A positive-feedback-based mechanism for constriction rate acceleration during cytokinesis in Caenorhabditis elegans
- University of California, San Diego, United States
Figures
Figure 1 with 3 supplements
A quantitative map of cortical surface dynamics during the first cytokinesis in the C. elegans embryo reveals that the cortical surface at the cell poles expands as the ring constricts.
(A) (top) Schematic of the experimental procedure. (middle, left) Superposition of images of the cortex acquired 4 s apart. Arrows indicate cortical flow (magnified 2.5X). (middle, right) The …
Figure 1—figure supplement 1
Actin and myosin move together with the cortical surface during cytokinesis.
(A) Schematic of the single-copy nmy-2::gfp transgene inserted into a specific locus on chromosome II. Cb unc-119, the unc-119 coding region from the related nematode C. briggsae, was used as a …
Figure 1—figure supplement 2
An automated method for monitoring contractile ring closure.
(top) Central plane images of the embryo in Figure 1A. Panels on the lower left and lower right are reproduced from Figure 1A for comparison. An automated algorithm was used to identify the edges of …
Figure 1—figure supplement 3
Different profiles of cortical surface velocity along the A-P axis are predicted for different spatial patterns of surface expansion.
(top) For surface expansion behind the ring, no cortical movement is predicted on the embryo surface. (middle) For uniform surface expansion, a gradient of velocities will be observed, where the …
Figure 2 with 1 supplement
Cortical tension does not limit the rate of ring closure.
(A) The success of cortical cuts was assessed by comparing surface images of cortical myosin before (cyan) and after (red) the cut to monitor the movement of myosin foci away from the cut site. …
Figure 2—figure supplement 1
Arp2/3 depletion does not alter ring constriction kinetics.
(A) Images of cortical ARX-2::GFP (top) and GFP::ARX-7 (middle) in control and arx-2(RNAi) embryos confirm loss of cortical Arp2/3 complex (images are representative of 10 imaged embryos for each …
Figure 3 with 4 supplements
Ring myosin compresses cortical surface along the axis perpendicular to the ring, pulling in new cortical surface at a rate proportional to the amount of ring myosin.
(A) The equatorial cortex is compressed during contractile ring assembly. Following the onset of spindle-based RhoA signaling, the initial recruitment of contractile ring proteins leads to uniform …
Figure 3—figure supplement 1
Arp2/3 inhibition abolishes the asymmetry in the amount of cortex entering the division plane from the anterior and posterior sides.
Graphs plot the rate of cortical flux across the anterior (light grey) and posterior (dark grey) boundaries (see schematic in Figure 3B) versus the mean for the two sides (purple) for control and arx…
Figure 3—figure supplement 2
GFP::anillin fluorescence in the ring increases exponentially during constriction.
(A) (left) Schematic of the single-copy gfp::ani-1 trangene. The transgene was re-encoded while maintaining amino acid sequence in the indicated region to render it resistant to RNAi targeting of …
Figure 3—figure supplement 3
Correcting for signal attenuation with sample depth.
Fluorescence attenuation with embryo depth was estimated from fluorescence intensity measurements made at the cell-cell boundary of two-cell embryos expressing a GFP-tagged plasma membrane marker. …
Figure 3—figure supplement 4
Ring component dynamics at the four-cell stage are consistent with exponential accumulation.
(A) (left) Schematic illustrating the relative geometries of cytokinesis in one- and four-cell stage C. elegans embryos. (right) The range of ring sizes between furrow formation and contact with the …
Figure 4
Constriction-coupled disassembly with compression feedback model.
(A) The natural coordinate system for contractile ring dynamics has two axes, an axis parallel to ring constriction (around-the-ring axis) and an axis perpendicular to the ring (perpendicular-to-the-…
Figure 5 with 1 supplement
Myosin accumulation and the rates of ring constriction and cortical compression can be approximated with a retention model but are fit better by the Constriction-Coupled Disassembly with Compression Feedback model.
(A) Two models could explain the acceleration in the per-unit-length constriction rate during constriction. In the Constriction-Coupled Disassembly with Compression Feedback model, the increase in …
Figure 5—figure supplement 1
Total myosin::GFP and GFP::anillin in the ring.
Graphs plotting mean total ring fluorescence (average over all angles; green) for myosin::GFP (n = 36 embryos) and GFP::anillin (n = 26 embryos). Error bars are the SEM. The predictions for the …
Figure 6
Fluorescence recovery after photobleaching of the division plane at the one-cell stage rules out Retention and is consistent with Constriction-Coupled Disassembly with Compression Feedback.
