Molecular Mechanisms of Tissue Determination and Pattern Formation in Amphibian Embryos

1995 ◽  
Vol 82 (3) ◽  
pp. 123-134 ◽  
Author(s):  
Heinz Tiedemann ◽  
Hildegard Tiedemann ◽  
Horst Grunz ◽  
Walter Kn�chel
Keyword(s):  
Pattern Formation ◽  
Molecular Mechanisms ◽  
Amphibian Embryos

Molecular mechanisms of tissue determination and pattern formation in amphibian embryos

1995 ◽  
Vol 82 (3) ◽  
pp. 123-134 ◽  
Author(s):  
Heinz Tiedemann ◽  
Hildegard Tiedemann ◽  
Horst Grunz ◽  
Walter Kn�chel
Keyword(s):  
Pattern Formation ◽  
Molecular Mechanisms ◽  
Amphibian Embryos

scholarly journals Shh Plays an Inhibitory Role in Cusp Patterning by Regulation of Sostdc1

2018 ◽  
Vol 98 (1) ◽  
pp. 98-106 ◽  
Author(s):  
J. Kim ◽  
Y. Ahn ◽  
D. Adasooriya ◽  
E.J. Woo ◽  
H.J. Kim ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Wnt Signaling ◽  
Molecular Mechanisms ◽  
Wild Type ◽  
Shh Signaling ◽  
Shh Pathway ◽  
Inhibitory Role ◽  
Crown Shape ◽  
Cusp Formation

Crown shapes in mammalian teeth vary considerably from species to species, and morphological characters in crown shape have been used to identify species. Cusp pattern is one of the characters in crown shape. In the processes governing the formation of cusp pattern, the Shh pathway has been implicated as an important player. Suppression of Shh signaling activity in vitro in explant assays appears to induce supernumerary cusp formation in wild-type tooth germs. However, the in vivo role of Shh signaling in cusp pattern formation and the molecular mechanisms by which Shh regulates cusp patterning are not clear. Here, through in vivo phenotypic analyses of mice in which Shh activity was suppressed and compared with wild-type mice, we characterized differences in the location, number, incidence, and shape of supernumerary cusps in molars at embryonic day 15.5. We found that the distances between cusps were reduced in molars of Shh activity–suppressed mice in vivo. These findings confirm and extend the previous idea that Shh acts as an inhibitor in the reaction-diffusion model for cusp pattern formation by negatively regulating the intercuspal distance. We uncovered a significant reduction of expression level of Sostdc1, which encodes a secreted modulator of Wnt signaling, after suppression of Shh activity. The supernumerary cusp formation in Sostdc1−/− mice and compound Sostdc1 and Lrp mutant mice indicates a strong association between Wnt and Shh signaling pathways in cusp patterning. In further support of this idea, there is a high degree of similarity in the supernumerary cusp patterns of mice lacking Sostdc1 or Shh at embryonic day 15.5. These results suggest that Shh plays an inhibitory role in cusp pattern formation by modulating Wnt signaling through the positive regulation of Sostdc1.

scholarly journals Reversal of developmental competence in inverted amphibian eggs

Development ◽  
1983 ◽  
Vol 73 (1) ◽  
pp. 207-220
Author(s):  
Hae Moon Chung ◽  
George M. Malacinski
Keyword(s):  
Pattern Formation ◽  
Early Embryogenesis ◽  
The State ◽  
Developmental Competence ◽  
Cleavage Division ◽  
Developmental Arrest ◽  
Amphibian Embryos

Inverted amphibian embryos were employed for an analysis of pattern formation in early embryogenesis. Axolotl (Ambystoma) and Xenopus eggs were inverted prior to the first cleavage division and permitted to develop upside down to the early gastrulation stage. In both cases the cleavage patterns of the animal and vegetal hemispheres were reversed. By gastrulation, however, developmental arrest began, and no inverted embryos developed beyond neurulation. The state of competence of the animal and vegetal hemisphere cells of inverted embryos was examined in a series of tissue transplantations, usually into genetically marked (albino) hosts. In all cases the developmental competence of the original animal and vegetal hemisphere cells of inverted embryos had been reversed. For example, the egg's original vegetal hemisphere developed into various neural structures. Those observations should eventually be useful in formulating models to account for the mannerin which various regions of the amphibian egg cytoplasm generate early embryonic patterns.

