Fig. 7

Actin Comet Formation in Ooplasm-Yolk Granules Segregation

(A) YG velocity vector field taken from 2D flow simulations with a zero-stress blastodisc-YGs interface (BYI). The box corresponds to zoomed-in view of YGs velocity vector field at BYI. Color code ranges from high + (red) to high − (blue) velocities.

(B) Images of oocytes expressing Rac1-NGreen to mark ooplasm and YGs. Dashed white lines indicate BYI.

(C) Averaged central BYI displacement (cyan, left axis) and ooplasm flow velocity (magenta, right axis) from 30–70 mpf. N = 3 experiment, n = 5 oocytes. Ooplasm flow velocity data are taken from Figure 1G. The green and golden boxes indicate the straightening and protruding phases when the central BYI changes its shape.

(D) Images of oocytes expressing Utr-GFP to mark F-actin (red) and exposed to NileRed to mark YGs (green). White and blue boxes indicate the ROIs used for measuring actin intensity in the ooplasm or on the YGs surface in D′, respectively. Yellow ROI indicates the area used for zoomed-in images in (D″).

(D′) Ratio of actin intensities on YGs surface (blue box in D) relative to ooplasm (white box in D) during bulk actin polymerization wave. N = 3, n = 3.

(D″) Zoomed-in view of YGs and bulk actin at the ROI indicated in (D). Arrowheads demarcate the formation of actin comets on the ooplasm facing side of YGs.

(E) Averaged displacement of YGs at the BYI during bulk actin polymerization wave. Period of wave propagation is marked in green. N = 2, n = 2.

(F) Kymograph of YGs (green) and F-actin (red) displacement along the AV axis as a function of time. Kymograph was taken at the position within the oocyte marked by white dashed line in (D, left panel). Arrowheads demarcate actin on YGs surface.

(G) Images of F-actin in oocytes. Yellow arrowheads indicate comet formation events around several YGs at the BYI.

(H) Images of F-actin (red) and YGs (green and segmented in cyan) in oocytes.

(I) Measured (left, averaged from PIV analysis of YGs over the first 5 min of the first protruding phase, N = 1, n = 3) and simulated (right, in the absence of stress at BYI) YGs velocity vector fields during the protruding phase. Color code ranges from high + (red) to high − (blue) velocities.

(I′) Measured (left, averaged from PIV analysis of YGs over the first 5 min of the second straightening phase, N = 1, n = 3) and simulated (right, in the presence of stress at BYI) YGs velocity vector fields during the straightening phase. The box corresponds to zoomed-in view of YGs velocities at BYI.

(J) Images of F-actin in WT (top row) and dchs mutant (bottom row) oocytes during the first two actin polymerization waves. Arrowheads indicate actin comet formation on YGs surface at BYI.

(K) Ratio of actin intensities on YGs surface relative to ooplasm during bulk actin polymerization wave for WT (cyan, N = 3, n = 6, same data as in D′) and dchs mutant oocytes (magenta, N = 3, n = 8).

(L) Amplitudes of actin oscillations during the first three actin polymerization waves for WT (cyan, N = 3, n = 5) and dchs mutant oocytes (magenta, N = 3, n = 5).

Error bars, SEM. Mann-Whitney tests, ns, not significant, ^∗∗∗∗p < 0.001.