scholarly journals The Xenopus MyoD gene: an unlocalised maternal mRNA predates lineage-restricted expression in the early embryo

Development ◽  
1990 ◽  
Vol 108 (4) ◽  
pp. 669-680 ◽  
Author(s):  
R.P. Harvey
Keyword(s):  
Gene Expression ◽  
Cultured Cells ◽  
Early Response ◽  
Early Embryo ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Early Expression ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors ◽  
Myod Gene

Expression of the mouse MyoD gene appears to represent a critical point in the commitment of cultured cells to muscle. In Xenopus, myogenic commitment begins during mesoderm induction which is initiated early in development by endogenous growth factors. To study MyoD gene expression during induction, a Xenopus MyoD gene and homologous cDNAs were selected from Xenopus libraries and analysed. Two different cDNAs have been sequenced. They code for proteins closely related to each other and to mouse MyoD and are likely to be expressed from duplicated Xenopus MyoD genes. Surprisingly, MyoD mRNA is first detected during oogenesis and the maternal species is not localized exclusively to the region of the blastula fated to muscle. Zygotic MyoD mRNA accumulates slowly above maternal levels beginning at the MBT and new transcripts are localized to the somitic mesoderm. Expression outside of somites has been detected in developing heads of tailbud embryos and can be induced in blastula animal pole explants treated with mesoderm-inducing factors. The early expression of MyoD in Xenopus development suggests that it may play a part in the induction of muscle mesoderm and generally strengthens the evidence that MyoD is determinative in muscle commitment. In addition, the initiation of MyoD transcription at the MBT and its stimulation by mesoderm-inducing factors implies that MyoD gene expression is an immediate early response to mesoderm induction.

Analysis of competence and of Brachyury autoinduction by use of hormone-inducible Xbra

Development ◽  
1997 ◽  
Vol 124 (11) ◽  
pp. 2225-2234 ◽  
Author(s):  
M. Tada ◽  
M.A. O'Reilly ◽  
J.C. Smith
Keyword(s):  
Glucocorticoid Receptor ◽  
Target Genes ◽  
Early Embryo ◽  
Fate Map ◽  
Animal Pole ◽  
Reading Frame ◽  
Xenopus Development ◽  
Series Of Experiments ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

Analysis of gene function in Xenopus development frequently involves over-expression experiments, in which RNA encoding the protein of interest is microinjected into the early embryo. By taking advantage of the fate map of Xenopus, it is possible to direct expression of the protein to particular regions of the embryo, but it has not been possible to exert control over the timing of expression; the protein is translated immediately after injection. To overcome this problem in our analysis of the role of Brachyury in Xenopus development, we have, like Kolm and Sive (1995; Dev. Biol. 171, 267–272), explored the use of hormone-inducible constructs. Animal pole regions derived from embryos expressing a fusion protein (Xbra-GR) in which the Xbra open reading frame is fused to the ligand-binding domain of the human glucocorticoid receptor develop as atypical epidermis, presumably because Xbra is sequestered by the heat-shock apparatus of the cell. Addition of dexamethasone, which binds to the glucocorticoid receptor and releases Xbra, causes formation of mesoderm. We have used this approach to investigate the competence of animal pole explants to respond to Xbra-GR, and have found that competence persists until late gastrula stages, even though by this time animal caps have lost the ability to respond to mesoderm-inducing factors such as activin and FGF. In a second series of experiments, we demonstrate that Xbra is capable of inducing its own expression, but that this auto-induction requires intercellular signals and FGF signalling. Finally, we suggest that the use of inducible constructs may assist in the search for target genes of Brachyury.

scholarly journals Gastrulation movements provide an early marker of mesoderm induction in Xenopus laevis

Development ◽  
1987 ◽  
Vol 101 (2) ◽  
pp. 339-349 ◽  
Author(s):  
K. Symes ◽  
J.C. Smith
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Early Response ◽  
Model System ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Inductive Interaction ◽  
Vegetal Pole ◽  
Pole Cells ◽  
General Appearance

The first inductive interaction in amphibian development is mesoderm induction, in which an equatorial mesodermal rudiment is induced from the animal hemisphere under the influence of a signal from vegetal pole blastomeres. We have recently discovered that the Xenopus XTC cell line secretes a factor which has the properties we would expect of a mesoderm-inducing factor. In this paper, we show that an early response to this factor by isolated Xenopus animal pole regions is a change in shape, involving elongation and constriction. We show by several criteria, including general appearance, timing, rate of elongation and the nonrequirement for cell division that these movements resemble the events of gastrulation. We also demonstrate that the movements provide an early, simple and reliable indicator of mesoderm induction and are of use in providing a ‘model system’ for the study of mesoderm induction and gastrulation. For example, we show that the timing of gastrulation movements does not depend upon the time of receipt of a mesoderm-induction signal, but on an intrinsic gastrulation ‘clock’ which is present even in those animal pole cells that would not nomally require it.

Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderm-inducing growth factors, may play a role in ventral mesodermal patterning during embryogenesis

Development ◽  
1991 ◽  
Vol 111 (4) ◽  
pp. 1045-1055 ◽  
Author(s):  
J.L. Christian ◽  
J.A. McMahon ◽  
A.P. McMahon ◽  
R.T. Moon
Keyword(s):  
Growth Factors ◽  
Cell Fate ◽  
Ectopic Expression ◽  
Mesoderm Induction ◽  
Related Gene ◽  
Mesodermal Cell ◽  
Peptide Growth Factors ◽  
Basic Body ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors

In amphibian embryos, formation of the basic body plan depends on positional differences in the mesoderm. Although peptide growth factors involved in mesoderm induction have tentatively been identified, additional signals are required to generate pattern in this tissue. We have isolated a Xenopus cDNA for a Wnt-1 related gene, designated Xwnt-8, which is activated in response to mesoderm-inducing growth factors. Xwnt-8 transcripts are transiently expressed, being most abundant during gastrulation at which time expression is confined primarily to ventral mesodermal cells. Embryos dorsoanteriorized by exposure to lithium exhibit greatly reduced levels of Xwnt-8 mRNA, supporting a correlation between Xwnt-8 expression and a ventral mesodermal cell fate. Surprisingly, ectopic expression of Xwnt-8 in embryos causes a dorsoanterior-enhanced phenotype. These findings suggest that Xwnt-8 may be a secondary signalling agent which is produced in response to mesoderm-inducing factors and is involved in the early steps of mesodermal patterning.

FGF is a prospective competence factor for early activin-type signals in Xenopus mesoderm induction

Development ◽  
1995 ◽  
Vol 121 (8) ◽  
pp. 2429-2437 ◽  
Author(s):  
R.A. Cornell ◽  
T.J. Musci ◽  
D. Kimelman
Keyword(s):  
Ectopic Expression ◽  
Equatorial Region ◽  
Mesoderm Induction ◽  
Normal Pattern ◽  
Fgf Receptor ◽  
Competence Factor ◽  
Low Levels ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors ◽  
Cellular Competence

Normal pattern formation during embryonic development requires the regulation of cellular competence to respond to inductive signals. In the Xenopus blastula, vegetal cells release mesoderm-inducing factors but themselves become endoderm, suggesting that vegetal cells may be prevented from expressing mesodermal genes in response to the signals that they secrete. We show here that addition of low levels of basic fibroblast growth factor (bFGF) induces the ectopic expression of the mesodermal markers Xbra, MyoD and muscle actin in vegetal explants, even though vegetal cells express low levels of the FGF receptor. Activin, a potent mesoderm-inducing agent in explanted ectoderm (animal explants), does not induce ectopic expression of these markers in vegetal explants. However, activin-type signaling is present in vegetal cells, since the vegetal expression of Mix.1 and goosecoid is inhibited by the truncated activin receptor. These results, together with the observation that FGF is required for mesoderm induction by activin, support our proposal that a maternal FGF acts at the equator as a competence factor, permitting equatorial cells to express mesoderm in response to an activin-type signal. The overlap of FGF and activin-type signaling is proposed to restrict mesoderm to the equatorial region.

scholarly journals CRISPR-on for activation of endogenous SMARCA4 and TFAP2C expression in bovine embryos

Reproduction ◽  
2020 ◽  
Vol 159 (6) ◽  
pp. 767-778
Author(s):  
Virginia Savy ◽  
Virgilia Alberio ◽  
Natalia G Canel ◽  
Laura D Ratner ◽  
Maria I Gismondi ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Fate ◽  
Embryo Development ◽  
Transcriptional Activation ◽  
Cultured Cells ◽  
Early Embryo ◽  
Bovine Embryos ◽  
Endogenous Gene ◽  
Cell Fate Decisions ◽  
Mammalian Embryos

CRISPR-mediated transcriptional activation, also known as CRISPR-on, has proven efficient for activation of individual or multiple endogenous gene expression in cultured cells from several species. However, the potential of CRISPR-on technology in preimplantation mammalian embryos remains to be explored. Here, we report for the first time the successful modulation of endogenous gene expression in bovine embryos by using the CRISPR-on system. As a proof of principle, we targeted the promoter region of either SMARCA4 or TFAP2C genes, transcription factors implicated in trophoblast lineage commitment during embryo development. We demonstrate that CRISPR-on provides temporal control of endogenous gene expression in bovine embryos, by simple cytoplasmic injection of CRISPR RNA components into one cell embryos. dCas9VP160 activator was efficiently delivered and accurately translated into protein, being detected in the nucleus of all microinjected blastomeres. Our approach resulted in the activation of SMARCA expression shortly after microinjection, with a consequent effect on downstream differentiation promoting factors, such as TFAP2C and CDX2. Although targeting of TFAP2C gene did not result in a significant increase in TFAP2C expression, there was a profound induction in CDX2 expression on day 2 of development. Finally, we demonstrate that CRISPR-on system is suitable for gene expression modulation during the preimplantation period, since no detrimental effect was observed on microinjected embryo development. This study constitutes a first step toward the application of the CRISPR-on system for the study of early embryo cell fate decisions in cattle and other mammalian embryos, as well as to design novel strategies that may lead to an improved trophectoderm development.

scholarly journals Quantitative comparison of mesoderm inducing factors in xenopus

1989 ◽  
Vol 27 ◽  
pp. 53
Author(s):  
J.B.A. Green ◽  
G. Howes ◽  
M. Yaqoob ◽  
J. Cooke ◽  
J.C. Smith
Keyword(s):  
Quantitative Comparison ◽  
Inducing Factors ◽  
Mesoderm Inducing Factors
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