Applications of a Theory of Biological Pattern Formation Based on Lateral Inhibition

1974 ◽  
Vol 15 (2) ◽  
pp. 321-346 ◽  
Author(s):  
H. MEINHARDT ◽  
A. GIERER
Keyword(s):  
Pattern Formation ◽  
Lateral Inhibition ◽  
Molecular Mechanisms ◽  
Positional Information ◽  
Cell Types ◽  
Model Calculations ◽  
Slime Moulds ◽  
Biological Pattern Formation ◽  
Pattern Forming ◽  
Differentiation And Proliferation

Model calculations are presented for various problems of development on the basis of a theory of primary pattern formation which we previously proposed. The theory involves short-range autocatalytic activation and longer-range inhibition (lateral inhibition). When a certain criterion is satisfied, self-regulating patterns are generated. The autocatalytic features of the theory are demonstrated by simulations of the determination of polarity in the Xenopus retina. General conditions for marginal and internal activation, and corresponding effects of symmetry are discussed. Special molecular mechanisms of pattern formation are proposed in which activator is chemically converted into inhibitor, or an activator precursor is depleted by conversion into activator. The (slow) effects of primary patterns on differentiation can be included into the formalism in a straightforward manner. In conjunction with growth, this can lead to asymmetric steady states of cell types, cell differentiation and proliferation as found, for instance, in growing and budding hydra. In 2 dimensions, 2 different types of patterns can be obtained. Under some assumptions, a single pattern-forming system produces a ‘bristle’ type pattern of peaks of activity with rather regular spacings on a surface. Budding of hydra is treated on this basis. If, however, gradients develop under the influence of a weak external or marginal asymmetry, a monotonic gradient can be formed across the entire field, and 2 such gradient-forming systems can specify ‘positional information’ in 2 dimensions. If inhibitor equilibrates slowly, a spatial pattern may oscillate, as observed with regard to the intracellular activation of cellular slime moulds. The applications are intended to demonstrate the ability of the proposed theory to explain properties frequently encountered in developing systems.

A series of novel mutants of Arabidopsis thaliana that are defective in the formation of continuous vascular network: calling the auxin signal flow canalization hypothesis into question

Development ◽  
2000 ◽  
Vol 127 (15) ◽  
pp. 3197-3204 ◽  
Author(s):  
K. Koizumi ◽  
M. Sugiyama ◽  
H. Fukuda
Keyword(s):  
Arabidopsis Thaliana ◽  
Pattern Formation ◽  
Genetic Analysis ◽  
Molecular Mechanisms ◽  
Vascular Tissue ◽  
Early Stage ◽  
Diffusion Reaction ◽  
Signal Flow ◽  
Vein Formation ◽  
Mutant Lines

For the genetic analysis of molecular mechanisms underlying temporal and spatial regulation of vascular pattern formation, we isolated mutants of Arabidopsis thaliana that are impaired in vascular patterning. Microscopic examination of the cotyledonary venation of 3,400 M(3) lines led to the identification of 12 mutant lines. Genetic analysis of 8 of these mutant lines indicated that vein pattern formation in these lines resulted from monogenic recessive mutations in 7 different genes, designated VAN1 through VAN7. Mutations in VAN1 through VAN6 genes caused fragmentation (disconnection or partial loss) of lateral veins of the cotyledon and tertiary veins of the rosette leaf whereas they were less injurious to the formation of major veins. Detailed characterization of the van3 mutant using pAthb8::GUS and pTED3::GUS, as molecular markers for the early stage of vascular tissue formation showed that the provascular tissue of the cotyledonary lateral veins was differentiated in fragments during late embryogenesis. These phenotypes of the van mutants are discussed in relation to the auxin signal flow canalization hypothesis and the diffusion-reaction prepattern hypothesis, with the fragility of the continuity in the minor vein formation favoring the latter hypothesis.

scholarly journals Molecular mechanisms underlying simplification of venation patterns in holometabolous insects

Development ◽  
2020 ◽  
Vol 147 (23) ◽  
pp. dev196394
Author(s):  
Tirtha Das Banerjee ◽  
Antónia Monteiro
Keyword(s):  
Gene Expression ◽  
Pattern Formation ◽  
Molecular Mechanisms ◽  
Positional Information ◽  
Butterfly Species ◽  
Central Research ◽  
Bicyclus Anynana ◽  
Wing Vein ◽  
Text Book ◽  
Research Theme

ABSTRACTHow mechanisms of pattern formation evolve has remained a central research theme in the field of evolutionary and developmental biology. The mechanism of wing vein differentiation in Drosophila is a classic text-book example of pattern formation using a system of positional information, yet very little is known about how species with a different number of veins pattern their wings, and how insect venation patterns evolved. Here, we examine the expression pattern of genes previously implicated in vein differentiation in Drosophila in two butterfly species with more complex venation Bicyclus anynana and Pieris canidia. We also test the function of some of these genes in B. anynana. We identify both conserved as well as new domains of decapentaplegic, engrailed, invected, spalt, optix, wingless, armadillo, blistered and rhomboid gene expression in butterflies, and propose how the simplified venation in Drosophila might have evolved via loss of decapentaplegic, spalt and optix gene expression domains, via silencing of vein-inducing programs at Spalt-expression boundaries, and via changes in expression of vein maintenance genes.

scholarly journals Determination, induction and pattern formation in early amphibian embryos

1996 ◽  
Vol 38 (5) ◽  
pp. 575-575 ◽  
Author(s):  
H. Tiedemann ◽  
M. Asashima ◽  
J. Born ◽  
H. Grunz ◽  
W. Knochel ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Amphibian Embryos
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