Abstract
Publisher Summary This chapter describes the different aspects of actin gelation in sea urchin egg extracts. Sea urchin eggs are not usually considered to be highly motile cells, and they do display a striking extension of microvilli following fertilization and classical material for studying cell division. Eggs were obtained from the Hawaiian sea urchin Tripneustes grutillu by injection of isotonic KCI into the body cavity. The jelly coat was removed by rapidly titrating a 10% egg suspension to pH 5 with HCl, then washing the eggs several times with Millipore-filtered seawater. The eggs were sedimented by hand centrifugation and the packed egg volume estimated. The formation of a structured actin gel consisting of linear aggregates of actin filaments can be induced by warming the cytoplasmic extracts. Actin has been isolated from acetone powders of sea urchin eggs and partially characterized. The procedure depends on the ability of this invertebrate actin to form large bundles in the presence of high salt and appears to be generally applicable to echinoderms. It is suggested that fascin functions in sea urchin eggs and other cells to organize actin filaments into the bundles that form the cores of filopodia and microvilli. A type of phagocytic coelomocyte from sea urchins was used to study the role of this actin-cross-linking protein.
Published Version
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