Fig. 4. Effects of Fgf8a on down stream gene expression. Fgf8a did not affect Otx2 (A, B), Gbx2 (C,D), c-Irx2 (E,F), Pax2 (G,H), or Pax5 (I,J) expression. En 2 expression was upregulated by Fgf8a in the diencephalic region (K,L). En1 expression was also upregulated in the diencephalic region (M). Pax6 expression was repressed at the posterior diencephalon (N,O). Whole-mount in situ hybridization for Fgf8a (A,C,E,G,I, red), and for Otx2 (B), Gbx2 (D), c-Irx2 (F), Pax2 (H), Pax5 (J), En1 (M), and Pax6 (N,O), all in purple. (K,L) In situ hybridization for Fgf8a (purple) and immunohistochemistry showing En2 expression (brown). An arrow indicates the rostral limit of En2 (K), En1 (M), and Pax6 (N,O) expression, and the caudal limit of En2 (L) expression on the experimental side. An arrowhead indicates the limit of corresponding gene expression on the control side (K-O). Scale bars, 600 µm.