FIGURE 3.

WNT1/b-catenin-responsiveness in the mouse VM is mediated by the activating LEF/TCF family member LEF1. (A–U) Representative overviews (A–D,F–I,K–N,P–S) and close-up views of the VM (E,J,O,P’–S’) on coronal sections (dorsal top) at medial (A–Q’,S–U) and rostral (R,R’) midbrain levels from CD-1 (A–S’) and BAT-gal⁺ (T–U) embryos at E10.5 (A–E,P–Q’), E12.5 (F–J,O,R–U) and E17.5 (K–N), hybridized with riboprobes for Lef1 (A,F,K), Tcf7 (B,G,L), Tcf7l1 (C,H,M) and Tcf7l2 (D,I,N), or immunostained with antibodies against LEF1 (green, P–S’; orange, T’,T”), SOX6 (red; P,P’,R,R’), OTX2 (red; Q,Q’,S,S’), b-GAL (green; T,T”), TH (magenta, T”; green, U) and PITX3 (red; U; same section in T–T”, adjacent section in U). (A–O), dark-field images; (E,J,O), pseudocolored overlays of consecutive sections (higher magnifications of boxed areas in A and F, respectively), hybridized with probes for Lef1 (red), Wnt1 (blue), and Aldh1a1 (green; E), Pitx3 (green, J; cyan, O), or Lmx1a (green; O); overlapping expression domains appear in magenta (red/blue), cyan (blue/green), yellow (red/green), or white (red/blue/green). Broken white lines outline the neuroepithelium (E,J,K–O) and delimit BP from lFP and mFP (E,J,O) or TH⁺/PITX3⁺ domain from LEF1⁺ domain (T–U); white lines in (J,O) delimit the VZ/SVZ, IZ, and MZ. (V) Western blot analysis of LEF1 expression in VM and DM tissues of E12.5 CD-1 mouse embryos, using two different LEF1 antibodies against the N- (C12A5) or C-terminus (C18A7) of LEF1. Detection of b-actin was used as loading control. The position of the ∼55 kDa full-length (activating) LEF1 isoform and smaller protein bands are indicated to the left. Scale bars: 200 μm (B,H); 500 μm (L); 100 μm (P); and 50 μm (Q’,R’).