Models for the generation of the embryonic body axes: ontogenetic and evolutionary aspects

Meinhardt, Hans

doi:10.1016/j.gde.2004.06.012

Cited by 20 publications

(12 citation statements)

References 67 publications

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“…The identification of secreted proteins with morphogenic activity in a variety of regenerating systems supports the notion that cell-cell communication influences tissue patterning during regeneration (3)(4)(5)(6)(7)(8). Theoretical models have suggested that intrinsic properties of morphogen gradients might be sufficient to account for the reestablishment of complete pattern from tissue fragments during embryonic development or in regeneration (9)(10)(11)(12). However, few experimental systems have enabled the study of this problem in regenerating animals.…”

mentioning

confidence: 70%

“…In Xenopus, this attribute involves rescaling of a signaling network with ventrally expressed BMP2/4/7 and dorsally expressed ADMP ligands (37). Theoretical models of regulative development in Xenopus embryos (10) and other systems (9,12) suggest that intrinsic properties of the diffusion, degradation, shuttling, and interaction of protein gradients could be sufficient to account for self-regulation to restore missing pattern elements or tissue. However, the molecular mechanisms controlling the property of self-regulation in regeneration are not well understood.…”

Section: Discussionmentioning

confidence: 99%

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A wound-induced Wnt expression program controls planarian regeneration polarity

Petersen

Reddien

2009

Proc. Natl. Acad. Sci. U.S.A.

227

334

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Regeneration requires specification of the identity of new tissues to be made. Whether this process relies only on intrinsic regulative properties of regenerating tissues or whether wound signaling provides input into tissue repatterning is not known. The headversus-tail regeneration polarity decision in planarians, which requires Wnt signaling, provides a paradigm to study the process of tissue identity specification during regeneration. The SmedwntP-1 gene is required for regeneration polarity and is expressed at the posterior pole of intact animals. Surprisingly, wntP-1 was expressed at both anterior-and posterior-facing wounds rapidly after wounding. wntP-1 expression was induced by all types of wounds examined, regardless of whether wounding prompted tail regeneration. Regeneration polarity was found to require new expression of wntP-1. Inhibition of the wntP-2 gene enhanced the polarity phenotype due to wntP-1 inhibition, with new expression of wntP-2 in regeneration occurring subsequent to expression of wntP-1 and localized only to posterior-facing wounds. New expression of wntP-2 required wound-induced wntP-1. Finally, wntP-1 and wntP-2 expression changes occurred even in the absence of neoblast stem cells, which are required for regeneration, suggesting that the role of these genes in polarity is independent of and instructive for tail formation. These data indicate that wound-induced input is involved in resetting the normal polarized features of the body axis during regeneration.anteroposterior axis ͉ ␤-catenin ͉ planaria

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mentioning

confidence: 70%

Section: Discussionmentioning

confidence: 99%

A wound-induced Wnt expression program controls planarian regeneration polarity

Petersen

Reddien

2009

Proc. Natl. Acad. Sci. U.S.A.

227

334

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“…In cnidarians and bilaterians, Wnt genes are expressed in the blastopore and equivalent regions, and this localized Wnt expression is critical for organizing the primary body axis (1)(2)(3). Polarized Wnt expression in the sponge Amphimedon embryo (4) provides evidence that the origin of the Wnt signaling center is at the base of metazoan evolution.…”

mentioning

confidence: 99%

“…It has been hypothesized that the organizer patterns the body along the oral-aboral axis through diffusible short-range autocatalytic activators and longrange inhibitors (12,13). Although the molecular identity of these theoretical factors is still uncertain, Wnt/β-catenin signaling has been postulated to encompass the activator (3).…”

mentioning

confidence: 99%

“…Indeed, elevated activation of Wnt/β-catenin signal induces ectopic HyWnt3 expression (6), and autoregulation through the Wnt/β-catenin circuit has been proposed to activate and maintain HyWnt3 expression (6), although a direct molecular evidence is missing. A simple autoregulation although cannot explain the restriction of HyWnt3 expression to the head organizer, as HyTcf and Hyβ-catenin are broadly expressed and seem to be required for the narrower HyWnt3 expression (3,5,15). Thus, the mechanism for HyWnt3 regulation remains to be discovered.…”

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confidence: 99%

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Autoregulatory and repressive inputs localize Hydra Wnt3 to the head organizer

Nakamura

Tsiairis

Özbek

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

126

177

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Polarized Wnt signaling along the primary body axis is a conserved property of axial patterning in bilaterians and prebilaterians, and depends on localized sources of Wnt ligands. However, the mechanisms governing the localized Wnt expression that emerged early in evolution are poorly understood. Here we find in the cnidarian Hydra that two functionally distinct cis-regulatory elements control the head organizer-associated Hydra Wnt3 (HyWnt3). An autoregulatory element, which mediates direct inputs of Wnt/ β-catenin signaling, highly activates HyWnt3 transcription in the head region. In contrast, a repressor element is necessary and sufficient to restrict the activity of the autoregulatory element, thereby allowing the organizer-specific expression. Our results reveal that a combination of autoregulation and repression is crucial for establishing a Wnt-expressing organizing center in a basal metazoan. We suggest that this transcriptional control is an evolutionarily old strategy in the formation of Wnt signaling centers and metazoan axial patterning.regulatory DNAs | cis-regulation | enhancer | molecular evolution | axis formation

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Head Induction

Kiecker¹

2005

Cell Signaling and Growth Factors in Development

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Models for the generation of the embryonic body axes: ontogenetic and evolutionary aspects

Cited by 20 publications

References 67 publications

A wound-induced Wnt expression program controls planarian regeneration polarity

A wound-induced Wnt expression program controls planarian regeneration polarity

Autoregulatory and repressive inputs localize Hydra Wnt3 to the head organizer

Head Induction

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