Fig. 4. Neurogenesis is perturbed in the Fgfr1^-/- ;Fgfr3^-/- and Fgfr1^-/- ; Fgfr2^-/- mutants. (A-L) RNA in situ hybridization analysis of E12.5 coronal brain sections using radioactive probes. Shh and Lhx7 are normally expressed in differentiating cells of the medial ganglionic eminence (A,D); however, this expression is lost in the mutants (B,C,E,F). Ebf1, on the other hand, which is normally expressed in differentiating cells of the lateral ganglionic eminence (G), remains expressed in the Fgfr1^-/-;Fgfr3^-/- mutant (H), but not the Fgfr1^-/-;Fgfr2^-/- mutant (I). Mash1, which is normally expressed in ventral precursors (J), remains expressed in the Fgfr1^-/-;Fgfr3^-/- (K) but not the Fgfr1^-/-;Fgfr2^-/- (L) mutant. (M-S) RNA in situ hybridization of E16.5 coronal brain sections. Gad67 expression is lost in Foxg1-expressing areas (arrows) of the Fgfr1^-/-;Fgfr2^-/- mutant at the expense of Tag1 expression (O,R,S), whereas in the Fgfr1^-/-;Fgfr3^-/- mutant, the boundaries of Gad67 and Tag1 expression are normal (M,N,P,Q). Scale bars: 0.5 mm in A-L; 1 mm in M-S.