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Microtubules are the only structural constituent of the spindle apparatus required for induction of cell cleavage.

Alsop GB, Zhang D - J. Cell Biol. (2003)

Bottom Line: We show that furrow induction occurs under all circumstances, so long as sufficient microtubules are present.Microtubules, as the only spindle structural constituent, undergo dramatic, stage-specific reorganizations, radiating toward cell cortex in "metaphase," disassembling in "anaphase," and bundling into arrays in "telophase." Furrow induction usually occurs at multisites around microtubule bundles, but only those induced by sustained bundles ingress.We suggest that microtubules, regardless of source, are the only structural constituent of the spindle apparatus essential for cleavage furrow induction.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA.

ABSTRACT
Structural constituents of the spindle apparatus essential for cleavage induction remain undefined. Findings from various cell types using different approaches suggest the importance of all structural constituents, including asters, the central spindle, and chromosomes. In this study, we systematically dissected the role of each constituent in cleavage induction in grasshopper spermatocytes and narrowed the essential one down to bundled microtubules. Using micromanipulation, we produced "cells" containing only asters, a truncated central spindle lacking both asters and chromosomes, or microtubules alone. We show that furrow induction occurs under all circumstances, so long as sufficient microtubules are present. Microtubules, as the only spindle structural constituent, undergo dramatic, stage-specific reorganizations, radiating toward cell cortex in "metaphase," disassembling in "anaphase," and bundling into arrays in "telophase." Furrow induction usually occurs at multisites around microtubule bundles, but only those induced by sustained bundles ingress. We suggest that microtubules, regardless of source, are the only structural constituent of the spindle apparatus essential for cleavage furrow induction.

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Furrow abscission and regression in micromanipulated cells. Unless indicated, time is given in minutes. (A) An aster-containing pocket, produced as in Fig. 1, undergoes successful furrow initiation (0–68 min, arrows) and ingression (88), but fails in abscission due to furrow regression (16 h). (B) A cell lacking both asters and pronuclei, manipulated as in Fig. 2, is fully capable of furrow induction (12–45, arrows), ingression (72), and normal abscission (17.1 h; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). (B') Rhodamine dextran microinjected into one daughter cell gradually flows into the other in both visually abscised experimental cells (aster removal, 17.3–17.8 h after cleavage initiation) and nonmanipulated controls (control, 17.2–17.7 h after cleavage initiation). (C) Despite normal furrow induction and ingression (155–243, arrows), cells containing only microtubules, manipulated as in Fig. 3, usually fail to separate (315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). An exception is shown in Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1. Bars, 10 μm.
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fig5: Furrow abscission and regression in micromanipulated cells. Unless indicated, time is given in minutes. (A) An aster-containing pocket, produced as in Fig. 1, undergoes successful furrow initiation (0–68 min, arrows) and ingression (88), but fails in abscission due to furrow regression (16 h). (B) A cell lacking both asters and pronuclei, manipulated as in Fig. 2, is fully capable of furrow induction (12–45, arrows), ingression (72), and normal abscission (17.1 h; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). (B') Rhodamine dextran microinjected into one daughter cell gradually flows into the other in both visually abscised experimental cells (aster removal, 17.3–17.8 h after cleavage initiation) and nonmanipulated controls (control, 17.2–17.7 h after cleavage initiation). (C) Despite normal furrow induction and ingression (155–243, arrows), cells containing only microtubules, manipulated as in Fig. 3, usually fail to separate (315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). An exception is shown in Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1. Bars, 10 μm.

Mentions: In cells containing asters (Fig. 5 A, 0, *) alone, furrow ingression (68, arrows) tightly constricts the bundled microtubule array (88). Surprisingly, despite the presence of centrosomes, such furrows (n = 5) eventually regress (Fig. 5 A, 16 h). In contrast, furrow ingression (Fig. 5 B, 12–72, arrows; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1) in cells (n = 11) lacking asters and pronuclei sustains and leads to midbody abscission, yielding two daughter cells (17.1 h). Owing to observations that grasshopper spermatocytes remain connected after cytokinesis (Carlson and Handel, 1988) and cell cleavage regresses in C. elegans Zen-4 mutants even after daughter cells enter G1 phase (Severson et al., 2000), we compared visually abscised experimental cells (n = 5) with nonmanipulated controls (n = 5). In both cases, injection of rhodamine dextran (Bukauskas et al., 1992) into one daughter cell results in accumulation of fluorescence in the other (Fig. 5 B'), showing that micromanipulation does not alter the final stage of cell cleavage. When microtubules are the only remaining spindle constituent (n = 6; Fig. 5 C), furrow ingression (155–243, arrows) is usually followed by regression (Fig. 5 C, 315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1), except in one cell where successful abscission is observed (see Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1; Video 5).


Microtubules are the only structural constituent of the spindle apparatus required for induction of cell cleavage.

