Fig. 10. Head morphology from -/- mice at E12.5. (A) Heads from two E12.5 littermates after fixation, one hemizygous (he) and one knockout (ko) as indicated. Note the near normal appearance of the eyes and the facial structures, but the clearly abnormal doming of the skull and the smaller head of the -/- littermate. (B) Coronal sections from wild-type (top row) and knockout (bottom row) littermate mice at E12.5, stained with Hematoxylin and Eosin. In the most rostral (r) sections (left panels), the brains appear somewhat similar, showing both lateral ventricles (LV) and apparently normal midline structures, although the brains were somewhat smaller in the knockout mice. In more caudal (c) sections (middle panels), however, there was a striking loss of midline structures and the formation of a single central ventricle. In still more caudal sections (right panels), taken at the level of the retinas, there were continued striking abnormalities and loss of essentially all dorsal midline structures in the knockout mice. ihf, interhemispheric fissure; cing. cortex, cingulate cortex; gang. em., ganglionic eminence; pc, posterior commissure; epithal., epithalamus; hip., hippocampus; hypothal., hypothalamus. See the text for further details.