Fig. 2. Induction of Sprout2 by Fgf8. sprouty2 induction at 3 hours after Fgf8a misexpression (A-D, the same embryo), and 24 hours after electroporation (E-H). E and F are form the same embryo, and G and H show the same section at the mesencephalon. (I-L,M-R) sprouty2 induction at 3 hours after Fgf8b misexpression (I-L, the same embryo), and 24 hours after electroporation (M-R, M,N and Q,R are from the same embryo). O and P are higher magnifications of the areas indicated as O and P on M and N, respectively. (S) Electroporation of mouse Fgf8b and hybridization with cFgf8 and mFgf8 probes that do not cross hybridize each other. In situ hybridization for Fgf8 (A,C,E,G,I,K,M,O,Q), for sprouty2 (B,D,F,H,J,L,N,P,R). At 3 hours after electroporation with Fgf8a vector (HH 9), misexpression of Fgf8 is easily discernible (A,C), and sprouty2 is induced overlapping Fgf8 expression (B,D). At 24 hours after electroporation, Fgf8 misexpression can be discerned in a wide area (E). sprouty2 is expressed overlapping Fgf8 (E-H). At 3 hours after electroporation with Fgf8b expression vector, overlapping expression of sprouty2 and Fgf8 is easily discernible (I-L). At 24 hours after electroporation of chick Fgf8 vector (1 µg/µl, M,N) (HH 18), Fgf8 and sprouty2 expression is widely discernible from the metencephalon to the diencephalon at the lateral side of the mesencephalon (M,N). Strong line-like expression of Fgf8 and sprouty2 along the roof plate of the mesencephalon was also seen (arrows on M and N). Misexpression of mouse Fgf8 (purple, S) and hybridization with chick Fgf8 (red, S) show that the expression along the roof plate is of the transcripts from the embryonic gene. Higher magnification figures show that sprouty2 expression is induced slightly more widely than the Fgf8 expression area (O,P). The arrowhead on O and P indicate the same point. At 24 hours after electroporation of chick Fgf8 vector at a concentration of 0.1 µg/µl, V-shaped expression of Fgf8 and sprouty2 is seen (Q,R). The right-hand-side on the dorsal view represents the experimental side. tel, telencephalon; di, diencephalon; mes, mesencephalon; is, isthmus; met, metencephalon; cont, control side; exp, experimental side. Scale bar: 200 µm.