Different actomyosin regulators control apical nuclear movements in hindbrain and retinal cells. (A–C) Representative time-series of hindbrain and retinal cells treated with different actomyosin inhibitors (Video 5). (A’–C’) Representative trajectories of treated cells. Samples were incubated in DMSO (A and A’), 125 µM Rockout (ROCK inhibitor; B and B’), or 15 µM SMIFH2 (C and C’). (D and E) Percentage of G2 nuclei in samples treated with Rockout (D) or SMIFH2 (E) unable to reach the apical side in hindbrain (HB) and retina (R). Error bars: SD. P = 0.0001 for Rockout-treated and P = 0.0050 for SMIFH2-treated samples, Mann-Whitney test. (F and G) Representative time series of hindbrain and retinal cells expressing heat shock–induced DN-Rok2-EGFP (cyan; F) and GFP-PCNA (gray) or Fmnl3ΔC-EGFP (cyan; G) and mKate2-PCNA (gray; Video 8). (H) Representative time series of hindbrain and retinal cells expressing Fmnl3-EGFP (maximum intensity projection; lookup table indicates minimal and maximal Fmnl3-EGFP signal values) and mKate2-PCNA (gray; Video 8). (H’) Orthogonal (x-z) cross section of the retinal cell’s basal process. Fmnl3-EGFP is seen enriched basally of the retinal nucleus. Scale bars: 5 µm. (I) Proof-of-principle theoretical model of a pushing mechanism that could drive apical nuclear migration in the retina (for details, see Discussion and Online supplemental text).