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Curr Biol. 2012 Jun 5;22(11):R458-66. doi: 10.1016/j.cub.2012.03.045.

Bistability, bifurcations, and Waddington's epigenetic landscape.

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  • 1Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305-5174, USA.

Abstract

Waddington's epigenetic landscape is probably the most famous and most powerful metaphor in developmental biology. Cells, represented by balls, roll downhill through a landscape of bifurcating valleys. Each new valley represents a possible cell fate and the ridges between the valleys maintain the cell fate once it has been chosen. Here I examine models of two important developmental processes - cell-fate induction and lateral inhibition - and ask whether the landscapes for these models at least qualitatively resemble Waddington's picture. For cell-fate induction, the answer is no. The commitment of a cell to a new fate corresponds to the disappearance of a valley from the landscape, not the splitting of one valley into two, and it occurs through a type of bifurcation - a saddle-node bifurcation - that possesses an intrinsic irreversibility that is missing from Waddington's picture. Lateral inhibition, a symmetrical cell-cell competition process, corresponds better to Waddington's picture, with one valley reversibly splitting into two through a pitchfork bifurcation. I propose an alternative epigenetic landscape that has numerous valleys and ridges right from the start, with the process of cell-fate commitment corresponding to the irreversible disappearance of some of these valleys and ridges, via cell-fate induction, complemented by the creation of new valleys and ridges through processes like cell-cell competition.

PMID:
22677291
PMCID:
PMC3372930
DOI:
10.1016/j.cub.2012.03.045
[PubMed - indexed for MEDLINE]
Free PMC Article
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