Morphological phenotype of Oot embryo. The drawings show dorsal views (rostral to the top) of the optic tectum (ot), isthmicregion (ir), cerebellum (ce), and the fourth ventricle (v). Histological features are shown in the frontal (dorsal to the top) and horizontal (rostral to the top) sections. Thick arrows indicate the abnormal invagination in the Oot mutant. The broken lines show the boundary between the caudalmost midbrain (cm) and the rostralmost hindbrain (rh). Scale bars, 50 um.
Isthmic gene expressions from stages 21 to 26. Dorsal (a, a', b, b', e-j, e'-j', rostral to the top) and left lateral (c, c', rostral to the left) views of in situ hybridization specimens, and their sections are shown. The insets in c and c' show dorsorostral views (thick arrows) of the specimens. Peri-midline cells in the dorsal domain (dd) are fgf8-negative on one side in the mutant (asterisks). In the mutant, the fgf8 expression is asymmetrical (arrowheads). Broken lines show the tectum/cerebellum boundary. ce, cerebellum; ir, isthmus; ot, tectum; v, the fourth ventricle. a-e, a'-e': scale bars, 25 um. f-j, f'-j': scale bars, 50 um. Panels c, e, and h-j are modified from Ishikawa et al. (2008), with consent from the Zoological Society of Japan.