Body axis determination during early development in amphibians

1992 ◽  
Vol 70 (10-11) ◽  
pp. 875-891 ◽  
Author(s):  
Pierre Savard
Keyword(s):  
Retinoic Acid ◽  
Cell Communication ◽  
The Body ◽  
Specific Gene ◽  
Cellular Interactions ◽  
Cell Stage ◽  
Heterogeneous Distribution ◽  
Spemann's Organizer ◽  
Cytoplasmic Content ◽  
Set Up

The specification of the main axes of the body is a phenomenon based on cell communication and is among the early crucial events of embryonic development. Upon fertilization, the amphibian egg reorganizes its cytoplasmic content, leading to the establishment of the future dorsal–ventral axis of the body. Heterogeneous distribution of maternal components confers cellular regionalization after only a few mitoses. Development up to the 4000-cell stage proceeds almost entirely on maternal materials, and during this period there is remodeling of the chromatin to set up specific gene expression in various regions of the embryo. The zygote at this stage has already undertaken cellular interactions leading to mesoderm formation and regionalization. Dorsal mesodermal components then induce the formation of the Spemann's organizer, a structure directly involved in the specification of the anterior–posterior axis of the embryo (head to tail). Molecular analysis of these phenomena has allowed the identification of growth-factor-like and transcription-factor-like proteins that have characteristics typical of specification factors. We will review the recent advances on these molecules and will also discuss the putative role of retinoic acid as a posteriorizing agent.Key words: chromatin remodeling, cellular regionalization, homeobox, inducing factor, retinoic acid.

scholarly journals Pannexin 1 influences lineage specification of human iPSCs

2021 ◽  
Author(s):  
Rebecca J. Noort ◽  
Grace A. Christopher ◽  
Jessica L. Esseltine
Keyword(s):  
Cell Fate ◽  
Cell Communication ◽  
Cell Lineage ◽  
The Body ◽  
Human Embryos ◽  
Lineage Specification ◽  
Cell Stage ◽  
Cell Fate Decisions ◽  
Pannexin 1 ◽  
Human Ipscs

AbstractEvery single cell in the body communicates with nearby cells to locally organize activities with their neighbors and dysfunctional cell-cell communication can be detrimental during cell lineage commitment, tissue patterning and organ development. Pannexin channels (PANX1, PANX2, PANX3) facilitate purinergic paracrine signaling through the passage of messenger molecules out of cells. PANX1 is widely expressed throughout the body and has recently been identified in human oocytes as well as 2 and 4-cell stage human embryos. Given its abundance across multiple adult tissues and its expression at the earliest stages of human development, we sought to understand whether PANX1 impacts human induced pluripotent stem cells (iPSCs) or plays a role in cell fate decisions. Western blot, immunofluorescence and flow cytometry reveal that PANX1 is expressed in iPSCs as well as all three germ lineages derived from these cells: ectoderm, endoderm, and mesoderm. PANX1 demonstrates differential glycosylation patterns and subcellular localization across the germ lineages. Using CRISPR-Cas9 gene ablation, we find that loss of PANX1 has no obvious impact on iPSC morphology, survival, or pluripotency gene expression. However, PANX1 knockout iPSCs exhibit apparent lineage specification bias during 2-dimensional and 3-dimensional spontaneous differentiation into the three germ lineages. Indeed, loss of PANX1 significantly decreases the proportion of ectodermal cells within spontaneously differentiated cultures, while endodermal and mesodermal representation is increased in PANX1 knockout cells. Importantly, PANX1 knockout iPSCs are fully capable of differentiating toward each specific lineage when exposed to the appropriate external signaling pressures, suggesting that although PANX1 influences germ lineage specification, it is not essential to this process.Graphical abstract

The system specifying body position in the early development of Xenopus, and its response to early perturbations.

