Figure 8

Constitutive activation of Sonic hedgehog (Shh) signaling in Shh-Cre;SmoM2 mutants leads to transient expansion of progenitors in ventral midbrain. (A-A’) In situ hybridization of Smoothened indicated overexpression of Smoothened in Shh-Cre;SmoM2 mutants at embryonic day (E)10.5. (B-B’) Immunofluorescence staining of Lmx1a on sagittal sections revealed the anterior extension of Lmx1a domains from vMB in Shh-Cre;SmoM2 mutants (B’) at E10.5. Arrow indicates the midbrain/hindbrain boundary (MHB). (C) Illustration of how a series of coronal sections were generated in the ventral midbrain (vMB) at E10.5. Whole-mount staining of Wnt1 outlines the vMB region. Coronal sections were generated by cutting vMB at 60 μm intervals. (c1-d4) Foxa2/Nkx6.1 staining: (c1-c3) in control SmoM2 mice, there were three sections with vMB floor plate feature, whereas (d1-d4) there were four sections with this feature in Shh-Cre;SmoM2 mutants. Scale bars: (A) 200 μm, (B’) 100 μm, applied to B and B’; (C’) 100 μm, applied to C and C’; (d’-1) 100 μm, applied to c1 to d’4. (E) Quantification of total number of Lmx1a, Foxa2, Nkx2.2 and Nkx6.1 cells show the increase in progenitor cells at E10.5. Student’s t test, n = 3 or 4.