Fig. 1. Induction of En2 by FGF signaling. Dissected brains from HH19-21 chick embryos whole-mount immunostained for En2. Electroporation (EP) was done at HH8 with GFP only (A), constitutively active Fgfr3 (B), constitutively active Fgfr1 (C) and Fgf8b (E) in the fore-midbrain region. Areas of the transgene expression were monitored by expression of GFP co-electroporated (D,F). Ectopic En2 expression is detected in the posterior diencephalon (arrows in B,C), and bordered by the zona limitans intrathalamica (ZLI; dashed lines in C), although the transgenes are expressed more anteriorly (arrowheads in D,F). Bars, 0.5 mm. di, diencephalon; is, isthmus; me, mesencephalon; os, optic stalk; rh, rhombencephalon; te, telencephalon.