Positional information and pattern formation in Hydra. Dynamics of regions away from the boundary

Development ◽  
1975 ◽  
Vol 33 (2) ◽  
pp. 511-521
Author(s):  
J. Hicklin ◽  
A. Hornbruch ◽  
L. Wolpert
Keyword(s):  
Pattern Formation ◽  
Positional Information ◽  
Polarity Reversal ◽  
Type Model ◽  
Gradient Type ◽  
Positional Value

The dynamics of regions away from the head-end boundary have been investigated by avariety of assays, and the changes appear to be slow. If, for example, a head end is graftedonto a peduncle to give H/56F, region 5 does not become a region 1 within 72 h. Suchresults support a gradient type model, and exclude a head end inducing a region 1 in thetissue adjacent to it. The changes can be interpreted if the positional value were effectivelyslowly diffusible: about 10 times more slowly than the positional signal. These results alsohave implications for studies on polarity reversal.

Growth factors and pattern formation

Development ◽  
1981 ◽  
Vol 65 (Supplement) ◽  
pp. 187-207
Author(s):  
J. C. Smith
Keyword(s):  
Cell Cycle ◽  
Growth Factors ◽  
Pattern Formation ◽  
Positional Information ◽  
In Vitro Assay ◽  
Vitro Assay ◽  
Produce Cell ◽  
Morphogenetic Factors ◽  
Positional Value

Growth and pattern formation occur simultaneously in many epimorphic fields and it has been suggested that specification of positional information is somehow linked to cell division. It is possible, therefore, that boundary regions responsible for the specification of positional information produce cell growth factors. In this paper I review the properties of some known growth factors, describe their effects on the cell cycle and discuss how they might act. In developing a convenient in vitro assay for morphogenetic factors it will be much easier to measure incorporation of [3H]thymidine into responding cells than to estimate changes in positional value.

scholarly journals Biological notion of positional information/value in morphogenesis theory

2020 ◽  
Vol 64 (10-11-12) ◽  
pp. 453-463
Author(s):  
Yue Wang ◽  
Jérémie Kropp ◽  
Nadya Morozova
Keyword(s):  
Pattern Formation ◽  
Molecular Mechanisms ◽  
Positional Information ◽  
Theoretical Models ◽  
Cell Development ◽  
Information Value ◽  
Morphogen Gradients ◽  
Cell Position ◽  
Positional Value

The notions of positional information and positional value describe the role of cell position in cell development and pattern formation. Despite their frequent usage in literature, their definitions are blurry, and are interpreted differently by different researchers. Through reflection on previous definitions and usage, and analysis of related experiments, we propose three clear and verifiable criteria for positional information/value. Then we reviewed literature on molecular mechanisms of cell development and pattern formation, to search for a possible molecular basis of positional information/value, including those used in theoretical models. We conclude that although morphogen gradients and cell-to-cell contacts are involved in the pattern formation process, complete molecular explanations of positional information/value are still far from reality.

Interaction between the proximo-distal and antero-posterior co-ordinates of positional value during the specification of positional information in the early development of the chick limb-bud

Development ◽  
1974 ◽  
Vol 32 (1) ◽  
pp. 227-237
Author(s):  
Dennis Summerbell
Keyword(s):  
Early Development ◽  
Anterior Margin ◽  
Positional Information ◽  
Apical Ectodermal Ridge ◽  
Limb Bud ◽  
Anteroposterior Axis ◽  
Zone Of Polarizing Activity ◽  
Positional Value ◽  
Special Region

The experiments examine the extent of reduplication of skeletal parts across the anteroposterior axis, following the transplantation of a zone of polarizing activity (ZPA) to the anterior margin of the limb-bud at successively later stages. Previous studies have suggested that the function of the apical ectodermal ridge (AER) is to maintain cells in a special region at the distal tip (the progress zone) labile, with respect to their positional value along the proximo-distal axis. Similarly, the results of these experiments demonstrate that cells in the progress zone are able to change their antero-posterior positional value under the influence of the grafted ZPA, while cells at more proximal levels remain unaffected. In turn, the ZPA may effect the activity of the AER and hence the progress zone.

Receptor-Based Models with Diffusion-Driven Instability for Pattern Formation in Hydra

2003 ◽  
Vol 11 (03) ◽  
pp. 293-324 ◽  
Author(s):  
Anna Marciniak-Czochra
Keyword(s):  
Pattern Formation ◽  
Feedback Loop ◽  
De Novo ◽  
Initial Conditions ◽  
Reaction Diffusion ◽  
Reaction Diffusion Equations ◽  
Variable Model ◽  
Dissociated Cells ◽  
Cutting Experiments ◽  
Positional Value

The aim of this paper is to show under which conditions a receptor-based model can produce and regulate patterns. Such model is applied to the pattern formation and regulation in a fresh water polyp, hydra. The model is based on the idea that both head and foot formation could be controlled by receptor-ligand binding. Positional value is determined by the density of bound receptors. The model is defined in the form of reaction-diffusion equations coupled with ordinary differential equations. The objective is to check what minimal processes are sufficient to produce patterns in the framework of a diffusion-driven (Turing-type) instability. Three-variable (describing the dynamics of ligands, free and bound receptors) and four-variable models (including also an enzyme cleaving the ligand) are analyzed and compared. The minimal three-variable model takes into consideration the density of free receptors, bound receptors and ligands. In such model patterns can evolve only if self-enhancement of free receptors, i.e., a positive feedback loop between the production of new free receptors and their present density, is assumed. The final pattern strongly depends on initial conditions. In the four-variable model a diffusion-driven instability occurs without the assumption that free receptors stimulate their own synthesis. It is shown that gradient in the density of bound receptors occurs if there is also a second diffusible substance, an enzyme, which degrades ligands. Numerical simulations are done to illustrate the analysis. The four-variable model is able to capture some results from cutting experiments and reflects de novo pattern formation from dissociated cells.

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.

Positional information and pattern regulation in hydra: the formation of boundary regions following axial grafts

Development ◽  
1973 ◽  
Vol 30 (3) ◽  
pp. 701-725
Author(s):  
J. Hicklin ◽  
A. Hornbruch ◽  
L. Wolpert ◽  
M. Clarke
Keyword(s):  
Computer Simulations ◽  
Positional Information ◽  
The Other ◽  
Simple Computer ◽  
Gradient Model ◽  
Set Up ◽  
Pattern Regulation ◽  
Positional Value ◽  
Threshold Amount

A two-gradient model is proposed for regulation and regeneration of the head end of hydra in terms of positional information. One gradient is set up by a diffusible substance made at the head end, which may be regarded as a positional signal, and the other is a more stable cellular parameter which is the positional value. The rule for head end formation is that the concentration of the diffusible substance falls a threshold amount below the positional value. A variety of instantaneous axial grafts have been carried out which are discussed in terms of this model. Some simple computer simulations of diffusion are provided. There is some evidence that the source of the positional signal is localized at the head end. Some experiments on changes in polarity are given. It also seems that the positional signal from the head end inhibits foot end formation.

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