Profound malformation of the mutant hChP. (A,A′) Nissl staining of P18 mice frontal sections reveals the near-complete absence of the hindbrain ChP (hChP) in the fourth ventricle of the Zfp423 mutant (red arrowhead in A′) compared with the wild type (white arrowhead in A). A small lateral segment of the hChP is visible in wild type and mutants (insets). (B,B′) Nissl staining of E14.5 parasagittal sections shows a severe hChP hypoplasia in the mutant compared with wild type, with a flattened surface (red arrowhead in B′) compared with the wild type (white arrowhead in B). (C,C′) Conversely, the mutant tChP shows a more-normal morphology compared with the wild type (white arrowhead in C,C′). Med, medial cerebellar nucleus; Lat, lateral nucleus; Cx, cortex; hChP, hindbrain ChP; tChP, telencephalic ChP; Hb, ventral hindbrain; Hi, hippocampus; IV, fourth ventricle; Mes, mesencephalon; Url, rhombic lip; Vz, ventricular zone. Scale bars: 200 μm in A; 100 μm in B; 400 μm in C.