Fluctuation Analysis of Centrosomes Reveals a Cortical Function of Kinesin-1.
The actin and microtubule networks form the dynamic cytoskeleton. Network dynamics is driven by molecular motors applying force onto the networks and the interactions between the networks. Here we assay the dynamics of centrosomes in the scale of seconds as a proxy for the movement of microtubule asters. With this assay we want to detect the role of specific motors and of network interaction. During interphase of syncytial embryos of Drosophila, cortical actin and the microtubule network depend on each other. Centrosomes induce cortical actin to form caps, whereas F-actin anchors microtubules to the cortex. In addition, lateral interactions between microtubule asters are assumed to be important for regular spatial organization of the syncytial embryo. The functional interaction between the microtubule asters and cortical actin has been largely analyzed in a static manner, so far. We recorded the movement of centrosomes at 1 Hz and analyzed their fluctuations for two processes—pair separation and individual movement. We found that F-actin is required for directional movements during initial centrosome pair separation, because separation proceeds in a diffusive manner in latrunculin-injected embryos. For assaying individual movement, we established a fluctuation parameter as the deviation from temporally and spatially slowly varying drift movements. By analysis of mutant and drug-injected embryos, we found that the fluctuations were suppressed by both cortical actin and microtubules. Surprisingly, the microtubule motor Kinesin-1 also suppressed fluctuations to a similar degree as F-actin. Kinesin-1 may mediate linkage of the microtubule (+)-ends to the actin cortex. Consistent with this model is our finding that Kinesin-1-GFP accumulates at the cortical actin caps.
Institute for Developmental Biochemistry, Medical School, Georg-August-University Göttingen, Göttingen, Germany.
Franziska
F
Winkler
Institute for Developmental Biochemistry, Medical School, Georg-August-University Göttingen, Göttingen, Germany.
Maheshwar
M
Gummalla
Institute for Theoretical Physics, Georg-August-University Göttingen, Göttingen, Germany.
Lutz
L
Künneke
Institute for Developmental Biochemistry, Medical School, Georg-August-University Göttingen, Göttingen, Germany.
Zhiyi
Z
Lv
Institute for Theoretical Physics, Georg-August-University Göttingen, Göttingen, Germany.
Annette
A
Zippelius
Institute for Mathematical Stochastics, Georg-August-University Göttingen, Göttingen, Germany; Felix Bernstein Institute for Statistics in the Biosciences, Georg-August-University Göttingen, Göttingen, Germany.
Timo
T
Aspelmeier
Institute for Developmental Biochemistry, Medical School, Georg-August-University Göttingen, Göttingen, Germany. Electronic address: jgrossh@gwdg.de.
Jörg
J
Grosshans
D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D018385:Centrosome / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster; D016547:Kinesins / Q000378:metabolism*; D008954:Models, Biological; D009068:Movement; D024462:Myosin Type II
D029721:Drosophila Proteins; D024462:Myosin Type II; D016547:Kinesins