SCL Expression in the Mouse Embryo Detected With a Targeted lacZ Reporter Gene Demonstrates Its Localization to Hematopoietic, Vascular, and Neural Tissues

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3754-3763 ◽  
Author(s):  
Andrew G. Elefanty ◽  
C. Glenn Begley ◽  
Lynne Hartley ◽  
Bette Papaevangeliou ◽  
Lorraine Robb
Keyword(s):  
Mouse Embryo ◽  
Fetal Liver ◽  
Cell Formation ◽  
Developmental Potential ◽  
Vascular Plexus ◽  
Helix Loop Helix ◽  
Liver Culture ◽  
The Central Nervous System ◽  
Vascular Endothelia ◽  
Low Levels

Abstract The helix-loop-helix transcription factor SCL (TAL1) is indispensable for blood cell formation in the mouse embryo. We have explored the localization and developmental potential of cells fated to express SCL during murine development using SCL-lacZmutant mice in which the Escherichia coli lacZreporter gene was ‘knocked in’ to the SCL locus. In addition to the hematopoietic defect associated with SCL deficiency, the yolk sac blood vessels in SCLlacZ/lacZ embryos formed an abnormal primary vascular plexus, which failed to undergo subsequent remodeling and formation of large branching vessels. Intraembryonic vasculogenesis in precirculationSCLlacZ/lacZ embryos appeared normal but, in embryos older than embryonic day (E) 8.5 to E9, absolute anemia leading to severe hypoxia precluded an accurate assessment of further vascular development. In heterozygous SCLlacZ/w embryos, lacZ was expressed in the central nervous system, vascular endothelia, and primitive and definitive hematopoietic cells in the blood, aortic wall, and fetal liver. Culture of fetal liver cells sorted for high and low levels of β galactosidase activity fromSCLlacZ/w heterozygous embryos indicated that there was a correlation between the level of SCL expression and the frequency of hematopoietic progenitor cells.

SCL Expression in the Mouse Embryo Detected With a Targeted lacZ Reporter Gene Demonstrates Its Localization to Hematopoietic, Vascular, and Neural Tissues

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3754-3763 ◽  
Author(s):  
Andrew G. Elefanty ◽  
C. Glenn Begley ◽  
Lynne Hartley ◽  
Bette Papaevangeliou ◽  
Lorraine Robb
Keyword(s):  
Mouse Embryo ◽  
Fetal Liver ◽  
Cell Formation ◽  
Developmental Potential ◽  
Vascular Plexus ◽  
Helix Loop Helix ◽  
Liver Culture ◽  
The Central Nervous System ◽  
Vascular Endothelia ◽  
Low Levels

The helix-loop-helix transcription factor SCL (TAL1) is indispensable for blood cell formation in the mouse embryo. We have explored the localization and developmental potential of cells fated to express SCL during murine development using SCL-lacZmutant mice in which the Escherichia coli lacZreporter gene was ‘knocked in’ to the SCL locus. In addition to the hematopoietic defect associated with SCL deficiency, the yolk sac blood vessels in SCLlacZ/lacZ embryos formed an abnormal primary vascular plexus, which failed to undergo subsequent remodeling and formation of large branching vessels. Intraembryonic vasculogenesis in precirculationSCLlacZ/lacZ embryos appeared normal but, in embryos older than embryonic day (E) 8.5 to E9, absolute anemia leading to severe hypoxia precluded an accurate assessment of further vascular development. In heterozygous SCLlacZ/w embryos, lacZ was expressed in the central nervous system, vascular endothelia, and primitive and definitive hematopoietic cells in the blood, aortic wall, and fetal liver. Culture of fetal liver cells sorted for high and low levels of β galactosidase activity fromSCLlacZ/w heterozygous embryos indicated that there was a correlation between the level of SCL expression and the frequency of hematopoietic progenitor cells.

scholarly journals The SCL/TAL-1 gene is expressed in progenitors of both the hematopoietic and vascular systems during embryogenesis

