Formation of the definitive endoderm in mouse is a Smad2-dependent process

Development ◽  
2000 ◽  
Vol 127 (14) ◽  
pp. 3079-3090 ◽  
Author(s):  
K.D. Tremblay ◽  
P.A. Hoodless ◽  
E.K. Bikoff ◽  
E.J. Robertson
Keyword(s):  
Cell Fate ◽  
Es Cells ◽  
Primitive Streak ◽  
Definitive Endoderm ◽  
Effector Proteins ◽  
The Body ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Primary Defect ◽  
Surface Receptor

TGFbeta growth factors specify cell fate and establish the body plan during early vertebrate development. Diverse cellular responses are elicited via interactions with specific cell surface receptor kinases that in turn activate Smad effector proteins. Smad2-dependent signals arising in the extraembryonic tissues of early mouse embryos serve to restrict the site of primitive streak formation and establish anteroposterior identity in the epiblast. Here we have generated chimeric embryos using lacZ-marked Smad2-deficient ES cells. Smad2 mutant cells extensively colonize ectodermal and mesodermal populations without disturbing normal development, but are not recruited into the definitive endoderm lineage during gastrulation. These experiments provide the first evidence that TGFbeta signaling pathways are required for specification of the definitive endoderm lineage in mammals and identify Smad2 as a key mediator that directs epiblast derivatives towards an endodermal as opposed to a mesodermal fate. In largely Smad2-deficient chimeras, asymmetric nodal gene expression is maintained and expression of pitx2, a nodal target, is also unaffected. These results strongly suggest that other Smad(s) act downstream of Nodal signals in mesodermal populations. We found Smad2 and Smad3 transcripts both broadly expressed in derivatives of the epiblast. However, Smad2 and not Smad3 mRNA is expressed in the visceral endoderm, potentially explaining why the primary defect in Smad2 mutant embryos originates in this cell population.

scholarly journals Determination of the molecular mass of apolipoprotein B-100 A chemical approach

1986 ◽  
Vol 239 (3) ◽  
pp. 777-780 ◽  
Author(s):  
C Y Yang ◽  
F S Lee ◽  
L Chan ◽  
D A Sparrow ◽  
J T Sparrow ◽  
...  
Keyword(s):  
Molecular Mass ◽  
Apolipoprotein B ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Apo B ◽  
Chemical Approach ◽  
Surface Receptor ◽  
Cnbr Cleavage ◽  
Specific Cell Surface

Apolipoprotein B-100 (apo B-100) is the protein ligand in low-density lipoproteins that binds to a specific cell-surface receptor. Its molecular mass has been a subject of controversy. We have determined the molecular mass of the protein by a chemical approach. After complete CNBr cleavage, the C-terminal fragment of apo B-100 was purified by reverse-phase h.p.l.c. Amino acid N- and C-terminal analyses confirm that this peptide represents the C-terminal peptide as deduced from the DNA sequence of a human apo B-100 cDNA clone. A chemically synthesized peptide was used to determine the recovery of the peptide (74.72%). On the basis of these data, the molecular mass of apo B-100 was determined to be 496.82 +/- 24.84 kDa.

Increased hemangioblast commitment, not vascular disorganization, is the primary defect in flt-1 knock-out mice

Development ◽  
1999 ◽  
Vol 126 (13) ◽  
pp. 3015-3025 ◽  
Author(s):  
G.H. Fong ◽  
L. Zhang ◽  
D.M. Bryce ◽  
J. Peng
Keyword(s):  
Endothelial Cells ◽  
Population Density ◽  
Cell Fate ◽  
Vascular System ◽  
Primitive Streak ◽  
Cellular Level ◽  
Wild Type ◽  
Primary Defect ◽  
Knock Out ◽  
Vascular Channels