Alsop GB, Zhang D - J. Cell Biol. (2003)

Furrow abscission and regression in micromanipulated cells. Unless indicated, time is given in minutes. (A) An aster-containing pocket, produced as in Fig. 1, undergoes successful furrow initiation (0–68 min, arrows) and ingression (88), but fails in abscission due to furrow regression (16 h). (B) A cell lacking both asters and pronuclei, manipulated as in Fig. 2, is fully capable of furrow induction (12–45, arrows), ingression (72), and normal abscission (17.1 h; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). (B') Rhodamine dextran microinjected into one daughter cell gradually flows into the other in both visually abscised experimental cells (aster removal, 17.3–17.8 h after cleavage initiation) and nonmanipulated controls (control, 17.2–17.7 h after cleavage initiation). (C) Despite normal furrow induction and ingression (155–243, arrows), cells containing only microtubules, manipulated as in Fig. 3, usually fail to separate (315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). An exception is shown in Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1. Bars, 10 μm.
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fig5: Furrow abscission and regression in micromanipulated cells. Unless indicated, time is given in minutes. (A) An aster-containing pocket, produced as in Fig. 1, undergoes successful furrow initiation (0–68 min, arrows) and ingression (88), but fails in abscission due to furrow regression (16 h). (B) A cell lacking both asters and pronuclei, manipulated as in Fig. 2, is fully capable of furrow induction (12–45, arrows), ingression (72), and normal abscission (17.1 h; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). (B') Rhodamine dextran microinjected into one daughter cell gradually flows into the other in both visually abscised experimental cells (aster removal, 17.3–17.8 h after cleavage initiation) and nonmanipulated controls (control, 17.2–17.7 h after cleavage initiation). (C) Despite normal furrow induction and ingression (155–243, arrows), cells containing only microtubules, manipulated as in Fig. 3, usually fail to separate (315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1). An exception is shown in Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1. Bars, 10 μm.
Mentions: In cells containing asters (Fig. 5 A, 0, *) alone, furrow ingression (68, arrows) tightly constricts the bundled microtubule array (88). Surprisingly, despite the presence of centrosomes, such furrows (n = 5) eventually regress (Fig. 5 A, 16 h). In contrast, furrow ingression (Fig. 5 B, 12–72, arrows; see Video 4, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1) in cells (n = 11) lacking asters and pronuclei sustains and leads to midbody abscission, yielding two daughter cells (17.1 h). Owing to observations that grasshopper spermatocytes remain connected after cytokinesis (Carlson and Handel, 1988) and cell cleavage regresses in C. elegans Zen-4 mutants even after daughter cells enter G1 phase (Severson et al., 2000), we compared visually abscised experimental cells (n = 5) with nonmanipulated controls (n = 5). In both cases, injection of rhodamine dextran (Bukauskas et al., 1992) into one daughter cell results in accumulation of fluorescence in the other (Fig. 5 B'), showing that micromanipulation does not alter the final stage of cell cleavage. When microtubules are the only remaining spindle constituent (n = 6; Fig. 5 C), furrow ingression (155–243, arrows) is usually followed by regression (Fig. 5 C, 315–390, arrow; see Video 5, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1), except in one cell where successful abscission is observed (see Fig. S2, available at http://www.jcb.org/cgi/content/full/jcb.200301073/DC1; Video 5).

Bottom Line: We show that furrow induction occurs under all circumstances, so long as sufficient microtubules are present.Microtubules, as the only spindle structural constituent, undergo dramatic, stage-specific reorganizations, radiating toward cell cortex in "metaphase," disassembling in "anaphase," and bundling into arrays in "telophase." Furrow induction usually occurs at multisites around microtubule bundles, but only those induced by sustained bundles ingress.We suggest that microtubules, regardless of source, are the only structural constituent of the spindle apparatus essential for cleavage furrow induction.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, Oregon State University, 3029 Cordley Hall, Corvallis, OR 97331, USA.

ABSTRACT
Structural constituents of the spindle apparatus essential for cleavage induction remain undefined. Findings from various cell types using different approaches suggest the importance of all structural constituents, including asters, the central spindle, and chromosomes. In this study, we systematically dissected the role of each constituent in cleavage induction in grasshopper spermatocytes and narrowed the essential one down to bundled microtubules. Using micromanipulation, we produced "cells" containing only asters, a truncated central spindle lacking both asters and chromosomes, or microtubules alone. We show that furrow induction occurs under all circumstances, so long as sufficient microtubules are present. Microtubules, as the only spindle structural constituent, undergo dramatic, stage-specific reorganizations, radiating toward cell cortex in "metaphase," disassembling in "anaphase," and bundling into arrays in "telophase." Furrow induction usually occurs at multisites around microtubule bundles, but only those induced by sustained bundles ingress. We suggest that microtubules, regardless of source, are the only structural constituent of the spindle apparatus essential for cleavage furrow induction.

Show MeSH
Related in: MedlinePlus