Blood ◽  
1994 ◽  
Vol 83 (5) ◽  
pp. 1200-1208 ◽  
Author(s):  
AR Kallianpur ◽  
JE Jordan ◽  
SJ Brandt
Keyword(s):  
T Cell ◽  
Neural Development ◽  
Fetal Liver ◽  
Chromosomal Rearrangements ◽  
Chromosomal Translocation ◽  
Cell Types ◽  
Hematopoietic Differentiation ◽  
Helix Loop Helix ◽  
Adult Mice ◽  
Rare Cells

Activation of the SCL (or TAL-1) gene as a result of chromosomal translocation or deletion is a frequent molecular lesion in acute T- cell leukemia. By virtue of its membership in the basic helix-loop- helix family of transcription factors, the SCL gene is a candidate to regulate events in hematopoietic differentiation. We have used polyclonal antibody raised against a bacterial expressed malE-SCL fusion protein to characterize SCL protein expression in postimplantation embryos and in neonatal and adult mice. SCL protein was detected at day 7.5 post coitum at both embryonic and extraembryonic sites, approximately 24 hours before the formation of recognizable hematopoietic elements. Expression then localized to blood islands of the yolk sac followed by localization to fetal liver and spleen, paralleling the hematopoietic activity of these tissues during development. SCL protein was detected in erythroblasts in fetal and adult spleen, myeloid cells and megakaryocytes in spleen and bone marrow, mast cells in skin, and in rare cells in fetal and adult thymus. In addition, SCL protein was noted in endothelial progenitors in blood islands and in endothelial cells and angioblasts in a number of organs at times coincident with their vascularization. SCL expression was also observed in other nonhematopoietic cell types in the developing skeletal and nervous systems. These results show that SCL expression is one of the earliest markers of mammalian hematopoietic development and are compatible with a role for this transcription factor in terminal differentiation of the erythroid and megakaryocytic lineages. SCL expression by cells in the thymus suggests that the gene may be active at some stage of T-cell differentiation and may be relevant to its involvement by chromosomal rearrangements in T- lymphoid leukemias. Finally, expression of the gene in developing brain, cartilage, and vascular endothelium indicates SCL may have actions in neural development, osteogenesis, and vasculogenesis, as well as in hematopoietic differentiation.

scholarly journals Macrophages Enforce the Blood Nerve Barrier

2019 ◽  
Author(s):  
Liza Malong ◽  
Ilaria Napoli ◽  
Ian J White ◽  
Salome Stierli ◽  
Alessandro Bossio ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Barrier Function ◽  
Cellular Composition ◽  
Complete Coverage ◽  
Therapeutic Delivery ◽  
The Central Nervous System ◽  
Low Levels ◽  
Cellular Components ◽  
Distinct Role

The specialised blood barriers of the nervous system are important for protecting the neural environment but can hinder therapeutic accessibility1,2. Studies in the central nervous system (CNS) have shown the importance of the cellular components of the neuro-vascular unit for blood-brain barrier (BBB) function. Whilst the endothelial cells (ECs) confer barrier function with specialised tight junctions (TJs) and low levels of transcytosis, pericytes and astrocytes provide complete coverage of the ECs and both deliver essential signals for the development and maintenance of the BBB3–9. In contrast, the blood-nerve barrier (BNB) of the peripheral nervous system (PNS) remains poorly defined10. Here, we show that the vascular unit in the PNS has a distinct cellular composition with only partial coverage of the BNB-forming ECs. Using a mouse model, in which barrier function can be controlled11, we show the BNB, while less tight than the BBB, is maintained by low levels of transcytosis and the TJs of the ECs, with opening of the barrier associated with increased transcytosis. Importantly, we find that while ECs of the PNS have higher transcytosis rates than those of the CNS, the barrier is reinforced by resident macrophages that specifically engulf leaked material. This identifies a distinct role for macrophages as an important component of the BNB acting to protect the PNS environment with implications for improving therapeutic delivery to this tissue.

