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Gradual disruption of the actin cytoskeleton induces a series of structural shape changes in cells leading to a transformation of cylindrical cell extensions into a periodic chain of 'pearls.' Quantitative measurements of the pearling instability give a square-root behavior for the wavelength as a function of drug concentration. We present a theory that explains these observations in terms of the interplay between rigidity of the submembranous actin shell and tension that is induced by boundary conditions set by adhesion points. The theory allows estimation of the rigidity and thickness of this supporting shell. The same theoretical considerations explain the shape of nonadherent edges in the general case of untreated cells.

The Rho family of GTPases help regulate the actin cytoskeleton, cell adhesion, smooth muscle contraction, neurite retraction, and cytokinesis. However, the precise molecular mechanisms by which these proteins operate is not fully understood.

Two mutant alpha subunit genes of the position-specific 2 (PS2) integrins were developed to determine whether the function PS2 is regulated during embryonic development. The entire cytoplasmic domain was removed in one mutants, while the alpha(sub PS2) variant form was deleted from the other. Results showed that the removal of the alpha(sub PS2) cytoplasmic domain promotes formation of PS2 integrin that mediates development of an abnormal size and number of muscle attachments. This indicates that modulation of integrin function is essential for embryonic morphogenesis.