scholarly journals Ras-Mediated FGF Signaling Is Required for the Formation of Posterior but Not Anterior Neural Tissue in Xenopus laevis

2000 ◽  
Vol 227 (1) ◽  
pp. 183-196 ◽  
Author(s):  
Stephen Ribisi ◽  
Francesca V. Mariani ◽  
Emil Aamar ◽  
Teresa M. Lamb ◽  
Dale Frank ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Neural Tissue ◽  
Fgf Signaling

scholarly journals Xbra3 Induces Mesoderm and Neural Tissue in Xenopus laevis

2000 ◽  
Vol 222 (2) ◽  
pp. 405-419 ◽  
Author(s):  
C.F. Strong ◽  
M.W. Barnett ◽  
D. Hartman ◽  
E.A. Jones ◽  
D. Stott
Keyword(s):  
Xenopus Laevis ◽  
Neural Tissue

scholarly journals Differential perturbations in the morphogenesis of anterior structures induced by overexpression of truncated XB- and N-cadherins in Xenopus embryos.

1994 ◽  
Vol 127 (2) ◽  
pp. 521-535 ◽  
Author(s):  
S Dufour ◽  
J P Saint-Jeannet ◽  
F Broders ◽  
D Wedlich ◽  
J P Thiery
Keyword(s):  
Xenopus Laevis ◽  
Neural Development ◽  
Neural Tissue ◽  
Cell Stage ◽  
Crucial Step ◽  
Tissue Integrity ◽  
Xenopus Embryos ◽  
Additive Perturbation ◽  
Early Neurogenesis ◽  
Anchor Structure

Cadherins, a family of Ca-dependent adhesion molecules, have been proposed to act as regulators of morphogenetic processes and to be major effectors in the maintenance of tissue integrity. In this study, we have compared the effects of the expression of two truncated cadherins during early neurogenesis in Xenopus laevis. mRNA encoding deleted forms of XB- and N-cadherin lacking most of the extracellular domain were injected into the four animal dorsal blastomeres of 32-cell stage Xenopus embryos. These truncated cadherins altered the cohesion of cells derived from the injected blastomeres and induced morphogenetic defects in the anterior neural tissue to which they chiefly contributed. Truncated XB-cadherin was more efficient than N-cadherin in inducing these perturbations. Moreover, the coexpression of both truncated cadherins had additive perturbation effects on neural development. The two truncated cadherins can interact with the three known catenins, but with distinct affinities. These results suggest that the adhesive signal mediated by cadherins can be perturbed by overexpressing their cytoplasmic domains by competing with different affinity with catenins and/or a common anchor structure. Therefore, the correct regulation of cadherin function through the cytoplasmic domain appears to be a crucial step in the formation of the neural tissue.

scholarly journals Identification of a novel xPAK1 partner important for proper FGF signaling in Xenopus laevis

2006 ◽  
Vol 295 (1) ◽  
pp. 435
Author(s):  
Steve Jean ◽  
Michel Tremblay ◽  
Tom Moss
Keyword(s):  
Xenopus Laevis ◽  
Fgf Signaling

Overlapping Expression of Xwnt-3A and Xwnt-1 in Neural Tissue of Xenopus laevis Embryos

1993 ◽  
Vol 155 (1) ◽  
pp. 46-57 ◽  
Author(s):  
S.L. Wolda ◽  
C.J. Moody ◽  
R.T. Moon
Keyword(s):  
Xenopus Laevis ◽  
Neural Tissue ◽  
Xenopus Laevis Embryos

scholarly journals FGF Signaling Is Required for Lens Regeneration in Xenopus laevis

2011 ◽  
Vol 221 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Lisa Fukui ◽  
Jonathan J. Henry
Keyword(s):  
Xenopus Laevis ◽  
Fgf Signaling ◽  
Lens Regeneration

scholarly journals Initiating Hox gene expression: in the early chick neural tube differential sensitivity to FGF and RA signaling subdivides the HoxBgenes in two distinct groups

Development ◽  
2002 ◽  
Vol 129 (22) ◽  
pp. 5103-5115 ◽  
Author(s):  
Sophie Bel-Vialar ◽  
Nobue Itasaki ◽  
Robb Krumlauf
Keyword(s):  
Signaling Pathways ◽  
Neural Tube ◽  
Hox Genes ◽  
Ectopic Expression ◽  
Neural Tissue ◽  
Dominant Negative ◽  
Differential Sensitivity ◽  
Otic Vesicle ◽  
Fgf Signaling ◽  
Retinoid Receptor

Initiation of Hox genes requires interactions between numerous factors and signaling pathways in order to establish their precise domain boundaries in the developing nervous system. There are distinct differences in the expression and regulation of members of Hox genes within a complex suggesting that multiple competing mechanisms are used to initiate their expression domains in early embryogenesis. In this study, by analyzing the response ofHoxB genes to both RA and FGF signaling in neural tissue during early chick embryogenesis (HH stages 7-15), we have defined two distinct groups of Hox genes based on their reciprocal sensitivity to RA or FGF during this developmental period. We found that the expression domain of 5′ members from the HoxB complex (Hoxb6-Hoxb9) can be expanded anteriorly in the chick neural tube up to the level of the otic vesicle following FGF treatment and that these same genes are refractory to RA treatment at these stages. Furthermore, we showed that the chickcaudal-related genes, cdxA and cdxB, are also responsive to FGF signaling in neural tissue and that their anterior expansion is also limited to the level of the otic vesicle. Using a dominant negative form of a Xenopus Cdx gene (XcadEnR) we found that the effect of FGF treatment on 5′ HoxB genes is mediated in part through the activation and function of CDX activity. Conversely, the 3′HoxB genes (Hoxb1 and Hoxb3-Hoxb5) are sensitive to RA but not FGF treatments at these stages. We demonstrated by in ovo electroporation of a dominant negative retinoid receptor construct(dnRAR) that retinoid signaling is required to initiate expression. Elevating CDX activity by ectopic expression of an activated form of aXenopus Cdx gene (XcadVP16) in the hindbrain ectopically activates and anteriorly expands Hoxb4 expression. In a similar manner, when ectopic expression of XcadVP16 is combined with FGF treatment, we found that Hoxb9 expression expands anteriorly into the hindbrain region. Our findings suggest a model whereby, over the window of early development we examined, all HoxB genes are actually competent to interpret an FGF signal via a CDX-dependent pathway. However, mechanisms that axially restrict the Cdx domains of expression, serve to prevent 3′ genes from responding to FGF signaling in the hindbrain. FGF may have a dual role in both modulating the accessibility of the HoxB complex along the axis and in activating the expression of Cdx genes. The position of the shift in RA or FGF responsiveness of Hox genes may be time dependent. Hence, the specific Hox genes in each of these complementary groups may vary in later stages of development or other tissues. These results highlight the key role of Cdx genes in integrating the input of multiple signaling pathways, such as FGFs and RA, in controlling initiation of Hox expression during development and the importance of understanding regulatory events/mechanisms that modulate Cdx expression.

Our understanding of neural codes rests on Shannon's foundations

2019 ◽  
Vol 42 ◽  
Author(s):  
Charles R. Gallistel
Keyword(s):  
Brain Structure ◽  
Neural Tissue ◽  
Neural Codes ◽  
Flow Of Information

Abstract Shannon's theory lays the foundation for understanding the flow of information from world into brain: There must be a set of possible messages. Brain structure determines what they are. Many messages convey quantitative facts (distances, directions, durations, etc.). It is impossible to consider how neural tissue processes these numbers without first considering how it encodes them.

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