The differentiation in vitro of the neural crest cells of the mouse embryo

Development ◽  
1984 ◽  
Vol 84 (1) ◽  
pp. 49-62
Author(s):  
Kazuo Ito ◽  
Takuji Takeuchi
Keyword(s):  
Neural Crest ◽  
Mouse Embryo ◽  
Neural Crest Cells ◽  
Culture Method ◽  
Gene Control ◽  
Developmental Potential ◽  
Neural Tubes ◽  
Epithelial Sheet ◽  
Culture Phase

A culture method for neural crest cells of mouse embryo is described. Trunk neural tubes were dissected from 9-day mouse embryos and explanted in culture dishes. The developmental potential of mouse neural crest in vitro was shown to be essentially similar to that of avian neural crest. In the mouse, however, melanocytes always appeared in association with the epithelial sheet close to the explant. Neural crest cells surrounding the epithelial sheet, which probably migrated from the neural tubes in the early culture phase, never differentiated into melanocytes. The bimodal behaviour of mouse crest cells seems to be due to the heterogenous potency of the crest cells and the interaction of these cells with the surrounding microenvironment. This culture system is well suited for various experiments including the analysis of gene control on the differentiation of neural crest cells.

scholarly journals FLK-2/FLT-3 ligand regulates the growth of early myeloid progenitors isolated from human fetal liver

Blood ◽  
1995 ◽  
Vol 85 (4) ◽  
pp. 963-972 ◽  
Author(s):  
MO Muench ◽  
MG Roncarolo ◽  
S Menon ◽  
Y Xu ◽  
R Kastelein ◽  
...  
Keyword(s):  
Fetal Liver ◽  
Culture Conditions ◽  
Proliferative Potential ◽  
Growth And Survival ◽  
Human Fetal Liver ◽  
Gm Csf ◽  
Clonal Cultures ◽  
Macrophage Colony Stimulating Factor ◽  
Low Levels ◽  
Macrophage Colony

The effects of the recently identified FLK-2/FLT-3 ligand (FL) on the growth of purified human fetal liver progenitors were investigated under serum-deprived culture conditions. FL alone was found to stimulate modest proliferation in short-term cultures of CD34++ CD38+ lineage (Lin)- light-density fetal liver (LDFL) cells and the more primitive CD34++ CD38- Lin- LDFL cells. However, the low levels of growth induced by FL were insufficient for colony formation in clonal cultures. Synergism between FL and either granulocyte-macrophage colony- stimulating factor (GM-CSF), interleukin-3 (IL-3) or KIT ligand (KL) was observed in promoting the growth of high-proliferative potential (HPP) colony-forming cells (CF) and/or low-proliferative potential (LPP)-CFC in cultures of CD34++ CD38+ Lin- and CD34++ CD38- Lin- LDFL- cells. FL, alone or in combination with other cytokines, was not found to affect the growth of CD34+ Lin- LDFL cells, the most mature subpopulation of fetal liver progenitors investigated. The growth of the most primitive subset of progenitors studied, CD34++ CD38- Lin- LDFL cells, required the interactions of at least two cytokines, because only very low levels of growth were observed in response to either FL, GM-CSF, IL-3 or KL alone. However, the results of delayed cytokine-addition experiments suggested that individually these cytokines did promote the survival of this early population of progenitors. Although two-factor combinations of FL, KL, and GM-CSF were observed to promote the growth of early progenitors in a synergistic manner, neither of these factors was found to make fetal liver progenitors more responsive to suboptimal concentrations of a second cytokine. Only myeloid cells were recovered from liquid cultures of CD34++ CD38- Lin- LDFL cells grown in the presence of combinations of FL, KL, and GM-CSF. These results indicate that FL is part of a network of growth factors that regulate the growth and survival of early hematopoietic progenitors.

scholarly journals Expansion of hematopoietic stem cells in the developing liver of a mouse embryo

Blood ◽  
2000 ◽  
Vol 95 (7) ◽  
pp. 2284-2288 ◽  
Author(s):  
Hideo Ema ◽  
Hiromitsu Nakauchi
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Mouse Embryo ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Cell Number ◽  
Liver Cells ◽  
Single Wave ◽  
Hematopoietic Stem ◽  
Fetal Liver Cells

