De novo induction of the organizer and formation of the primitive streak in an experimental model of notochord reconstitution in avian embryos

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 201-213 ◽  
Author(s):  
S. Yuan ◽  
G.C. Schoenwolf
Keyword(s):  
Cell Fate ◽  
De Novo ◽  
Primitive Streak ◽  
Model System ◽  
Floor Plate ◽  
Avian Embryos ◽  
New Information ◽  
Derivatives Of ◽  
Novel Model ◽  
Neurula Stage

We have developed a model system for analyzing reconstitution of the notochord using cultured blastoderm isolates lacking Hensen's node and the primitive streak. Despite lacking normal notochordal precursor cells, the notochord still forms in these isolates during the 36 hours in culture. Reconstitution of the notochord involves an inducer, which acts upon a responder, thereby inducing a reconstituted notochord. To better understand the mechanism of notochord reconstitution, we asked whether formation of the notochord in the model system was preceded by reconstitution of Hensen's node, the organizer of the avian neuraxis. Our results show not only that a functional organizer is reconstituted, but that this organizer is induced from the responder. First, fate mapping reveals that the responder forms a density, morphologically similar to Hensen's node, during the first 10–12 hours in culture, and that this density expresses typical markers of Hensen's node. Second, the density, when fate mapped or when labeled and transplanted in place of Hensen's node, forms typical derivatives of Hensen's node such as endoderm, notochord and the floor plate of the neural tube. Third, the density, when transplanted to an ectopic site, induces a secondary neuraxis, identical to that induced by Hensen's node. And fourth, the density acts as a suppressor of notochord reconstitution, as does Hensen's node, when transplanted to other blastoderm isolates. Our results also reveal that the medial edge of the isolate forms a reconstituted primitive streak, which gives rise to the normal derivatives of the definitive primitive streak along its rostrocaudal extent and which expresses typical streak markers. Finally, our results demonstrate that the notochordal inducer also induces the reconstituted Hensen's node and, therefore, acts like a Nieuwkoop Center. These findings increase our understanding of the mechanism of notochord reconstitution, provide new information and a novel model system for studying the induction of the organizer and reveal the potential of the epiblast to regulate its cell fate and patterns of gene expression during late gastrula/early neurula stage in higher vertebrates.

Methylation and expression of the Myo D1 determination gene

1990 ◽  
Vol 326 (1235) ◽  
pp. 277-284 ◽  
Keyword(s):  
De Novo ◽  
Cell Types ◽  
Model System ◽  
Parental Line ◽  
Molecular Control ◽  
Embryo Cells ◽  
End Stage ◽  
Derivatives Of

Mouse embryo cells induced to differentiate with the demethylating agent 5- azacytidine represent an excellent model system to investigate the molecular control of development. Clonal derivatives of 10T1/2 cells that have become determined to the myogenic or adipogenic lineages can be isolated from the multipotential parental line after drug treatment. These determined derivatives can be cultured indefinitely and will differentiate into end-stage phenotypes on appropriate stimulation. A gene called Myo D1, recently isolated from such a myoblast line, will confer myogenesis when expressed in 10T1/2 or other cell types (Davis et al. 1987). The cDNA for Myo D1 contains a large number of CpG sequences and the gene is relatively methylated in 10T1/2 cells and an adipocyte derivative, but is demethylated in myogenic derivatives. Myo D1 may therefore be subject to methylation control in vitro . On the other hand, preliminary observations suggest that Myo D1 is not methylated at CCGG sites in vivo so that a de novo methylation event may have occurred in vitro . These observations may have significance in the establishment of immortal cell lines and tumours.