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 69-87
Author(s):  
Jonathan Cooke
Keyword(s):  
Early Development ◽  
Body Position ◽  
Bilateral Symmetry ◽  
The Body ◽  
Spatial Profile ◽  
Cell Stage ◽  
Larval Stages ◽  
Positional System ◽  
Set Up ◽  
Pattern Specification

Evidence is presented that the system setting up preliminary specifications for contributions to the axial body plan, across vegetal regions of the Xenopus embryo, acts in a widespread way at early stages. Mechanisms that regulate the spatial profile of this primary positional variable, and thus ensure the constancy and harmony of the body plans normally achieved, have lost this integrative ability by the 4-cell stage one hour after the plasm shifts that precede first cleavage and symmetrize the egg. Abnormal, partial or distorted profiles of the positional system across whole eggs or isolates, recorded by these times, are retained to give correspondingly partial or imbalanced mes/endodermal pattern at tailbud larval stages. There is evidence that subsequent ‘back-up’ positional interactions, which can heal gross positional discontinuities in isolated presumptive lateral half-eggs and so restore bilateral symmetry, also do this at the price of loss of complete pattern specification. This is probably because of an asymmetrical principle whereby relatively activated (dorsoanterior specified) material can raise the level of originally posterior material on contact, whereas the reverse interaction cannot occur. The observations are discussed in relation to apparently different behaviour in certain other amphibian embryos, and to our knowledge of other positional interactions, normal and also experimentally provoked, such as those that set up the germ layers.

scholarly journals Pannexin 1 Influences Lineage Specification of Human iPSCs

2021 ◽  
Vol 9 ◽  
Author(s):  
Rebecca J. Noort ◽  
Grace A. Christopher ◽  
Jessica L. Esseltine
Keyword(s):  
Cell Fate ◽  
Gene Knockout ◽  
Cell Communication ◽  
Cell Lineage ◽  
The Body ◽  
Human Embryos ◽  
Lineage Specification ◽  
Cell Stage ◽  
Cell Fate Decisions ◽  
Human Ipscs

Every single cell in the body communicates with nearby cells to locally organize activities with their neighbors and dysfunctional cell-cell communication can be detrimental during cell lineage commitment, tissue patterning and organ development. Pannexin channels (PANX1, PANX2, and PANX3) facilitate purinergic paracrine signaling through the passage of messenger molecules out of cells. PANX1 is widely expressed throughout the body and has recently been identified in human oocytes as well as 2 and 4-cell stage human embryos. Given its abundance across multiple adult tissues and its expression at the earliest stages of human development, we sought to understand whether PANX1 impacts human induced pluripotent stem cells (iPSCs) or plays a role in cell fate decisions. Western blot, immunofluorescence and flow cytometry reveal that PANX1 is expressed in iPSCs as well as all three germ lineages derived from these cells: ectoderm, endoderm, and mesoderm. PANX1 demonstrates differential glycosylation patterns and subcellular localization across the germ lineages. Using CRISPR-Cas9 gene ablation, we find that loss of PANX1 has no obvious impact on iPSC morphology, survival, or pluripotency gene expression. However, PANX1 gene knockout iPSCs exhibit apparent lineage specification bias under 3-dimensional spontaneous differentiation into the three germ lineages. Indeed, loss of PANX1 increases representation of endodermal and mesodermal populations in PANX1 knockout cells. Importantly, PANX1 knockout iPSCs are fully capable of differentiating toward each specific lineage when exposed to the appropriate external signaling pressures, suggesting that although PANX1 influences germ lineage specification, it is not essential to this process.

Teratogene und metamorphosehemmende Wirkung von Retinsäure in Ciona intestinalis / Teratogenic and Metamorphosis-Inhibiting Activity of Retinoic Acid in Ciona intestinalis

1991 ◽  
Vol 46 (11-12) ◽  
pp. 1094-1100 ◽  
Author(s):  
J. Manuel Denucé
Keyword(s):  
Retinoic Acid ◽  
Ciona Intestinalis ◽  
The Body ◽  
Cell Stage ◽  
Sea Squirt ◽  
All Trans Retinoic Acid ◽  
Settlement And Metamorphosis ◽  
Vitamin A Derivative ◽  
Early Gastrula

Exposure of embryos of the sea squirt, Ciona intestinalis, to all-trans-retinoic acid (between 10-5 and 10-7 m) causes specific malformations of the larvae and suppression of settlement and metamorphosis. Whether the vitamin A derivative was administered at the 2-cell stage, or at the early gastrula stage did not affect the nature or the extent of the ensuing anomalies. Malformations include a dorsal bulge of the body, an irregular disposition of ocellar pigment, and a twisted tail. Treated larvae have no statocyst pigment. There is also a reduction in size of the body, compared to control larvae. Retinoic acid retarded hatching, or even blocked it (at 10-5m). Obviously retinoic acid interferes with the induction of metamorphosis, possibly through neutralizing one or more factor|s responsible for settlement and metamorphosis. The possible role of thyroxin in these processes is being critically evaluated.