Abstract The activity of hematopoietic stem cells in the developing liver of a C57BL/6 mouse embryo was quantified by a competitive repopulation assay. Different doses of fetal liver cells at days 11 to 18 of gestation were transplanted into irradiated mice together with 2 × 105 adult bone marrow cells. A long-term repopulation in myeloid-, B-cell, and T-cell lineage by fetal liver cells was evaluated at 20 weeks after transplantation. At day 12 of gestation multilineage repopulating activity was first detected in the liver as 50 repopulating units (RU) per liver. The number of RU per liver increased 10-fold and 33-fold by day 14 and day 16 of gestation, and decreased thereafter, suggesting a single wave of stem cell development in the fetal liver. A limiting dilution analysis revealed that the frequency of competitive repopulating units (CRU) in fetal liver cells at day 12 of gestation was similar to that at day 16 of gestation. Because of an increase of total fetal liver cell number, the absolute number of CRU per liver from days 12 to 16 of gestation increased 38-fold. Hence, the mean activity of stem cells (MAS) that is given by RU per CRU remained constant from days 12 to 16 of gestation. From these data we conclude that hematopoietic stem cells expand in the fetal liver maintaining their level of repopulating potential.

scholarly journals Developmental trajectory of prehematopoietic stem cell formation from endothelium

Blood ◽  
2020 ◽  
Vol 136 (7) ◽  
pp. 845-856 ◽  
Author(s):  
Qin Zhu ◽  
Peng Gao ◽  
Joanna Tober ◽  
Laura Bennett ◽  
Changya Chen ◽  
...  
Keyword(s):  
Single Cell ◽  
Fetal Liver ◽  
Developmental Trajectories ◽  
Cell Formation ◽  
Intermediate Stage ◽  
Chromatin Accessibility ◽  
Small Population ◽  
Developmental Trajectory ◽  
Mammalian Embryo ◽  
Hematopoietic Stem

Abstract Hematopoietic stem and progenitor cells (HSPCs) in the bone marrow are derived from a small population of hemogenic endothelial (HE) cells located in the major arteries of the mammalian embryo. HE cells undergo an endothelial to hematopoietic cell transition, giving rise to HSPCs that accumulate in intra-arterial clusters (IAC) before colonizing the fetal liver. To examine the cell and molecular transitions between endothelial (E), HE, and IAC cells, and the heterogeneity of HSPCs within IACs, we profiled ∼40 000 cells from the caudal arteries (dorsal aorta, umbilical, vitelline) of 9.5 days post coitus (dpc) to 11.5 dpc mouse embryos by single-cell RNA sequencing and single-cell assay for transposase-accessible chromatin sequencing. We identified a continuous developmental trajectory from E to HE to IAC cells, with identifiable intermediate stages. The intermediate stage most proximal to HE, which we term pre-HE, is characterized by increased accessibility of chromatin enriched for SOX, FOX, GATA, and SMAD motifs. A developmental bottleneck separates pre-HE from HE, with RUNX1 dosage regulating the efficiency of the pre-HE to HE transition. A distal candidate Runx1 enhancer exhibits high chromatin accessibility specifically in pre-HE cells at the bottleneck, but loses accessibility thereafter. Distinct developmental trajectories within IAC cells result in 2 populations of CD45+ HSPCs; an initial wave of lymphomyeloid-biased progenitors, followed by precursors of hematopoietic stem cells (pre-HSCs). This multiomics single-cell atlas significantly expands our understanding of pre-HSC ontogeny.

Expression of CD41 marks the initiation of definitive hematopoiesis in the mouse embryo

Blood ◽  
2003 ◽  
Vol 101 (2) ◽  
pp. 508-516 ◽  
Author(s):  
Hanna K. A. Mikkola ◽  
Yuko Fujiwara ◽  
Thorsten M. Schlaeger ◽  
David Traver ◽  
Stuart H. Orkin
Keyword(s):  
Endothelial Cells ◽  
Mouse Embryo ◽  
Fetal Liver ◽  
Stem Cell Differentiation ◽  
Yolk Sac ◽  
Embryoid Bodies ◽  
Embryonic Stem Cell Differentiation ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Stem ◽  
Definitive Hematopoiesis