Reconstitution of the organizer is both sufficient and required to re-establish a fully patterned body plan in avian embryos

Development ◽  
1999 ◽  
Vol 126 (11) ◽  
pp. 2461-2473 ◽  
Author(s):  
S. Yuan ◽  
G.C. Schoenwolf
Keyword(s):  
Primitive Streak ◽  
Body Plan ◽  
The Body ◽  
Tissue Type ◽  
Avian Embryos ◽  
Specific Differentiation ◽  
Neurula Stage

Lateral blastoderm isolates (LBIs) at the late gastrula/early neurula stage (i.e., stage 3d/4) that lack Hensen's node (organizer) and primitive streak can reconstitute a functional organizer and primitive streak within 10–12 hours in culture. We used LBIs to study the initiation and regionalization of the body plan. A complete body plan forms in each LBI by 36 hours in culture, and normal craniocaudal, dorsoventral, and mediolateral axes are re-established. Thus, reconstitution of the organizer is sufficient to re-establish a fully patterned body plan. LBIs can be modified so that reconstitution of the organizer does not occur. In such modified LBIs, tissue-type specific differentiation (with the exception of heart differentiation) and reconstitution of the body plan fail to occur. Thus, the reconstitution of the organizer is not only sufficient to re-establish a fully patterned body plan, it is also required. Finally, our results show that formation and patterning of the heart is under the control of the organizer, and that such control is exerted during the early to mid-gastrula stages (i.e., stages 2–3a), prior to formation of the fully elongated primitive streak.

630: A Novel Model System for the Treatment of Renal Cancer by Nonmyeloablative Allogeneic Hemopoietic Cell Transplantation Using Cyclophosphamide in Mice

2005 ◽  
Vol 173 (4S) ◽  
pp. 172-172
Author(s):  
Masatoshi Eto ◽  
Masahiko Harano ◽  
Katsunori Tatsugami ◽  
Hirofumi Koga ◽  
Seiji Naito
Keyword(s):  
Cell Transplantation ◽  
Renal Cancer ◽  
Model System ◽  
Hemopoietic Cell ◽  
Novel Model

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.

Investigation on the origin of the definitive endoderm in the rat embryo

Development ◽  
1974 ◽  
Vol 32 (2) ◽  
pp. 445-459
Author(s):  
B. Levak-Švajger ◽  
A. Švajger
Keyword(s):  
Primitive Streak ◽  
Definitive Endoderm ◽  
Rat Embryo ◽  
Chick Blastoderm ◽  
Germ Layers ◽  
Kidney Capsule ◽  
Rat Embryos ◽  
Endodermal Cells ◽  
Derivatives Of

Single germ layers (or combinations of two of them) were isolated from the primitive streak and the head-fold stage rat embryos and grown for 15 days under the kidney capsule of syngeneic adult animals. The resulting teratomas were examined histologically for the presence of mature tissues, with special emphasis on derivatives of the primitive gut. Ectoderm isolated together with the initial mesodermal wings at the primitive streak stage gave rise to tissue derivatives of all three definitive germ layers. Derivatives of the primitive gut were regularly present in these grafts. At the head-fold stage, isolated ectoderm (including the region of the primitive streak) differentiated into ectodermal and mesodermal derivatives only. Endoderm isolated at the primitive streak stage did not develop when grafted and was always completely resorbed. At the head-fold stage, however, definitive endoderm differentiated into derivatives of the primitive gut if grafted together with adjacent mesoderm. These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm.

A regulatory network of microRNAs confers lineage commitment during early developmental trajectories of B and T lymphocytes

2021 ◽  
Vol 118 (46) ◽  
pp. e2104297118
Author(s):  
Sameena Nikhat ◽  
Anurupa D. Yadavalli ◽  
Arpita Prusty ◽  
Priyanka K. Narayan ◽  
Dasaradhi Palakodeti ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Lymphocytes ◽  
Cell Fate ◽  
T Lymphocyte ◽  
De Novo ◽  
Gene Expression Pattern ◽  
Lymphocyte Development ◽  
Motif Analysis ◽  
Differentiation Potential ◽  
B And T Lymphocytes

