Fig. 8. Sox8mo-injected embryos have defects in neural crest migration. (A) Phosphohistone H3 immunostaining (-pH3) shows no difference in the pattern of cell proliferation in stage 17 embryos that received unilateral injection of Sox8mo (left side; FITC label) when compared with the uninjected side. (B) TUNEL staining shows no difference in the pattern of cell death in stage 17 embryos that received unilateral injection of Sox8mo (left side; FITC label) when compared with the uninjected side. In A,B, embryos are viewed from the dorsal side, anterior towards the top. (C) The migration of cranial neural crest cells into the pharyngeal arches visualized by Sox9 and Sox10 expression is severely perturbed in Sox8-depleted embryos (brackets). These cells appear to accumulate lateral to the hindbrain. RNA encoding the lineage tracer ß-galactosidase was co-injected to identify the injected side (red staining). Embryos are viewed from the lateral side, anterior towards the left (left panels) or anterior towards the right (right panels). (D) Tissue section of Sox8mo-injected embryos showing accumulation of Sox10-positive cells (small bracket; outlined in red) lateral to the hindbrain on the injected side (arrow); on the control side, Sox10-positive cells have initiated their migration (large bracket; outlined in red). The black outline indicates the position of the hindbrain (hb). (E) TUNEL staining of a stage 25 embryo that received unilateral injection of Sox8mo (left panel; dorsal view, anterior to top). The injected side (arrow) is characterized by reduced pharyngeal arches. Higher power views of the cranial regions on the injected side show no significant increase in TUNEL-positive cells (right panel; lateral view, anterior towards left, dorsal towards top) when compared with the uninjected side (middle panel; lateral view, anterior towards the right, dorsal towards the top).