title: Evolutionary comparisons reveal a positional switch for spindle pole oscillations in Caenorhabditis embryos.
abstract: During the first embryonic division in Caenorhabditis elegans, the mitotic spindle is pulled toward the posterior pole of the cell and undergoes vigorous transverse oscillations. We identified variations in spindle trajectories by analyzing the outwardly similar one-cell stage embryo of its close relative Caenorhabditis briggsae. Compared with C. elegans, C. briggsae embryos exhibit an anterior shifting of nuclei in prophase and reduced anaphase spindle oscillations. By combining physical perturbations and mutant analysis in both species, we show that differences can be explained by interspecies changes in the regulation of the cortical Gα-GPR-LIN-5 complex. However, we found that in both species (1) a conserved positional switch controls the onset of spindle oscillations, (2) GPR posterior localization may set this positional switch, and (3) the maximum amplitude of spindle oscillations is determined by the time spent in the oscillating phase. By investigating microevolution of a subcellular process, we identify new mechanisms that are instrumental to decipher spindle positioning.
authors.affiliation: Laboratory of Molecular Biology of the Cell, UMR5239, Ecole Normale Supérieure de Lyon, Centre National de la Recherche Scientifique, 69007 Lyon, France.
authors.forename: Soizic
authors.initials: S
authors.lastname: Riche
authors.forename: Melissa
authors.initials: M
authors.lastname: Zouak
authors.forename: Françoise
authors.initials: F
authors.lastname: Argoul
authors.forename: Alain
authors.initials: A
authors.lastname: Arneodo
authors.forename: Jacques
authors.initials: J
authors.lastname: Pecreaux
authors.forename: Marie
authors.initials: M
authors.lastname: Delattre
mesh_terms: D000818:Animals; D005075:Biological Evolution; D002107:Caenorhabditis / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000378:metabolism / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D016764:Cell Polarity; D004625:Embryo, Nonmammalian / Q000166:cytology*; D008941:Spindle Apparatus / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; C475459:G protein regulator 2, C elegans