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1.
Mol Biol Cell ; 26(11): 2020-9, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25833711

RESUMO

During mitosis, chromosomes are connected to a microtubule-based spindle. Current models propose that displacement of the spindle poles and/or the activity of kinetochore microtubules generate mechanical forces that segregate sister chromatids. Using laser destruction of the centrosomes during Caenorhabditis elegans mitosis, we show that neither of these mechanisms is necessary to achieve proper chromatid segregation. Our results strongly suggest that an outward force generated by the spindle midzone, independently of centrosomes, is sufficient to segregate chromosomes in mitotic cells. Using mutant and RNAi analysis, we show that the microtubule-bundling protein SPD-1/MAP-65 and BMK-1/kinesin-5 act as a brake opposing the force generated by the spindle midzone. Conversely, we identify a novel role for two microtubule-growth and nucleation agents, Ran and CLASP, in the establishment of the centrosome-independent force during anaphase. Their involvement raises the interesting possibility that microtubule polymerization of midzone microtubules is continuously required to sustain chromosome segregation during mitosis.


Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Segregação de Cromossomos , Cinesinas/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Mitose , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Fuso Acromático/metabolismo , Animais , Animais Geneticamente Modificados , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiologia , Cromátides , Microtúbulos/metabolismo , Mitose/genética , Interferência de RNA , Proteína ran de Ligação ao GTP
2.
J Cell Biol ; 201(5): 653-62, 2013 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-23690175

RESUMO

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.


Assuntos
Caenorhabditis elegans/embriologia , Polaridade Celular , Embrião não Mamífero/citologia , Fuso Acromático/fisiologia , Animais , Evolução Biológica , Caenorhabditis/embriologia , Caenorhabditis/metabolismo , Caenorhabditis/ultraestrutura , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/ultraestrutura , Proteínas de Caenorhabditis elegans/análise , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/fisiologia , Proteínas de Ciclo Celular/análise , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/fisiologia
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