Cell surface and cytokinetic structures in cell shape determination of mouse fibroblasts. Events involved in cell rounding induced by removal of loosely bound macromolecular moieties from the cell surface.

Cell rounding was induced in synchronised mouse embryo fibroblasts without the use of drugs by a new method based on removal from the cell surface of loosely bound macromolecular moieties. The cells were examined by scanning and transmission electron microscopy and also by specific fluorescence methods during experimentally induced progression from the spread to a rounded form to assess changes in the cell surface and in the arrangement of cytoskeletal elements. Early events were a loss of order in the subcortical microfilament network and the formation of surface blebs. This was followed by disintegration of stress fibres and body retraction. Microtubules and intermediate filaments maintained their integrity but moved inwards towards the rounded perinuclear part of the cells. The relationship between surface alterations, organisation of the cytoskeleton and cell conformation is discussed.