Fig. 9. Loss of all CPe, including posterior tCPe, after early Gdf7-mediated ablation. Ttr in situ hybridization and Hematoxylin and Eosin stains on E12.5 and E13.5 coronal cryosections (A-D,G,H) or paraffin sections (E,F), and Ttr qRT-PCR analysis (I) on E12.5 ACTBCre;Gdf7DTA embryos and controls. (A,B) Hindbrain. The mutant hindbrain is open and lacks Ttr expression (arrows in A). (C-I) Forebrain. In the closed mutant forebrain, no Ttr expression (C) or tissue resembling CP (F,H) is detectable at E12.5 (E) or E13.5 (G). (I) Ttr qRT-PCR. Ttr transcript levels in the dorsal forebrain are two to three orders of magnitude lower in the three E12.5 mutants relative to three littermate controls after normalizing to 18S rRNA (0.004±0.003) or Cyclophilin A (0.003±0.001). Arrows designate the expected sites of CPe; d, dCPe; m, mCPe; t, tCPe. Scale bars: 0.2 mm. See Materials and methods for additional qRT-PCR details.