Effects of the phosphatase inhibitors, okadaic acid, ATPγS, and calyculin A on the dividing sand dollar egg

Yukihisa Hamaguchi, Ryoko Kuriyama

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


The effects of the phosphatase inhibitors, okadaic acid (OA), adenosine 5′-O-(3-thiotriphosphate) (ATPγS), and calyculin A (CL-A) on anaphase chromosome movement, cytokinesis, and cytoskeletal structures at cell division were examined by being microinjected into mitotic sand dollar eggs. When OA was injected, chromosome movement was inhibited and, moreover, chromosomes were ejected from the polar regions of the mitotic apparatus. By immunofluorescence, microtubules were observed to be severed in the OA-injected eggs, causing the smooth cell surface to be changed to an irregular surface. When ATPγS and CL-A were injected, the effect on cell shape was remarkable: In dividing eggs, furrowing stopped within several seconds after injection, small blebs appeared on the cell surface and became large, spherical or dumbbell cell shapes then changed to irregular forms, and subsequently cytoplasmic flow occurred. Microfilament detection revealed that actin accumulation in the cortex, which was not limited to the furrow cortex, occurred shortly after injection. Cortical accumulation of actin is thought to induce force generation and random cortical contraction, and accordingly to result in bleb extrusion from the cortex. Consequently, the phosphatase inhibitors inhibited the transition from mitosis to interphase by mediating cortical accumulation of actin filaments and/or fragmentation of microtubules.

Original languageEnglish (US)
Pages (from-to)127-137
Number of pages11
JournalCell Structure and Function
Issue number3
StatePublished - Jun 2002


  • Actin
  • Chromosome movement
  • Cleavage furrow
  • Microtubule
  • Phosphatase inhibitor
  • Sand dollar egg

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