, with a major focus on mouse and zebrafish model systems.
Assuntos
Linfangiogênese , Vasos Linfáticos/embriologia , Morfogênese , Animais , Evolução Biológica , Movimento Celular , Endotélio Vascular/citologia , Endotélio Vascular/metabolismo , Efrina-B2/genética , Efrina-B2/metabolismo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Vasos Linfáticos/citologia , Camundongos , Receptores de Fatores de Crescimento do Endotélio Vascular/genética , Receptores de Fatores de Crescimento do Endotélio Vascular/metabolismo , Transdução de Sinais , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Peixe-Zebra/embriologia , Peixe-Zebra/genética , Peixe-Zebra/metabolismoRESUMO
Lymphatic vessels are an integral component of the cardiovascular system, serving important roles in fluid homeostasis, lipid absorption, and immune cell trafficking. Defining the mechanisms by which the lymphatic vasculature is constructed and remodeled into a functional vascular network not only provides answers to fascinating biological questions, but is fundamental to understanding how lymphatic vessel growth and development goes awry in human pathologies. While long recognized as dysfunctional in lymphedema and exploited as a route of tumor metastasis, recent work has highlighted important roles for lymphatic vessels in modulating immune responses, regulating salt-sensitive hypertension and important for lung inflation at birth. Substantial progress in our understanding of the signaling pathways important for development and morphogenesis of the lymphatic vasculature has been made in recent years. Here, we review advances in our knowledge of the best characterized of these signaling pathways, that involving the vascular endothelial growth factor (VEGF) family members VEGF-C and VEGF-D, together with their receptors VEGFR2 and VEGFR3. Recent work has defined multiple levels at which signal transduction by means of this key axis is regulated; these include control of ligand processing and bioavailability, modulation of receptor activation by interacting proteins, and regulation of receptor endocytosis and trafficking.
Assuntos
Linfangiogênese/fisiologia , Vasos Linfáticos/embriologia , Transdução de Sinais/fisiologia , Células-Tronco/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Receptor 3 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Animais , Humanos , Vasos Linfáticos/citologia , Células-Tronco/citologia , Fator C de Crescimento do Endotélio Vascular/metabolismo , Fator D de Crescimento do Endotélio Vascular/metabolismoRESUMO
During embryogenesis, lymphatic endothelial progenitor cells first arise from a subset of blood vascular endothelial cells in the dorsolateral aspects of the cardinal veins. The molecular cues responsible for defining the regionalisation of such a discrete pool of progenitors remain uncharacterised. Here we identify a novel function for CYP26B1, an enzyme known to play a role in tissue morphogenesis by fine-tuning retinoic acid (RA) concentration, in regulating lymphangiogenesis. Cyp26b1-null mice, in which RA levels are elevated, exhibited an increased number of lymphatic endothelial progenitor cells in the cardinal veins, together with hyperplastic, blood filled lymph sacs and hyperplastic dermal lymphatic vessels. Conversely, mice over-expressing Cyp26b1 had hypoplastic lymph sacs and lymphatic vessels. Our data suggest that RA clearance by CYP26B1 in the vicinity of lymphatic endothelial progenitor cells is important for determining the position and size of the progenitor pool specified. Our studies identify a genetic pathway that underpins the architecture of the developing lymphatics and define CYP26B1 as a novel modulator of lymphatic vascular patterning.
Assuntos
Sistema Enzimático do Citocromo P-450/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Linfangiogênese , Sistema Linfático/embriologia , Vasos Linfáticos/metabolismo , Retinoides/metabolismo , Animais , Diferenciação Celular , Proliferação de Células , Cruzamentos Genéticos , Células Endoteliais/citologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia de Fluorescência , Fenótipo , Ácido Retinoico 4 Hidroxilase , Transdução de Sinais , Transgenes , Tretinoína/metabolismoRESUMO
Mature megakaryocytes depend on the function of Bcl-x(L), a member of the Bcl-2 family of prosurvival proteins, to proceed safely through the process of platelet shedding. Despite this, loss of Bcl-x(L) does not prevent the growth and maturation of megakaryocytes, suggesting redundancy with other prosurvival proteins. We therefore generated mice with a megakaryocyte-specific deletion of Mcl-1, which is known to be expressed in megakaryocytes. Megakaryopoiesis, platelet production, and platelet lifespan were unperturbed in Mcl-1(Pf4Δ/Pf4Δ) animals. However, treatment with ABT-737, a BH3 mimetic compound that inhibits the prosurvival proteins Bcl-2, Bcl-x(L), and Bcl-w resulted in the complete ablation of megakaryocytes and platelets. Genetic deletion of both Mcl-1 and Bcl-x(L) in megakaryocytes resulted in preweaning lethality. Megakaryopoiesis in Bcl-x(Pf4Δ/Pf4Δ) Mcl-1(Pf4Δ/Pf4Δ) embryos was severely compromised, and these animals exhibited ectopic bleeding. Our studies indicate that the combination of Bcl-x(L) and Mcl-1 is essential for the viability of the megakaryocyte lineage.
