Fig. 3. Canonical Wnt signalling inhibits neuronal differentiation. (A,A') Electroporation of control IRES-GFP/PCINeo vector (A, Fast Red, GFP transcripts) has no effect on NeuroM (A'). (B,B') Electroporation of Wnt8c-IRES-GFP/PCINeo (B), reduces the amount of NeuroM-positive cells (B'). (C) Quantification of results shown in (A-B'): the percentage of NeuroM-positive cells on the electroporated side is significantly lower in presence of Wnt8c (four sectioned embryos), compared with the control (five sectioned embryos) (t-test, P=0.01). (D) Origin of neural tube (NT), preneural tube (pNT) and underlying presomitic mesoderm (PSM) explants used in (E-J'). (E-F') pNT explants either combined with control cells (E) or Wnt8c cells (E'), or cultured in control media (F) or media supplemented with LiCl (F'). Fewer NeuroM+ cells arise in pNT exposed for 24 hours to Wnt8c or to LiCl. (G-H') NT in control media (G-J), with FGF4 (G',I') or with LiCl (H',J'). Fewer Ngn1+ cells are present in NT exposed to FGF4 (I') or to LiCl (J'). Scale bars: 25 µm in A for A,A'; 20 µm in B for B,B'; 50 µm in E for E-F' and in G for G-H'.