Fig. 2.

Neural tube defects in MEKK4-/- mice. (A) Horizontal semithin sections of E9.5 HBs showed an open neural tube in MEKK4-/- embryos (Right), whereas the neural tube of wild-type littermates was closed (Left). (B) Sagittal and coronal views of E10.5 embryos showed failed fusion of the neural tube and structural defects spanning the HB (arrows in sagittal view) to the FB (arrows in coronal view). (C) Horizontal semithin sections at E10.5 showed failed neural tube closure at the LT and an open HB in MEKK4-/- mice (Right). The FB of MEKK4-/- embryos also had ventricular stenosis, yielding a more dense appearance of the FB (see sagittal view in B). (Bars, 100 μmin A; 1,000 μm in B.)