scholarly journals Glucocorticoid Receptor β (GRβ): Beyond Its Dominant-Negative Function

2021 ◽  
Vol 22 (7) ◽  
pp. 3649
Author(s):  
Patricia Ramos-Ramírez ◽  
Omar Tliba
Keyword(s):  
Current Knowledge ◽  
Inflammatory Diseases ◽  
Cell Communication ◽  
Cell Types ◽  
The Body ◽  
Dominant Negative ◽  
Negative Effects ◽  
Independent Manner ◽  
Distinct Cell ◽  
Induced Apoptosis

Glucocorticoids (GCs) act via the GC receptor (GR), a receptor ubiquitously expressed in the body where it drives a broad spectrum of responses within distinct cell types and tissues, which vary in strength and specificity. The variability of GR-mediated cell responses is further extended by the existence of GR isoforms, such as GRα and GRβ, generated through alternative splicing mechanisms. While GRα is the classic receptor responsible for GC actions, GRβ has been implicated in the impairment of GRα-mediated activities. Interestingly, in contrast to the popular belief that GRβ actions are restricted to its dominant-negative effects on GRα-mediated responses, GRβ has been shown to have intrinsic activities and “directly” regulates a plethora of genes related to inflammatory process, cell communication, migration, and malignancy, each in a GRα-independent manner. Furthermore, GRβ has been associated with increased cell migration, growth, and reduced sensitivity to GC-induced apoptosis. We will summarize the current knowledge of GRβ-mediated responses, with a focus on the GRα-independent/intrinsic effects of GRβ and the associated non-canonical signaling pathways. Where appropriate, potential links to airway inflammatory diseases will be highlighted.

scholarly journals Insights into how environment shapes post-mortem RNA transcription in mouse brain

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Raphael Severino Bonadio ◽  
Larissa Barbosa Nunes ◽  
Patricia Natália S. Moretti ◽  
Juliana Forte Mazzeu ◽  
Stefano Cagnin ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Mouse Brain ◽  
Molecular Mechanisms ◽  
Cell Communication ◽  
Rna Degradation ◽  
The Body ◽  
Biological Processes ◽  
Post Mortem ◽  
Gene Expression Alterations ◽  
Upregulated Genes

AbstractMost biological features that occur on the body after death were already deciphered by traditional medicine. However, the molecular mechanisms triggered in the cellular microenvironment are not fully comprehended yet. Previous studies reported gene expression alterations in the post-mortem condition, but little is known about how the environment could influence RNA degradation and transcriptional regulation. In this work, we analysed the transcriptome of mouse brain after death under three concealment simulations (air exposed, buried, and submerged). Our analyses identified 2,103 genes differentially expressed in all tested groups 48 h after death. Moreover, we identified 111 commonly upregulated and 497 commonly downregulated genes in mice from the concealment simulations. The gene functions shared by the individuals from the tested environments were associated with RNA homeostasis, inflammation, developmental processes, cell communication, cell proliferation, and lipid metabolism. Regarding the altered biological processes, we identified that the macroautophagy process was enriched in the upregulated genes and lipid metabolism was enriched in the downregulated genes. On the other hand, we also described a list of biomarkers associated with the submerged and buried groups, indicating that these environments can influence the post-mortem RNA abundance in its particular way.

scholarly journals Retinoic acid signaling is critical during the totipotency window in early mammalian development

2021 ◽  
Author(s):  
Ane Iturbide ◽  
Mayra L. Ruiz Tejeda Segura ◽  
Camille Noll ◽  
Kenji Schorpp ◽  
Ina Rothenaigner ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Regulatory Networks ◽  
Es Cells ◽  
Embryonic Stem ◽  
Mammalian Development ◽  
Cell Stage ◽  
Cell Potential ◽  
Cellular Models ◽  
Early Embryos ◽  
Genome Activation

