Fig. 3. Floor plate induction and ventral neural tube patterning is affected in Ftm^-/- embryos. (A-H) In situ hybridizations on sections at stage E11.5. In the wild type mouse, Shh is expressed in the notochord (green arrowhead) and in the floor plate (blue arrowhead) (A), and Foxa2 expression is restricted to the floor plate (B). In Ftm^-/- embryos, Shh expression in the floor plate is absent (C), and Foxa2 expression is lost (D). In wild-type embryos, Ptc1 is expressed within the neural tube and the mesenchyme sourrounding the notochord (E), and Irx3 is expressed within the whole neural tube except the most ventral region (F). In Ftm^-/- embryos, expression of Ptc1 is strongly reduced (G). Irx3-positive cells are expanded into the most ventral part of the neural tube, including the midline (expression borders are marked with red bars) (H). (I-P) Immunohistochemistry at stage E11.5. In wild-type embryos, Shh protein is detectable in the floor plate (white arrowhead) and notochord (green arrowhead) (I), and Nkx2.2-expressing cells are found adjacent to the floor plate (J; white arrowhead). Ftm^-/- embryos show a loss of Shh protein in the floor plate (K), and Nkx2.2-expressing cells are greatly reduced (L). In the wild type, MNR2-positive cells are located in two lateral domains (M), and Pax6-expressing cells are restricted to the dorsal neural tube. In Ftm^-/- embryos, only a few MNR2-postive cells are found in a spotted fashion (O), and Pax6-expressing cells are expanded into the most ventral part of the neural tube (expression borders are marked with white bars) (P).