title: Relative changes in F-actin during the first cell cycle: evidence for two distinct pools of F-actin in the sea urchin egg.
abstract: The cortical actin cytoskeleton undergoes dramatic rearrangements during fertilization of sea urchin eggs. To characterize these changes further, we quantified the relative changes in filamentous actin (F-actin) during fertilization and the first cell cycle in both intact eggs and in isolated cortices by quantitative fluorescence microscopy. The level of F-actin in the intact egg decreased after fertilization and continued to decrease throughout the first cell cycle. By 60 min after fertilization, the level of F-actin had decreased to 50% of the unfertilized sea urchin egg. By cytokinesis, the level of F-actin had decreased to 30% of the unfertilized egg. After completion of cell division, individual blastomeres had 10% of the F-actin in the unfertilized egg. In contrast, there was an increase in cortical F-actin to 370% of the level in the unfertilized egg after fertilization. This increase corresponded to the formation of microvilli. There was little change in the level of cortical F-actin during the first cell cycle. We draw parallels to other systems that increase the amount of F-actin in the Triton-insoluble cytoskeleton by recruiting actin from a Triton-soluble pool of F-actin.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, Indiana, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Heil-Chapdelaine
authors.forename: J J
authors.initials: JJ
authors.lastname: Otto
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D005306:Fertilization / Q000502:physiology*; D005456:Fluorescent Dyes; D008856:Microscopy, Fluorescence; D018375:Neutrophil Activation; D010063:Ovum; D010590:Phalloidine; D012235:Rhodamines; D012617:Sea Urchins
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; D012235:Rhodamines; D010590:Phalloidine