(A) (top) Schematic of the photobleaching experiment. (bottom) Images of the division plane reconstructed from 30 × 1 μm z-stacks of an embryo expressing myosin::GFP whose division plane was …
Figure 7
Fluorescence recovery after photobleaching of the division plane at the four-cell stage is consistent with Constriction-Coupled Disassembly with Compression Feedback.
(A) (top) Schematics of an experiment that we performed previously in which a spot was bleached in contractile rings at the four-cell stage (Carvalho et al., 2009). In kymographs of a fixed length …
Figure 8
The Constriction-Coupled Disassembly with Compression Feedback model for contractile ring dynamics during cytokinesis.
Polar relaxation allows ring myosin to compress cortical surface along the axis perpendicular to the ring. Compression pulls naive cortex not previously exposed to RhoA-based signaling into the …
Author response image 1
Cortical flows during cytokinesis are not altered in NOP-1-depleted embryos.
(A) nop-1(RNAi) embryos were monitored prior to the first mitotic division to confirm that pseudocleavage failed indicating successful NOP-1 depletion. (B) Fluorescence confocal images showing that …
Author Response Image 2
Amounts of myosin::GFP and GFP:anillin per unit ring length measured at the 4-cell stage.
© 2009 Elsevier. Author response image 2 reproduced with permission from Carvalho et al., 2009.
Author response image 3
Technical limitations prevent imaging of cortical flow at the cell poles.
https://doi.org/10.7554/eLife.36073.026
Author response image 4
Comparison of the Retention model fit without (A) and with (B) inclusion of a baseline term.
https://doi.org/10.7554/eLife.36073.027
Author response image 5
(A) New 4-cell stage data. Images of the division plane in a representative dividing cell at the 4-cell stage reconstructed from 16x1μm z-stacks of an embryo expressing myosin::GFP from an in situ …
Author response image 6
(A) (left) Spinning disk confocal optics were used to collect a 4x1μm z-series containing the embryo cortex and a maximum intensity projection is shown 220s after nuclear envelope breakdown (NEBD). …
Videos
Video 1
Cortical flow imaged in a control embryo expressing myosin::GFP.
Playback is 6x realtime. The video is constructed from maximum intensity projection of 3 × 0.75 µm plane z-stacks acquired at 2 s intervals. The red line marks the position of the division plane. …
Video 2
Average cortical flow map calculated from time lapse imaging of the cell surface in 93 control embryos expressing myosin::GFP. (top, left)
Schematic illustrates location of the cylindrical surface covered by the map. (top, right) Dynamic schematic illustrates ring size and position for each value of t/tCK. (bottom, left) The movement …
Video 3
Average cortical flow map calculated from time lapse imaging of the cell surface in 68 arx-2(RNAi) embryos expressing Myosin::GFP.
(top, left) Schematic illustrates the location of the cylindrical surface covered by the map. (top, right) Dynamic schematic illustrates ring size and position for each value of t/tck. (bottom, left)…
Tables
Key resources table
| Strain name | Genotype | Reference |
|---|---|---|
| OD821 | ltSi200[pOD1997; Pnmy-2::nmy-2::gfp; cb-unc-119(+)] II; unc-119(ed3) III | This study |
| OD857 | ltSi200[pOD1997; Pnmy-2::nmy-2::gfp; cb-unc-119(+)] II; unc-119(ed3); ruIs32[pAZ132; pie-1/GFP::histone H2B] III | This study |
| OD858 | ltSi803[pOD1998; Parx-7::GFP::arx-7; cb-unc-119(+)] II; unc-119(ed3) III; | This study |
| LP162 | nmy-2(cp13[nmy-2::gfp + LoxP]) I | Dickinson et al., 2013 |
| OD95 | unc-119(ed3) III; ltIs37 [pAA64; Ppie-1::mCherry::his-58; unc-119(+)] IV; ltIs38 [pAA1; Ppie-1::GFP::PH(PLC1delta1); unc-119 (+)] | Essex et al., 2009 |
| OD3011 | ltSi1123[pSG017; Pani-1::GFP::ani-1 RE-encoded-exon5::ani-1 3'-UTR; cb unc-119(+)]II;unc-119(ed3)III | This study |
| GOU2047 | cas607[arx‐2::gfp knock‐in] V | Zhu et al., 2016 |
Additional files
-
Transparent reporting form
- https://doi.org/10.7554/eLife.36073.022
