Accumulation of WGA Receptors in the Cleavage Furrow during Cytokinesis of Sea Urchin Eggs |
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Authors: | Tomoyoshi Yoshigaki |
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Affiliation: | Department of Biology, College of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153, Japan |
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Abstract: | Sea urchin eggs stained with fluorescein-conjugated wheat germ agglutinin (F-WGA) before or after fixation showed a marked accumulation of fluorescence at the cleavage furrow in the first and the second cell divisions. WGA receptors (WGA-binding membrane glycoproteins) were redistributed to the equatorial region through several steps in compressed eggs. Accumulated WGA receptors showed a distribution similar to that of contractile-ring microfilaments throughout most of the steps. Therefore, the former is probably associated with the latter directly or indirectly. Labeling with F-WGA provides a simple method to detect contractile-ring microfilaments in living eggs. Treatment of eggs with colcemid shortly before cytokinesis dispersed the ring-like accumulation of WGA receptors together with contractile-ring microfilaments. This result suggests that microtubule structures, probably asters, are involved in the redistribution of WGA receptors. Cytochalasin B prevented furrowing when it was applied shortly before cytokinesis. While contractile-ring microfilaments showed a spotty distribution in the expected furrow region, WGA receptors were normally redistributed. Furthermore, a higher concentration of the drug allowed the appearance of accumulated WGA receptors in compressed eggs although the development into a ring-like configuration was inhibited. These observations suggest the possibility that the redistribution of WGA receptors is involved in the formation of contractile ring. |
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