AbstractTotipotent cells hold enormous potential for regenerative medicine. Thus, the development of cellular models recapitulating totipotent-like features is of paramount importance. Cells resembling the totipotent cells of early embryos arise spontaneously in mouse embryonic stem (ES) cell cultures. Such ‘2-cell-like-cells’ (2CLCs) recapitulate 2-cell-stage features and display expanded cell potential. Here, we used 2CLCs to perform a small-molecule screen to identify new pathways regulating the 2-cell-stage program. We identified retinoids as robust inducers of 2CLCs and the retinoic acid (RA)-signaling pathway as a key component of the regulatory circuitry of totipotent cells in embryos. Using single-cell RNA-seq, we reveal the transcriptional dynamics of 2CLC reprogramming and show that ES cells undergo distinct cellular trajectories in response to RA. Importantly, endogenous RA activity in early embryos is essential for zygotic genome activation and developmental progression. Overall, our data shed light on the gene regulatory networks controlling cellular plasticity and the totipotency program.

scholarly journals Targeted disruption of retinoic acid receptor alpha (RAR alpha) and RAR gamma results in receptor-specific alterations in retinoic acid-mediated differentiation and retinoic acid metabolism.

1995 ◽  
Vol 15 (2) ◽  
pp. 843-851 ◽  
Author(s):  
J F Boylan ◽  
T Lufkin ◽  
C C Achkar ◽  
R Taneja ◽  
P Chambon ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Retinoic Acid Receptor ◽  
Specific Gene ◽  
Cell Type ◽  
Targeted Disruption ◽  
F9 Cells ◽  
Retinoid Receptors ◽  
Alpha Gene ◽  
Polar Derivatives ◽  
Crabp Ii

F9 embryonic teratocarcinoma stem cells differentiate into an epithelial cell type called extraembryonic endoderm when treated with retinoic acid (RA), a derivative of retinol (vitamin A). This differentiation is presumably mediated through the actions of retinoid receptors, the RARs and RXRs. To delineate the functions of each of the different retinoid receptors in this model system, we have generated F9 cell lines in which both copies of either the RAR alpha gene or the RAR gamma gene are disrupted by homologous recombination. The absence of RAR alpha is associated with a reduction in the RA-induced expression of both the CRABP-II and Hoxb-1 (formerly 2.9) genes. The absence of RAR gamma is associated with a loss of the RA-inducible expression of the Hoxa-1 (formerly Hox-1.6), Hoxa-3 (formerly Hox-1.5), laminin B1, collagen IV (alpha 1), GATA-4, and BMP-2 genes. Furthermore, the loss of RAR gamma is associated with a reduction in the metabolism of all-trans-RA to more polar derivatives, while the loss of RAR alpha is associated with an increase in metabolism of RA relative to wild-type F9 cells. Thus, each of these RARs exhibits some specificity with respect to the regulation of differentiation-specific gene expression. These results provide an explanation for the expression of multiple RAR types within one cell type and suggest that each RAR has specific functions.

The origins of primitive blood in Xenopus: implications for axial patterning

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 423-434 ◽  
Author(s):  
M.C. Lane ◽  
W.C. Smith
Keyword(s):  
Xenopus Laevis ◽  
Marginal Zone ◽  
Cell Stage ◽  
Axial Patterning ◽  
Xenopus Embryos ◽  
Spemann's Organizer ◽  
Dorsal Mesoderm

The marginal zone in Xenopus laevis is proposed to be patterned with dorsal mesoderm situated near the upper blastoporal lip and ventral mesoderm near the lower blastoporal lip. We determined the origins of the ventralmost mesoderm, primitive blood, and show it arises from all vegetal blastomeres at the 32-cell stage, including blastomere C1, a progenitor of Spemann's organizer. This demonstrates that cells located at the upper blastoporal lip become ventral mesoderm, not solely dorsal mesoderm as previously believed. Reassessment of extant fate maps shows dorsal mesoderm and dorsal endoderm descend from the animal region of the marginal zone, whereas ventral mesoderm descends from the vegetal region of the marginal zone, and ventral endoderm descends from cells located vegetal of the bottle cells. Thus, the orientation of the dorsal-ventral axis of the mesoderm and endoderm is rotated 90(degrees) from its current portrayal in fate maps. This reassessment leads us to propose revisions in the nomenclature of the marginal zone and the orientation of the axes in pre-gastrula Xenopus embryos.

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

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