Myf5 is required for the forward migration of the superior oblique (so) and inferior oblique (io) primordia toward the anterior eye region. Embryos derived from the transgenic line Tg(myf5:EGFP), in which an upstream region of zebrafish myf5 was fused with enhanced green fluorescent protein (EGFP), were used to trace the migration of cranial muscle that express myf5. The primordia of io and so labeled with EGFP were clearly visible in the embryos derived from the transgenic line Tg(myf5:EGFP) at 36–48 hpf under fluorescent microscopy (A, E, I; arrows). Whole-mount in situ hybridization of wild-type zebrafish embryos showed that the expression of met, a cell marker of migration, was positive in the io and so at 36–48 hpf (B, F, J; arrows). Embryos injected with myf5-morpholino oligonucleotide (MO) and myod-MO to inhibit myf5 and myod translations, respectively, expressed met at the stages indicated. The met transcript was not expressed in the io and so of myf5 morphants (C, G, K), but met was expressed normally in the io and so of myod morphants (D, H, L; arrows). For abbreviations, see the legend of Fig. 1.
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