Fig. 8

Gli2 expression is affected in the forebrain, but not in the hindbrain, of Hh pathway mutants. All panels show cross sections of the neural tube at the indicated axial levels, with dorsal at the top. Embryos were processed for islet1 (purple); gli2 (red) (A–D, G–J) or nk2.2 (purple); gli2 (red) (E, F) two-color in situs. (A–D) In r4 of a wild-type embryo (A), islet1-expressing motor neurons (arrowhead) are located just ventral to the gli2 expression domain. Similarly, the few islet1-expressing neurons in yot mutants (arrowhead) are located ventral to the gli2 expression domain (B), and gli2 expression does not extend into the ventral-most neural tube in dtr (C) and smu (D) mutants. (E and F) In r5, while nk2.2-expressing cells (arrowhead) are found immediately adjacent to the floor plate and notochord (arrow) in a wild-type embryo (E), nk2.2 expression is absent in yot mutants (F), but the gli2 expression domain does not expand ventrally. (G–J) At the forebrain level, the islet1-expressing epiphysial neurons (arrowhead) are located at the roof of the neural tube. In a 21-hpf wild-type embryo (G), gli2 expression is limited to the dorsal two-thirds of the neural tube (bracket). In contrast, in yot^ty119 (H), dtr^te370 (I), and smu^b641 (J) mutants, the gli2 expression domain is expanded ventrally to different extents (brackets).