A centriole- and RanGTP-independent spindle assembly pathway in meiosis I of vertebrate oocytes.
Spindle formation is essential for stable inheritance of genetic material. Experiments in various systems indicate that Ran GTPase is crucial for meiotic and mitotic spindle assembly. Such an important role for Ran in chromatin-induced spindle assembly was initially demonstrated in Xenopus laevis egg extracts. However, the requirement of RanGTP in living meiotic cells has not been shown. In this study, we used a fluorescence resonance energy transfer probe to measure RanGTP-regulated release of importin beta. A RanGTP-regulated gradient was established during meiosis I and was centered on chromosomes throughout mouse meiotic maturation. Manipulating levels of RanGTP in mice and X. laevis oocytes did not inhibit assembly of functional meiosis I spindles. However, meiosis II spindle assembly did not tolerate changes in the level of RanGTP in both species. These findings suggest that a mechanism common to vertebrates promotes meiosis I spindle formation in the absence of chromatin-induced microtubule production and centriole-based microtubule organizing centers.
Dumont
Julien
J
UMR7622, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, 75005 Paris, France.
Petri
Sebastian
S
Pellegrin
Franz
F
Terret
Marie-Emilie
ME
Bohnsack
Markus T
MT
Rassinier
Pascale
P
Georget
Virginie
V
Kalab
Petr
P
Gruss
Oliver J
OJ
Verlhac
Marie-Hélène
MH
D000818:Animals; D002502:Centrioles / Q000378:metabolism*; D033481:Chromosomes, Mammalian / Q000378:metabolism; D005260:Female; D031541:Fluorescence Resonance Energy Transfer; D006160:Guanosine Triphosphate / Q000378:metabolism; D008540:Meiosis / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016376:Oligonucleotides, Antisense; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D014714:Vertebrates; D014982:Xenopus laevis; D028961:beta Karyopherins / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D016376:Oligonucleotides, Antisense; C102460:Ran protein, mouse; D028961:beta Karyopherins; D006160:Guanosine Triphosphate; D020559:Monomeric GTP-Binding Proteins; D020931:ran GTP-Binding Protein