Murine hematopoietic stem cells (HSCs) originate from mesoderm in a process that requires the transcription factor SCL/Tal1. To define steps in the commitment to blood cell fate, we compared wild-type and SCL−/− embryonic stem cell differentiation in vitro and identified CD41 (GpIIb) as the earliest surface marker missing from SCL−/− embryoid bodies (EBs). Culture of fluorescence-activated cell sorter (FACS) purified cells from EBs showed that definitive hematopoietic progenitors were highly enriched in the CD41+ fraction, whereas endothelial cells developed from CD41− cells. In the mouse embryo, expression of CD41 was detected in yolk sac blood islands and in fetal liver. In yolk sac and EBs, the panhematopoietic marker CD45 appeared in a subpopulation of CD41+ cells. However, multilineage hematopoietic colonies developed not only from CD45+CD41+ cells but also from CD45−CD41+ cells, suggesting that CD41 rather than CD45 marks the definitive culture colony-forming unit (CFU-C) at the embryonic stage. In contrast, fetal liver CFU-C was CD45+, and only a subfraction expressed CD41, demonstrating down-regulation of CD41 by the fetal liver stage. In yolk sac and EBs, CD41 was coexpressed with embryonic HSC markers c-kit and CD34. Sorting for CD41 and c-kit expression resulted in enrichment of definitive hematopoietic progenitors. Furthermore, the CD41+c-kit+ population was missing from runx1/AML1−/− EBs that lack definitive hematopoiesis. These results suggest that the expression of CD41, a candidate target gene of SCL/Tal1, and c-kit define the divergence of definitive hematopoiesis from endothelial cells during development. Although CD41 is commonly referred to as megakaryocyte–platelet integrin in adult hematopoiesis, these results implicate a wider role for CD41 during murine ontogeny.

scholarly journals Developmental potential and behavior of tetraploid cells in the mouse embryo

2005 ◽  
Vol 288 (1) ◽  
pp. 150-159 ◽  
Author(s):  
Guy S. Eakin ◽  
Anna-Katerina Hadjantonakis ◽  
Virginia E. Papaioannou ◽  
Richard R. Behringer
Keyword(s):  
Mouse Embryo ◽  
Developmental Potential ◽  
And Behavior

scholarly journals Mef2C is a lineage-restricted target of Scl/Tal1 and regulates megakaryopoiesis and B-cell homeostasis

Blood ◽  
2009 ◽  
Vol 113 (15) ◽  
pp. 3461-3471 ◽  
Author(s):  
Christos Gekas ◽  
Katrin E. Rhodes ◽  
Laurraine M. Gereige ◽  
Hildur Helgadottir ◽  
Roberto Ferrari ◽  
...  
Keyword(s):  
Transcription Factor ◽  
B Cell ◽  
Fetal Liver ◽  
Premature Aging ◽  
Functional Requirements ◽  
Helix Loop Helix ◽  
B Cell Homeostasis ◽  
B Lymphoid ◽  
Deficient Mice

Abstract The basic helix-loop-helix transcription factor stem cell leukemia gene (Scl) is a master regulator for hematopoiesis essential for hematopoietic specification and proper differentiation of the erythroid and megakaryocyte lineages. However, the critical downstream targets of Scl remain undefined. Here, we identified a novel Scl target gene, transcription factor myocyte enhancer factor 2 C (Mef2C) from Sclfl/fl fetal liver progenitor cell lines. Analysis of Mef2C−/− embryos showed that Mef2C, in contrast to Scl, is not essential for specification into primitive or definitive hematopoietic lineages. However, adult VavCre+Mef2Cfl/fl mice exhibited platelet defects similar to those observed in Scl-deficient mice. The platelet counts were reduced, whereas platelet size was increased and the platelet shape and granularity were altered. Furthermore, megakaryopoiesis was severely impaired in vitro. Chromatin immunoprecipitation microarray hybridization analysis revealed that Mef2C is directly regulated by Scl in megakaryocytic cells, but not in erythroid cells. In addition, an Scl-independent requirement for Mef2C in B-lymphoid homeostasis was observed in Mef2C-deficient mice, characterized as severe age-dependent reduction of specific B-cell progenitor populations reminiscent of premature aging. In summary, this work identifies Mef2C as an integral member of hematopoietic transcription factors with distinct upstream regulatory mechanisms and functional requirements in megakaryocyte and B-lymphoid lineages.

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