Fig. 2. Effects of Fgf8a misexpression. (A) Dorsal view of the E7.5 chick brain. Misexpression of Fgf8a enlarged the tectum (compare control side and the experimental side). In A-C the anterior limit of the tectum is indicated by white arrowheads and a black arrow (in B) on the control side, and by black arrowheads on the experimental side. (B) Horizontal section showing that the tectum has enlarged into the diencephalic territory. (C) Tectal swelling extended towards anterior at E3.5. (D,E) Whole-mount immunohistochemistry with anti-neurofilament antibody of an E3.5 embryo. On the control side, oculomotor (III) and trigeminal (V) nerves are present. On the experimental side (E), there are 3 nerve trunks that run similarly to the oculomotor nerve (arrowheads). The arrow indicates the oculomotor nerve on the control side. (F) Immunohistochemistry with anti-Islet1 antibody of an E3.5 embryo to show the motor nuclei. On the control side the oculomotor nucleus (III) at the mesencephalon and the trochlear nucleus (IV) at the isthmus are clearly visible. On the experimental side the oculomotor nucleus extends anteriorly into the diencephalic territory (arrowheads). cont: control side; exp: experimental side, tel: telencephalon, di: diencephalon, tect: tectum, mes: mesencephalon. Scale bars, 4 mm (A, B), 800 µm (C), 400 µm (D, E) and 200 µm (F).