The commitment of hematopoietic multipotent progenitors (MPPs) toward a particular lineage involves activation of cell type–specific genes and silencing of genes that promote alternate cell fates. Although the gene expression programs of early–B and early–T lymphocyte development are mutually exclusive, we show that these cell types exhibit significantly correlated microRNA (miRNA) profiles. However, their corresponding miRNA targetomes are distinct and predominated by transcripts associated with natural killer, dendritic cell, and myeloid lineages, suggesting that miRNAs function in a cell-autonomous manner. The combinatorial expression of miRNAs miR-186-5p, miR-128-3p, and miR-330-5p in MPPs significantly attenuates their myeloid differentiation potential due to repression of myeloid-associated transcripts. Depletion of these miRNAs caused a pronounced de-repression of myeloid lineage targets in differentiating early–B and early–T cells, resulting in a mixed-lineage gene expression pattern. De novo motif analysis combined with an assay of promoter activities indicates that B as well as T lineage determinants drive the expression of these miRNAs in lymphoid lineages. Collectively, we present a paradigm that miRNAs are conserved between developing B and T lymphocytes, yet they target distinct sets of promiscuously expressed lineage-inappropriate genes to suppress the alternate cell-fate options. Thus, our studies provide a comprehensive compendium of miRNAs with functional implications for B and T lymphocyte development.

scholarly journals A novel model system for studying the double-edged roles of nitric oxide production in pancreatic cancer growth and metastasis

Oncogene ◽  
2003 ◽  
Vol 22 (12) ◽  
pp. 1771-1782 ◽  
Author(s):  
Bailiang Wang ◽  
Daoyan Wei ◽  
Vanessa E Crum ◽  
Erica L Richardson ◽  
Henry H Xiong ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Pancreatic Cancer ◽  
Model System ◽  
Cancer Growth ◽  
Nitric Oxide Production ◽  
Oxide Production ◽  
Novel Model

scholarly journals Molecularly Engineered PEG Hydrogels: A Novel Model System for Proteolytically Mediated Cell Migration

2005 ◽  
Vol 89 (2) ◽  
pp. 1374-1388 ◽  
Author(s):  
G.P. Raeber ◽  
M.P. Lutolf ◽  
J.A. Hubbell
Keyword(s):  
Cell Migration ◽  
Model System ◽  
Peg Hydrogels ◽  
Novel Model

scholarly journals Prediction and control of symmetry breaking in embryoid bodies by environment and signal integration

2018 ◽  
Author(s):  
Naor Sagy ◽  
Shaked Slovin ◽  
Maya Allalouf ◽  
Maayan Pour ◽  
Gaya Savyon ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Developmental Process ◽  
Primitive Streak ◽  
Early Embryo ◽  
Embryoid Bodies ◽  
Neighboring Cell ◽  
Contact Points

AbstractDuring early embryogenesis, mechanical signals, localized biochemical signals and neighboring cell layers interaction coordinate around anteroposterior axis determination and symmetry breaking. Deciphering their relative roles, which are hard to tease apart in vivo, will enhance our understanding of how these processes are driven. In recent years, in vitro 3D models of early mammalian development, such as embryoid bodies (EBs) and gastruloids, were successful in mimicking various aspects of the early embryo, providing high throughput accessible systems for studying the basic rules shaping cell fate and morphology during embryogenesis. Using Brachyury (Bry), a primitive streak and mesendoderm marker in EBs, we study how contact, biochemical and neighboring cell cues affect the positioning of a primitive streak-like locus, determining the AP axis. We show that a Bry-competent layer must be formed in the EB before Bry expression initiates, and that Bry onset locus selection depends on contact points of the EB with its surrounding. We can maneuver Bry onset to occur at a specific locus, a few loci, or in an isotropic peripheral pattern. By spatially separating contact and biochemical signal sources, we show these two modalities can be integrated by the EB to generate a single Bry locus. Finally, we show Foxa2+ cells are predictive of the future location of Bry onset, demonstrating an earlier symmetry-breaking event. By delineating the temporal signaling pathway dependencies of Bry and Foxa2, we were able to selectively abolish either, or spatially decouple the two cell types during EB differentiation. These findings demonstrate multiple inputs integration during an early developmental process, and may prove valuable in directing in vitro differentiation.

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