Schedule May 27, 2011
Polarity Patterns of Stress Fibers
Philippe Marcq (Institut Curie)

Stress fibers are bundles of actin filaments made contractile by interaction with myosin minifilaments, and elastic by crosslinking with alpha-actinin and other proteins. The spatial profile of the polarity of the actin filaments inside contractile actomyosin bundles is known to be either monotonic (graded) or periodic (alternating) . In the framework of linear irreversible thermodynamics, we write the constitutive equations for a one-dimensional, polar, active elastomer and show that the transition from graded to alternating polarity patterns is a nonequilibrium Lifshitz point, where a diffusion constant changes sign. Active contractility is a necessary condition for the emergence of sarcomeric, alternating polarity patterns.

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