Pearling in cells: A clue to understanding cell shape

Gradual disruption of the actin cytoskeleton induces a series of structural shape changes in cells leading to a transformation of cylindrical cell ext ensions into a periodic chain of "pearls." Quantitative measurements of the pearling instability give a square-root behavior for the wavelength as a f unction of drug concentration, We present a theory that explains these obse rvations in terms of the interplay between rigidity of the submembranous ac tin shell and tension that is induced by boundary conditions set by adhesio n points. The theory allows estimation of the rigidity and thickness of thi s supporting shell. The same theoretical considerations explain the shape o f nonadherent edges in the general case of untreated cells.