Figure 5.

Asymmetric cortical aPKC controls central spindle symmetry breaking

(A) SOP cell expressing mRFP-Pon as a marker of the anterior pIIb cell (the cell not inheriting the core Par complex cap) were fixed and immunostained for acetylated tubulin. Bottom: acetyl-tubulin channel with a grayscale (left) or rainbow (right) lookup table (LUT).

(B and C) Arrays were assembled on 3T3 cells stably expressing GBP-TM-GBP and indicated construct 12 h before mitotic shake-off, then stained for acetyl-tubulin. We define the side without the cap as the "anterior" and the side with the GFP-cap as the "posterior," in respect to the situation in fly SOP cells, where the aPKC cap is present on the posterior side.

(D–F) Acetyl-tubulin intensity pseudo-linescan through the central spindle (mean ± SEM see STAR Methods) in indicated samples. Statistics: paired t test between the respective peak values in each cell.

(G) Normalized enrichment of microtubule density on the anterior side (no cap) of the central spindle as a function of the protein targeted to the cap. Positive values correspond to a higher microtubule density on the anterior side (no cap), while negative values indicate an increased density on the posterior side (GFP-cap). Statistics: Mann-Whitney U test compared with GFP.

(H) Summary: synthetic Par-complex caps are sufficient to promote central spindle symmetry breaking, with lower microtubule densities on the side of the Par-cap and higher microtubule densities on the side opposite to the cap.

All panels correspond to MIPs. Scale bars: 5 μm (A–C, top) and 1 μm (A–C, bottom).

See also Figure S9.