Parameters of self-organization in Hydra aggregates.
Self-organization has been demonstrated in a variety of systems ranging from chemical-molecular to ecosystem levels, and evidence is accumulating that it is also fundamental for animal development. Yet, self-organization can be approached experimentally in only a few animal systems. Cells isolated from the simple metazoan Hydra can aggregate and form a complete animal by self-organization. By using this experimental system, we found that clusters of 5-15 epithelial cells are necessary and sufficient to form de novo head-organizing centers in an aggregate. Such organizers presumably arise by a community effect from a small number of cells that express the conserved HyBra1 and HyWnt genes. These local sources then act to pattern and instruct the surrounding cells as well as generate a field of lateral inhibition that ranges up to 1,000 microm. We propose that conserved patterning systems in higher animals originate from extremely robust and flexible molecular self-organizing systems that were selected for during early metazoan evolution.
Technau
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U
Department of Molecular Cell Biology, Darmstadt University of Technology, Schnittspahnstr. 10, 64287 Darmstadt, Germany. technau@bio.tu-darmstadt.de
Cramer von Laue
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C
Rentzsch
F
F
Luft
S
S
Hobmayer
B
B
Bode
H R
HR
Holstein
T W
TW
D000818:Animals; D006829:Hydra / Q000254:growth & development*; D017403:In Situ Hybridization