Self-organization of microtubules into bipolar spindles around artificial chromosomes in Xenopus egg extracts.
Functional nuclei and mitotic spindles are shown to assemble around DNA-coated beads incubated in Xenopus egg extracts. Bipolar spindles assemble in the absence of centrosomes and kinetochores, indicating that bipolarity is an intrinsic property of microtubules assembling around chromatin in a mitotic cytoplasm. Microtubules nucleated at dispersed sites with random polarity rearrange into two arrays of uniform polarity. Spindle-pole formation requires cytoplasmic dynein-dependent translocation of microtubules across one another. It is proposed that spindles form in the absence of centrosomes by motor-dependent sorting of microtubules according to their polarity.
Heald
R
R
Mitotic Spindle Group in the Cell Biology Program, EMBL, Heidelberg, Germany.
Tournebize
R
R
Blank
T
T
Sandaltzopoulos
R
R
Becker
P
P
Hyman
A
A
Karsenti
E
E
D000818:Animals; D002457:Cell Extracts; D002843:Chromatin / Q000502:physiology / Q000648:ultrastructure; D002875:Chromosomes / Q000502:physiology*; D004330:Drosophila / Q000235:genetics; D004398:Dyneins / Q000502:physiology; D008297:Male; D008863:Microspheres; D008870:Microtubules / Q000502:physiology*; D008938:Mitosis / Q000502:physiology; D010063:Ovum / Q000502:physiology; D010957:Plasmids; D013094:Spermatozoa / Q000502:physiology; D008941:Spindle Apparatus / Q000502:physiology*; D014981:Xenopus
D002457:Cell Extracts; D002843:Chromatin; D004398:Dyneins