title: Bipolar, anastral spindle development in artificially activated sea urchin eggs.
abstract: The mitotic apparatus of the early sea urchin embryo is the archetype example of a centrosome-dominated, large aster spindle organized by means of the centriole of the fertilizing sperm. In this study, we tested the hypothesis that artificially activated sea urchin eggs possess the capacity to assemble the anastral, bipolar spindles present in many acentrosomal systems. Control fertilized Lytechinus pictus embryos and ammonia-activated eggs were immunolabeled for tubulin, centrosomal material, the spindle pole structuring protein NuMA and the mitotic kinesins MKLP1/Kinesin-6, Eg5/Kinesin-5, and KinI/Kinesin-13. Confocal imaging showed that a subset of ammonia-activated eggs contained bipolar "mini-spindles" that were anastral; displayed metaphase and anaphase-like stages; labeled for centrosomal material, NuMA, and the three mitotic kinesins; and were observed in living eggs using polarization optics. These results suggest that spindle structural and motor proteins have the ability to organize bipolar, anastral spindles in sea urchin eggs activated in the absence of the paternal centriole.
authors.affiliation: Department of Biology, Dickinson College, Carlisle, Pennsylvania 17013, USA. henson@dickinson.edu
authors.forename: John H
authors.initials: JH
authors.lastname: Henson
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Fried
authors.forename: Mary K
authors.initials: MK
authors.lastname: McClellan
authors.forename: Jason
authors.initials: J
authors.lastname: Ader
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Davis
authors.forename: Rudolf
authors.initials: R
authors.lastname: Oldenbourg
authors.forename: Calvin R
authors.initials: CR
authors.lastname: Simerly
mesh_terms: D000641:Ammonia / Q000378:metabolism; D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D016764:Cell Polarity; D005260:Female; D005306:Fertilization / Q000502:physiology; D047331:Lytechinus / Q000196:embryology*; D008297:Male; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D008941:Spindle Apparatus / Q000502:physiology / Q000648:ultrastructure
chemical_list: D034961:Antigens, Nuclear; D034521:Nuclear Matrix-Associated Proteins; D000641:Ammonia