Assuntos
Megacariócitos/metabolismo , Megacariócitos/patologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Proteína bcl-X/metabolismo , Alelos , Animais , Compostos de Bifenilo/administração & dosagem , Compostos de Bifenilo/farmacologia , Contagem de Células Sanguíneas , Plaquetas/efeitos dos fármacos , Plaquetas/metabolismo , Plaquetas/patologia , Contagem de Células , Morte Celular/efeitos dos fármacos , Tamanho Celular , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Embrião de Mamíferos/efeitos dos fármacos , Embrião de Mamíferos/patologia , Feto/efeitos dos fármacos , Feto/metabolismo , Feto/patologia , Deleção de Genes , Hemorragia/patologia , Fígado/efeitos dos fármacos , Fígado/embriologia , Fígado/metabolismo , Fígado/patologia , Vasos Linfáticos/efeitos dos fármacos , Vasos Linfáticos/patologia , Megacariócitos/efeitos dos fármacos , Megacariócitos/ultraestrutura , Camundongos , Camundongos Endogâmicos C57BL , Proteína de Sequência 1 de Leucemia de Células Mieloides , Nitrofenóis/administração & dosagem , Nitrofenóis/farmacologia , Especificidade de Órgãos/efeitos dos fármacos , Piperazinas/administração & dosagem , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas c-bcl-2/deficiência , Sulfonamidas/administração & dosagem , Sulfonamidas/farmacologia , Trombopoese/efeitos dos fármacosRESUMO
Recent work has established that heterozygous germline GATA2 mutations predispose carriers to familial myelodysplastic syndrome (MDS)/acute myeloid leukemia (AML), "MonoMAC" syndrome, and DCML deficiency. Here, we describe a previously unreported MDS family carrying a missense GATA2 mutation (p.Thr354Met), one patient with MDS/AML carrying a frameshift GATA2 mutation (p.Leu332Thrfs*53), another with MDS harboring a GATA2 splice site mutation, and 3 patients exhibiting MDS or MDS/AML who have large deletions encompassing the GATA2 locus. Intriguingly, 2 MDS/AML or "MonoMAC" syndrome patients with GATA2 deletions and one with a frameshift mutation also have primary lymphedema. Primary lymphedema occurs as a result of aberrations in the development and/or function of lymphatic vessels, spurring us to investigate whether GATA2 plays a role in the lymphatic vasculature. We demonstrate here that GATA2 protein is present at high levels in lymphatic vessel valves and that GATA2 controls the expression of genes important for programming lymphatic valve development. Our data expand the phenotypes associated with germline GATA2 mutations to include predisposition to primary lymphedema and suggest that complete haploinsufficiency or loss of function of GATA2, rather than missense mutations, is the key predisposing factor for lymphedema onset. Moreover, we reveal a crucial role for GATA2 in lymphatic vascular development.
Assuntos
Fator de Transcrição GATA2/genética , Mutação em Linhagem Germinativa , Leucemia Mieloide Aguda/genética , Vasos Linfáticos/metabolismo , Linfedema/congênito , Síndromes Mielodisplásicas/genética , Adolescente , Adulto , Animais , Células Cultivadas , Criança , Feminino , Fator de Transcrição GATA2/metabolismo , Fator de Transcrição GATA2/fisiologia , Mutação em Linhagem Germinativa/fisiologia , Humanos , Recém-Nascido , Linfangiogênese/genética , Linfedema/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Monócitos/patologia , Síndrome , Adulto JovemRESUMO
Multiple organs cooperate to regulate appetite, metabolism, and glucose and fatty acid homeostasis. Here, we identified and characterized lymphatic vasculature dysfunction as a cause of adult-onset obesity. We found that functional inactivation of a single allele of the homeobox gene Prox1 led to adult-onset obesity due to abnormal lymph leakage from mispatterned and ruptured lymphatic vessels. Prox1 heterozygous mice are a new model for adult-onset obesity and lymphatic vascular disease.
Assuntos
Proteínas de Homeodomínio/genética , Metabolismo dos Lipídeos/genética , Anormalidades Linfáticas/genética , Obesidade/genética , Alelos , Animais , Modelos Animais de Doenças , Deleção de Genes , Proteínas de Homeodomínio/metabolismo , Insulina/sangue , Leptina/sangue , Lipídeos/análise , Fígado/metabolismo , Linfa/metabolismo , Anormalidades Linfáticas/complicações , Vasos Linfáticos/anormalidades , Vasos Linfáticos/fisiopatologia , Camundongos , Camundongos Knockout , Obesidade/complicações , Proteínas Supressoras de TumorRESUMO
Converging evidence indicates that extra-embryonic yolk sac is the source of both macrophages and endothelial cells in adult mouse tissues. Prevailing views are that these embryonically derived cells are maintained after birth by proliferative self-renewal in their differentiated states. Here we identify clonogenic endothelial-macrophage (EndoMac) progenitor cells in the adventitia of embryonic and postnatal mouse aorta, that are independent of Flt3-mediated bone marrow hematopoiesis and derive from an early embryonic CX3CR1+ and CSF1R+ source. These bipotent progenitors are proliferative and vasculogenic, contributing to adventitial neovascularization and formation of perfused blood vessels after transfer into ischemic tissue. We establish a regulatory role for angiotensin II, which enhances their clonogenic and differentiation properties and rapidly stimulates their proliferative expansion in vivo. Our findings demonstrate that embryonically derived EndoMac progenitors participate in local vasculogenic responses in the aortic wall by contributing to the expansion of endothelial cells and macrophages postnatally.