Fig. 5. Holoprosencephaly in Tsg^-/-;Bmp4^+/- embryos at E15.5. (A-A') E15.5 wild-type and Tsg^-/-;Bmp4^+/- embryos. The plane of sections shown below are designated b,b',c and c'. (B,B',C,C') Histological sections were stained with Hematoxylin and Eosin. The lateral ganglionic eminence (lge) is missing and the floor of the diencephalon (fd) is greatly thickened in the mutant. Note the fusion of the lateral ventricles, owing to the lack of a medial wall (mw) and the lack of nasal septum (ns). In addition, note the empty orbits (ob), lack of lens (ls) and retina (re) of the eyes. di, diencephalon; hy, hypothalamus; ll, lower lid; lv, lateral ventricle; ol, olfactory epithelium; to, tongue; ul, upper lid; vi, follicles of vibrissae; 3V, third ventricle.