Fig. 7.

Gli3 plays a role in branchiomotor and spinal motor neuron induction. Panels A–D and I–L show dorsal views of the hindbrain, and panels E–H and M–P show lateral views of the spinal cord, with anterior to the left. (A and E) In an uninjected 36 hpf wild-type (dtr+/+ or +/−) embryo, islet antibody labeling reveals the characteristic organization of the nV neurons in r2 (asterisk), the nVII neurons (white arrowhead), and the nX neurons (black arrowhead) in the hindbrain (A), and the characteristic distribution of motor neurons (arrowhead, E) in the ventral spinal cord. (B and F) In a wild-type sibling injected with gli3 MO, the nV (asterisk), nVII (white arrowhead), and nX (black arrowhead) neurons in the hindbrain (B), and spinal motor neurons (arrowhead, F) are reduced in number. (C, D, G, and H) In an uninjected dtr mutant (C), branchiomotor neurons are essentially absent, and this phenotype is maintained in a gli3 MO-injected dtr mutant (D). In contrast, spinal motor neurons are moderately reduced in number in a gli3 MO-injected dtr mutant (arrowhead, H) compared to an uninjected dtr mutant (arrowhead, G). (I, J, M, and N) In an uninjected wild-type (yot+/+ or +/−) embryo, branchiomotor neurons are found in characteristic numbers (I; see A for details), and their numbers are moderately reduced in a gli3 MO-injected wild-type sibling (J). Similarly, spinal motor neurons are reduced in number in a gli3 MO-injected wild-type embryo (arrowhead, N) compared to an uninjected wild-type sibling (arrowhead, M). (K, L, O, P) In an uninjected yot mutant (K), most branchiomotor neurons, except nVII neurons (arrowhead), are greatly reduced in number or absent, and the number of nVII neurons is slightly decreased in a gli3 MO-injected yot mutant (L). In contrast, spinal motor neurons are greatly reduced in number in a gli3 MO-injected yot mutant (arrowhead, P) compared to an uninjected yot mutant (arrowhead, O). oto, otocyst.