Cell polarity: intrinsic or externally imposed?
A basic question in studies of the genesis of cell polarity is whether the polarity is an intrinsic and permanent property of cells or whether it is externally imposed by signals at the cell periphery. Current models favor the possibility that an external signal selectively imposes a polarized cell morphology. However, recent data from different experimental systems are discussed here that support the idea that an intrinsic polarity in animal cells is maintained through a dynamic process involving specific activities of the cortical microfilament system and the centrosome-microtubule complex. In this view, external signals capable of modulating cell polarity, for example, during chemotaxis or histogenesis, do so by acting on mechanisms that maintain cells permanently polarized. The contribution of the cytoskeleton to the genesis of cell polarity is discussed, with particular reference to experimental evidence for global cytoskeletal dynamics, and it is suggested that critical advances in our understanding of the maintenance of cell polarity will depend on our obtaining further knowledge of the molecular mechanisms controlling interactions between microtubules and microfilaments. Microtubules appear to exert an inhibitory control on the recruitment of cytoplasmic myosin into the cortex, and there are data indicating that the centrosome and centrioles could actively contribute to the establishment of cell polarity.
Bornens
M
M
Centre de Genetique Moléculaire, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
D008841:Actin Cytoskeleton / Q000502:physiology; D000199:Actins / Q000502:physiology; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002468:Cell Physiological Phenomena; D002477:Cells / Q000648:ultrastructure; D003599:Cytoskeleton / Q000502:physiology; D008870:Microtubules / Q000502:physiology; D008954:Models, Biological
D000199:Actins