title: Central Spindle Self-Organization and Cytokinesis in Artificially Activated Sea Urchin Eggs.
abstract: The ability of microtubules of the mitotic apparatus to control the positioning and initiation of the cleavage furrow during cytokinesis was first established from studies on early echinoderm embryos. However, the identity of the microtubule population that imparts cytokinetic signaling is unclear. The two main--and not necessarily mutually exclusive--candidates are the central spindle and the astral rays. In the present study, we examined cytokinesis in ammonia-activated sea urchin eggs, which lack paternally derived centrosomes and undergo mitosis mediated by unusual anastral, bipolar mini-spindles. Live cell imaging and immunolabeling for microtubules and the centralspindlin constituent and kinesin-related protein, MKLP1, demonstrated that furrowing in ammonia-activated eggs was associated with aligned arrays of centralspindlin-linked, opposed bundles of antiparallel microtubules. These autonomous, zipper-like arrays were not associated with a mitotic apparatus, but did possess characteristics similar to the central spindle region of control, fertilized embryos. Our results highlight the self-organizing nature of the central spindle region and its ability to induce cytokinesis-like furrowing, even in the absence of a complete mitotic apparatus.
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013; Marine Biological Laboratory, Woods Hole, Massachusetts 02543; henson@dickinson.edu.
authors.forename: John H
authors.initials: JH
authors.lastname: Henson
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013;
authors.forename: Mary W
authors.initials: MW
authors.lastname: Buckley
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013;
authors.forename: Mesrob
authors.initials: M
authors.lastname: Yeterian
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013;
authors.forename: Richard M
authors.initials: RM
authors.lastname: Weeks
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213; and.
authors.forename: Calvin R
authors.initials: CR
authors.lastname: Simerly
authors.affiliation: Marine Biological Laboratory, Woods Hole, Massachusetts 02543; Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shuster
mesh_terms: D000818:Animals; D048749:Cytokinesis / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects / Q000502:physiology; D010063:Ovum / Q000166:cytology* / Q000187:drug effects; D012617:Sea Urchins / Q000166:cytology / Q000196:embryology; D008941:Spindle Apparatus / Q000378:metabolism*