Fig. 2.

Magnetic resonance microscopy of normal and abnormal brain development. Scale bars = 1 mm, axes: d – dorsal; v – ventral; r – right; l – left; a – anterior; p – posterior. Individual embryo numbers are indicated at the top right in each panel. (a) Sagittal midline section through a wild-type normal embryo showing the spinal cord (sc), medulla oblongata (mo), cerebellum (c), pons (po), midbrain (mb), midbrain roof (mbr), hypothalamus (h), developing pituitary gland (p), thalamus (th), and forebrain (fb). Also seen are the mesencephalic vesicle (mv), the aqueduct of Sylvius (aq), the choroid plexus (cp) in the fourth ventricle, palate (pa), and the tongue (t). (b–d) Transverse sections through the planes indicated by arrows in panel a also show the telencephalic vesicle (tv), the inner ear (ie), the eyes (e), the trigeminal ganglia (v) and the nasal cavity (nc). (e–l) Sagittal (e,i) and transverse (f–h, j–l) sections through two Cited2^−/− embryos showing exencephaly, which begins at the junction of the spinal cord and medulla. The transverse section planes are indicated by arrows in panels e and i. In both embryos, the midbrain roof and cerebellum are absent. The abnormal structure (x) is continuous with the mid-brain region, and represents the everted neuroectoderm.