We previously demonstrated the essential role of the flt-1 gene in regulating the development of the cardiovascular system. While the inactivation of the flt-1 gene leads to a very severe disorganization of the vascular system, the primary defect at the cellular level was unknown. Here we report a surprising finding that it is an increase in the number of endothelial progenitors that leads to the vascular disorganization in flt-1(−/−) mice. At the early primitive streak stage (prior to the formation of blood islands), hemangioblasts are formed much more abundantly in flt-1(−/−) embryos. This increase is primarily due to an alteration in cell fate determination among mesenchymal cells, rather than to increased proliferation, migration or reduced apoptosis of flt-1(−/−) hemangioblasts. We further show that the increased population density of hemangioblasts is responsible for the observed vascular disorganization, based on the following observations: (1) both flt-1(−/−) and flt-1(+/+) endothelial cells formed normal vascular channels in chimaeric embryos; (2) wild-type endothelial cells formed abnormal vascular channels when their population density was significantly increased; and (3) in the absence of wild-type endothelial cells, flt-1(−/−) endothelial cells alone could form normal vascular channels when sufficiently diluted in a developing embryo. These results define the primary defect in flt-1(−/−) embryos at the cellular level and demonstrate the importance of population density of progenitor cells in pattern formation.

Neurotransmitter Control of Secretion

1987 ◽  
Vol 66 (1_suppl) ◽  
pp. 628-632 ◽  
Author(s):  
B. J. Baum
Keyword(s):  
Plasma Membrane ◽  
Salivary Gland ◽  
Salivary Secretion ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Neural Signal ◽  
N Protein ◽  
Transduction Mechanisms ◽  
Surface Receptor ◽  
Specific Cell Surface

It is very well established that the principal control of salivary secretion is derived from autonomic innervation. Transmission of a neural signal to a salivary gland acinar cell occurs chemically via neurotransmitters, the first messengers of a secretory response. Neurotransmitters bind to specific cell surface receptor proteins, an event which activates precise transduction mechanisms which then transfer the neural signal to the inside of the cell. There are two major transduction mechanisms operative in salivary gland acinar cells. One involves the generation of cAMP, the other involves the breakdown of plasma membrane polyphosphoinositides. For both mechanisms, the appropriate stimulated receptor activates a second plasma membrane protein, termed an N (or G) protein. The N protein requires GTP to activate an enzyme (adenylate cyclase or phospholipase C), which then catalyzes the formation of a second messenger (cAMP and inositol trisphosphatel diacylglyeerol, respectively). This action provides the intracellular signal for secretory events (protein, fluid, electrolyte secretion) to begin.

scholarly journals MECHANISM OF ACTION OF MIGRATION INHIBITORY FACTOR (MIF)

1972 ◽  
Vol 136 (3) ◽  
pp. 589-603 ◽  
Author(s):  
Richard W. Leu ◽  
A. L. W. F. Eddleston ◽  
John W. Hadden ◽  
Robert A. Good
Keyword(s):  
Alveolar Macrophage ◽  
Peritoneal Macrophage ◽  
Migration Inhibitory Factor ◽  
Immune Modulation ◽  
Peritoneal Macrophages ◽  
Cell Number ◽  
Inhibitory Factor ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Surface Receptor

The initial interaction between migration inhibitory factor (MIF) and the guinea pig alveolar and peritoneal macrophage was studied. MIF-containing supernatants were generated from sensitized lymph node lymphocytes obtained from guinea pigs immunized with bovine gamma globulin in complete Freund's adjuvant. MIF-containing supernatants were markedly inhibitory for the migration of the peritoneal macrophage but had no effect on the alveolar macrophage. A linear relationship was observed between per cent inhibition of migration and serial twofold dilution of supernatant. Reexpressed in arbitrary MIF units, this relationship reflects a dose-response relationship with saturation characteristics. Pulse exposure of peritoneal macrophages to MIF resulted in adsorption of MIF onto both viable and nonviable cells with corresponding depletion of supernatant MIF. The alveolar macrophage did not adsorb MIF. Pulse adsorption of MIF onto the peritoneal macrophage is dependent on time, temperature, and cell number. Pretreatment of the cells with proteolytic enzyme prevents the adsorption of MIF while leaving migration unaffected. These observations support the existence of a specific cell surface receptor for MIF. The existence of such a receptor provides selectivity of immune modulation of macrophage populations by lymphocytes in delayed hypersensitivity reactions.

