Distinct roles for gli genes in pituitary patterning. (A) To block Gli function at later time periods, 17.5 hpf embryos were placed in agarose wells and antisense oligonucleotides were injected into the space below the developing head. (B, C) Late injection of gli3 MOs led to an expansion of ptc1 into the dorsal spinal cord (arrows, spinal cord shown in cross section), consistent with a loss of Gli3 repressor function. This control experiment shows that Gli activity can be reduced by late MO injections. (D) Normal expression of nkx2.2a and prl (inset, ventral view) following control MO injection at 17.5 hpf. (E) Injection of gli1 MOs reduced anterior expression of both nkx2.2a and prl (inset). (F, G) Late injections of gli2a or gli2b antisense MOs or S-oligos led to a posterior expansion of nkx2.2a expression in the placode (arrowheads). (H) Lateral view of the ventral forebrain showing normal prl (blue label) and pomc (red) expression in the placode of control MO injected embryos. (I, J) Late injection of gli2a or gli2b MOs led to ectopic prl expression in the posterior region of the placode (arrowheads), and to a reduction in posterior pomc expression. (D–J) show 40 hpf embryos, anterior to the left. Black lines show the anterior–posterior extent of the placode with the arrowhead pointing to the most posterior extent of gene expression (nkx2.2a or prl). Dotted lines in D, E insets outline the adenohypophysis. Scale bar: B, C; 20 μm, D-J; 35 μm.
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