Fig 6. Actin redistribution enables cell elongation in concert with cell proliferation.
(A) Phalloidin signal before (30 hpf) and after (42 hpf) actin redistribution in the heterozygous (hdac1+/−) controls and hdac1−/− samples. Basolateral actin accumulation does not redistribute in hdac1−/− samples (bottom panels). Lookup table indicates minimal and maximal phalloidin signal values. (B), (C) Normalized average intensity distributions of DRAQ5 (B) and phalloidin (C) signal in control (blue) and hdac1−/− (green) samples at 42 hpf. Values in each sample are normalized to minimum and maximum values. Data are shown as mean ± SEM; 3–9 samples/stage. (D) Basal-to-lateral phalloidin signal intensity ratios in hdac1−/− samples; 5 samples/stage. Mean ± SD. Mann-Whitney test, p-value 0.3095. (E) Tissue height measurements from live embryos (light sheet time lapses) for wild-type (blue) and hdac1−/− (green) samples related to S5 Movie). N = 2/condition. (F) Cell shape analyzed as aspect ratios from mean cell cross-sectional area and height in wild-type (blue) and hdac1−/− (green) samples; 3–10 samples/stage. Wild-type data same as in Fig 2E. (F’) Tissue shape analyzed as aspect ratios from mean tissue area and height in wild-type (blue) and hdac1−/− (green) samples; 3–10 samples/stage. Wild-type data same as in Fig 2E. (F”) Schematic representation of the unchanged cell aspect ratio during hdac1−/− retinal PSE growth and perturbed tissue shape. Related to S5 Movie. (G) Prediction of simplified theory for the tissue aspect ratio in the model described in Fig 5C and 5D (blue line) and in a model in which the actomyosin does not redistribute from apicobasal junctions to the lateral cortex (green dotted line, see S1 Text for details, compare with Fig 6F’). (H) Rockout treatment (175 μM) abolishes the basolateral actin accumulation but is insufficient to induce cell elongation. Scale bar: 50 μm. Actin is labeled by SiR-actin (green), and nuclei by Tg(H2AF/Z::GFP) (magenta). (I) Proliferation is necessary for cell elongation. After HU/A treatment (30 mM HU + 150 μM A), cell proliferation is blocked, but cell height does not increase (see also S6 Fig). Actin is labeled by Tg(actb1::GFP-UtrCH) (green), and nuclei by Tg(b-actin::H2B-RFP) (magenta). (Underlying data can be found at DOI: 10.5281/zenodo.1316912; for panels B and C at /Matejcic-et-al_2018/Data/ F4CDE_6BC.csv, panel D at F5B_6D_S6.csv, panel E at F6E.csv, panels F and F’ at F6F.csv. The theoretical analysis for panel G can be found at /Matejcic-et-al_2018/Theory/Data analysis_essentials.nb.). A, aphidicolin; DRAQ5, deep red anthraquinone 5; hdac1, histone-deacetylase 1; hpf, hours post fertilization; HU, hydroxyurea; n.s., not significant; PSE, pseudostratified epithelium.