Sialylation of the Sialic Acid Binding Lectin Sialoadhesin Regulates Its Ability to Mediate Cell Adhesion

Blood ◽  
1999 ◽  
Vol 93 (4) ◽  
pp. 1245-1252 ◽  
Author(s):  
Yvonne C. Barnes ◽  
Tim P. Skelton ◽  
Ivan Stamenkovic ◽  
Dennis C. Sgroi
Keyword(s):  
Sialic Acid ◽  
Inhibitory Effect ◽  
Binding Activity ◽  
Cell Surface Receptor ◽  
Common Mechanism ◽  
Specific Cell ◽  
Sialic Acid Binding ◽  
Surface Receptor ◽  
Mediate Cell

The macrophage-specific cell surface receptor sialoadhesin, which is a member of the newly recognized family of sialic acid binding lectins called siglecs, binds glycoprotein and glycolipid ligands containing a2-3–linked sialic acid on the surface of several leukocyte subsets. Recently, the sialic acid binding activity of the siglec CD22 has been demonstrated to be regulated by sialylation of the CD22 receptor molecule. In the present work, we show that desialylation of in vivo macrophage sialylconjugates enhances sialoadhesin-mediated lectin activity. Herein, we show that receptor sialylation of soluble sialoadhesin inhibits its binding to Jurkat cell ligands, and that charge-dependent repulsion alone cannot explain this inhibition. Furthermore, we show that the inhibitory effect of sialic acid is partially dependent on the presence of an intact exocyclic side chain. These results, in conjunction with previous findings, suggest that sialylation of siglecs by specific glycosyltransferases may be a common mechanism by which siglec-mediated adhesion is regulated.

Regulation of the Urokinase Receptor by Its Plasminogen Activator

1991 ◽  
Vol 66 (06) ◽  
pp. 678-683 ◽  
Author(s):  
W Hollas ◽  
D Boyd
Keyword(s):  
Molecular Weight ◽  
Plasminogen Activator ◽  
Specific Binding ◽  
Cell Surface Receptor ◽  
Specific Cell ◽  
Acid Pretreatment ◽  
Ample Evidence ◽  
Surface Receptor ◽  
A Chain ◽  
The Uk

SummaryThere is now ample evidence that the proteolytic action of urokinase (UK) is potentiated by a specific cell surface receptor. The present study was undertaken to assess the role of UK as a modulator of its receptor. GEO colonic cells, which secrete relatively low levels of UK (≃0.1 nM/72 h per 106 cells) and display approximately 104 receptors per cell, 10% of which are "tagged" with the endogenous plasminogen activator (PA), was selected for the study. A 90% reduction in the specific binding of radioactive DFP-UK was observed for cells cultivated in the presence of two-chain (TC) UK (M r 55,000). This only partly reflected occupation of the receptors with UK supplied in the culture medium, since the specific binding of the radioligand was still reduced by 60% after an acid pretreatment, which dissociates receptor-bound UK. The reduction in radioactive DFP-UK binding to cells treated with high molecular weight UK, either in the single or two-chain form, was both concentration and time dependent. Maximum reductions (70%) were achieved by treatment of the cells for 24 h with 1 nM of the plasminogen activator. In contrast, low molecular weight UK, which lacks part of the UK A chain, had no effect on ligand binding. Attenuation of radioactive DFP-UK binding to UK treated GEO cells was a consequence of a 60% reduction in the number of binding sites. Treatment of GEO cells with an antibody, which blocks the binding of endogenous UK to its receptor, augmented radioactive DFP-UK binding by two-fold. These data indicate that for one colonic cell line, at least, UK down-regulates its own binding site subsequent to it being bound to the receptor.

