Figure 3: Short-term exposure of spinal neural progenitors in the open-book configuration with Sema3B promotes the planar orientation of their division at E10.5.

(a) Schema of the open-book surgery, Sema3B-Fc exposure and analysis of cell division orientation of spinal neuroepithelial cells in the apicobasal axis on transverse sections at the brachial and thoracic levels. (b) Cumulative fraction curves showing the distribution of apical progenitor division orientation in closed and open neural tubes exposed or not with recombinant Sema3B-Fc for 3 h at E10.5. (n, number of cells examined from at least three independent experiments and five embryos for each conditions, P value is from the Kolmogorov-Smirnov (KS) test). (c) The same data sets are reported in pie charts with four classes displaying planar (80–90°) and oblique (60–80°, 30–60° and 0–30°) divisions of spinal progenitors (P value is from Fisher’s exact test). (d) Confocal images of representative anaphase cells, with Hoechst, PH3 and γ-tubulin stainings. Division and apical planes are indicated in dotted lines (scale bar, 5 μm). (e) Staining of ZO1, F-actin, atypical PKC and Hoechst on cryosections of control embryos fixed without incubation or open-book embryos after 3-h culture. The apical architecture of the neuroepithelium in the open-book condition was preserved (scale bar, 10 μm).