Fig. 5. AMO-injected embryos show inhibition of DiI-labeled neural crest migration. Both blastomeres of two-cell stage embryos were injected with AMO, allowed to develop to stage 16, and then injected with the lipophilic dye DiI into the dorsal neural folds in the area of the hindbrain, containing presumptive cranial neural crest cells (A). Upon reaching stage 34, the embryos were examined under a fluorescent stereoscope. (B) In control embryos injected only with DiI, fluorescent cells are observed around the branchial arches (arrow), a target for cranial neural crest cells (in 44/51=86% of embryos). By contrast, in AMO-injected embryos (C), DiI-labeled crest cells remain in the dorsal aspect of the neural tube (arrow; in 31/43=72% of embryos; n=3). In a different set of experiments (D), a single blastomere of two-cell stage embryos was injected with AMO along with GFP RNA, used as a lineage tracer. Embryos were allowed to develop to stage 16 and were then injected with DiI on both the right and left sides of the dorsal neural folds, in the same area of the hindbrain as in A. Upon reaching stage 28, embryos were examined under a fluorescent stereoscope. On the untreated side (E), streams of cells (arrow) migrating from the site of injection ventrally, towards the branchial arches, are observed (in 68/68=100% of embryos). On the AMO/GFP-treated side (F), DiI-labeled cells are observed above the neural tube (arrow), and no fluorescence is detected in or around the branchial arches (in 49/68=72% of embryos; n=3).

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