Fig. 7. Abnormalities in extent, identity and fate of progenitor domains. (A-F) In situ hybridisation (A-E) and immunohistochemistry (F) on whole-mount embryos focussing on sagittal view of the ventral midbrain of En1^cre/+ and En1^cre/+; Otx2^flox/flox embryos at E12.5 and E11.2 with Fgf8 (A), Pou4f1 (B), Th (C), Isl1 (D), Pet1 (E) probes and 2H3 (F) antibody. (G-ß) Immunohistochemistry (G-R,W-ß) and in situ hybridisation (S-V) at E12.5 in the midbrain of En1^cre/+, En1^cre/+; Otx2^flox/flox and En1^cre/+; Otx2^flox/flox; Otx1^-/- embryos and in the rostral hindbrain (M-R) of En1^cre/+ embryos with Nkx6.1 (G,M,W), Nkx2.2 (H,N,X), Pou4f1 (I,O,Y), Th (J,P,Z), Isl1 (K,Q,) and 5-HT (L,R,ß) antibodies and with Otx2 (S), Fgf8 (T), Th (U) and Sert (V) probes. () Schematic representation summarising the expression pattern of Shh, Nkx6.1 and Nkx2.2 and neuronal cell types detected in control and mutant embryos. The broken lines in A indicate the approximate position of frontal (G-L) and horizontal (S-V, M-R) sections; the position of frontal sections of the triple mutant (W-ß) are at a level similar to that of the conditional mutant, but in the triple mutant this position is posterior to Fgf8 expression; the arrowheads in B-E and the arrows in S,U,V indicate the corresponding position of Fgf8 expression and the arrows in T indicate the posterior border of functional Otx2 domain; the inset in H,N,X highlights the ventral expression of Nkx2.2; the bracket demarcates the neuroepithelium expressing Nkx2.2 and generating Ser neurons in the midbrain of mutant embryos (H,L,X,ß) and in the rostral hindbrain of control embryos (N,R). OM oculomotor nucleus; RN, red nucleus; Fb, forebrain; Mb, midbrain; Hb, hindbrain; TN, trochlear nucleus; OMn, oculomotor nerve; e, eye; DA, dopaminergic cells; Ser, serotonergic cells.