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Séminaires MSC
"Matière et Systèmes Complexes"

                      
Lundi 18 avril 2005 à 11h30
Tour 33, couloir 33-43, 2ème étage, salle de réunion

Malcolm S. Steinberg
(Princeton University)

  Specifying Embryonic Self-Assembly Through Cell-Cell Adhesion: From Anatomy to Thermodynamics

During embryonic development, sheets of tissue flow, one over another, and segregate from each other as they differentiate into the body's various tissues and organs.  In the 1960s we conducted behavioral analyses demonstrating that these rearrangements of tissues mimic, in detail, those of mutually immiscible liquids, whose molecules interact with different energies and rearrange to minimize global binding free energy. This requires that, of two mutually immiscible liquids, the one of lower surface tension must tend to spread over its partner. Our "Differential Adhesion Hypothesis" proposed that the motile and mutually adhesive cells of "liquid tissues" do the same, intercellular adhesions playing the same role in liquid tissues that intermolecular attractions play in non-living liquids.
We have measured the surface tensions of a number of embryonic tissues and shown that they accurately predict the self-assembly behavior of these tissues and their component cells. In cell lines genetically engineered to express specific adhesion molecules (cadherins) in measured quantities, we show that cell aggregate surface tension is a linear reflection of cadherin expression level.  We conclude that cell-cell adhesiveness is the underlying determinant of the liquidlike self-assembly behavior of embryonic cells