scholarly journals Growth response of acute myeloblastic leukemia cells to recombinant human thrombopoietin

Blood ◽  
1995 ◽  
Vol 86 (2) ◽  
pp. 703-709 ◽  
Author(s):  
I Matsumura ◽  
Y Kanakura ◽  
T Kato ◽  
H Ikeda ◽  
J Ishikawa ◽  
...  
Keyword(s):  
Proliferative Response ◽  
Acute Myeloblastic Leukemia ◽  
Cell Surface Receptor ◽  
Leukemia Cells ◽  
Specific Cell ◽  
Hematopoietic Growth Factors ◽  
Abnormal Growth ◽  
Surface Receptor ◽  
Macrophage Colony

Thrombopoietin (TPO) is a newly identified hematopoietic growth factor that stimulates both megakaryopoiesis and thrombopoiesis through its interaction with a specific cell surface receptor encoded by the c-mpl proto-oncogene. In an effort to investigate the effect of TPO on human myeloid leukemia cells, the expression of c-mpl and the proliferative response to recombinant human (rh) TPO were investigated in a series of patients with acute myeloblastic leukemia (AML). Of 50 cases of AML, the c-mpl mRNA was detectable by means of Northern blot analysis in 26 cases, and the in vitro treatment with rhTPO led to proliferation of AML cells in 22 cases. The c-mpl expression and proliferative response to rhTPO was observed in all subtypes of AML and did not correlate with French-American-British classification, whereas all cases of M7-type AML cells expressed c-mpl and proliferated in response to rhTPO. Furthermore, rhTPO-induced proliferation of AML cells was augmented with the addition of interleukin-3 (IL-3), IL-6, stem cell factor, or granulocyte-macrophage colony-stimulating factor. These results suggested that c-mpl may be functional in terms of supporting proliferation of various types of AML cells and that TPO may contribute, at least in part, to abnormal growth of the cells, especially in combination with other hematopoietic growth factors.

Expression pattern of the Brachyury gene in whole-mount TWis/TWis mutant embryos

Development ◽  
1991 ◽  
Vol 113 (3) ◽  
pp. 913-917 ◽  
Author(s):  
B.G. Herrmann
Keyword(s):  
Gene Product ◽  
Gene Dosage ◽  
Primitive Streak ◽  
The Body ◽  
Primary Defect ◽  
Whole Mount ◽  
Mesoderm Formation ◽  
Axis Elongation ◽  
Severe Disturbance ◽  
Axial Development

The murine Brachyury (T) gene is required in mesoderm formation. Mutants carrying different T alleles show a graded severity of defects correlated with gene dosage along the body axis. The phenotypes range from shortening of the tail to the malformation of sacral vertebrae in heterozygotes, and to disruption of trunk development and embryonic death in homozygotes. Defects include a severe disturbance of the primitive streak, an early cessation of mesoderm formation and absence of the allantois and notochord, the latter resulting in an abnormality of the neural tube and somites. The T gene is expressed in nascent mesoderm and in the notochord of wild-type embryos. Here the expression of T in whole-mount mutant embryos homozygous for the T allele TWis is described. The TWis gene product is altered, but the TWis/TWis phenotype is very similar to that of T/T embryos which lack T. In early TWis/TWis embryos T expression is normal, but ceases prematurely during early organogenesis coincident with a cessation of mesoderm formation. The archenteron/node region is disrupted and the extension of the notochord precursor comes to a halt, followed by a decrease and finally a complete loss of T gene expression in the primitive streak and the head process/notochord precursor. It appears that the primary defect of the mutant embryo is the disruption of the notochord precursor in the node region which is required for axis elongation. Thus the T gene product is directly or indirectly involved in the organization of axial development.

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