Fig. 6. Analysis of cell death in the Fgf8 mutants at E9.0. TUNEL analysis on horizontal sections through the E9.0 forebrain labels apoptotic cells in wild-type (A-E), Fgf8^Null/Neo (A'-E') and Fgf8^TelKO embryos (A''-E''). A-A'' are the most ventral; E-E'' are the most dorsal. Note, sections B,B',B'' are the same as in Fig. 5. Black arrowheads indicate the rostral midline; white arrowheads indicate the apoptotic cells in the telencephalic primordium (A',B',B'',C'') and at the junction of the dorsal optic stalk with the telencephalon (D',D'',E',E''). HT, hypothalamus; Os, optic stalk; Tel, telencephalon.