Chromatin shapes the mitotic spindle.
In animal and plant cells, mitotic chromatin locally generates microtubules that self-organize into a mitotic spindle, and its dimensions and bipolar symmetry are essential for accurate chromosome segregation. By immobilizing microscopic chromatin-coated beads on slide surfaces using a microprinting technique, we have examined the effect of chromatin on the dimensions and symmetry of spindles in Xenopus laevis cytoplasmic extracts. While circular spots with diameters around 14-18 microm trigger bipolar spindle formation, larger spots generate an incorrect number of poles. We also examined lines of chromatin with various dimensions. Their length determined the number of poles that formed, with a 6 x 18 microm rectangular patch generating normal spindle morphology. Around longer lines, multiple poles formed and the structures were disorganized. While lines thinner than 10 mum generated symmetric structures, thicker lines induced the formation of asymmetric structures where all microtubules are on the same side of the line. Our results show that chromatin defines spindle shape and orientation. For a video summary of this article, see the PaperFlick file available with the online Supplemental Data.
Dinarina
Ana
A
Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg D-69117, Germany.
Pugieux
Céline
C
Corral
Maria Mora
MM
Loose
Martin
M
Spatz
Joachim
J
Karsenti
Eric
E
Nédélec
François
F
D000818:Animals; D002457:Cell Extracts; D002843:Chromatin / Q000737:chemistry*; D004398:Dyneins / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism; D008941:Spindle Apparatus / Q000737:chemistry*; D029867:Xenopus Proteins / Q000378:metabolism; D014982:Xenopus laevis
D002457:Cell Extracts; D002843:Chromatin; C088335:KIF11 protein, Xenopus; D029867:Xenopus Proteins; D004398:Dyneins; D016547:Kinesins