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. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: Nat Cell Biol. 2015 Oct 19;17(11):1471–1483. doi: 10.1038/ncb3251

Figure 7.

Figure 7

Excitability does not require spindles but is locally modulated by microtubules (a) Still frame (top) and kymograph (bottom) from time-lapse movie showing cortical Rho activity in two nucleate fragments derived from bisection of Ect2-overexpressing starfish oocyte. Waves of Rho activity appear and disappear in synchrony in each half. Pseudocolor table shown applies to a,b,b′, and e; in a and b′, outlined strips indicate kymograph region, dashes in kymographs are times of still frames. (b) Frames from time-lapse movie showing cortical Rho activity in nucleate half (top) and anucleate cytoplast (bottom) after bisection of Ect2-overexpressing starfish oocyte just before meiosis I. Waves appear and disappear on time in anucleate cytoplast in spite of the fact that it lacks spindle, chromosomes, or even centrosomes (see Supplementary Video 17) (b′) Similar bisection but after meiosis; two frames (top), during and after first cleavage, and kymographs (bottom, 1: nucleated, 2: anucleate). Cortical Rho waves appear and disappear in both halves, although first mitosis is delayed in the anucleate cytoplast. (c) Frames from time lapse movie showing microtubules (cyan) and active Rho (gold) in normal starfish oocyte during meiosis I. Rho activity is suppressed in the region occupied by spindle aster. (d) Frames from time lapse movie showing microtubules (cyan) and active Rho (gold) in starfish zygote with two spindles. Rho activity waves are excluded from regions occupied by spindle asters leading to focusing of Rho waves into cruciform Rho zone. (e) Meiotic Rho activity in normal starfish oocyte after treatment with 5 uM nocodazole to depolymerize microtubules (see Supplementary Video 18). The overall pattern of Rho activation is similar to controls – initiation at vegetal end, rapid progression to animal pole, inactivation in M-phase – except that animal pole is a Rho hotspot instead of a suppressed area; sep=sperm entry point, ms=meiotic spindle. Images are representative of 3(a, b), 12(c),17 (d) and 3(e) independent experiments, respectively.