FIGURE 3.

Visualization of FGF8, SNAII, and MYOM1 expression patterns with LNA probes. (A–C) Two LNA probes for FGF8 revealed expression in the frontonasal prominence, isthmus, future maxillomandibular and pharyngeal arch region, primitive streak, and posterior segmental plate mesoderm at HH stage 11 (A), stage 14 (B), and stage 20 (C). At stage 20 and 23, expression was also observed in the apical ectodermal ridge of the limb buds (C, two LNA probes; H, one LNA probe). Using three LNA probes for SNAII, expression pattern and intensity were similar to that obtained with an 850-nt antisense RNA probe (cf. D and E). A single LNA probe also detected SNAII expression in the intersomitic arteries at stage 15 (F) and in the neural crest at stage 11 (G). SNAII expression was also detected in the caudal wing bud at stage 23 (I) and in the interdigital webbing of the limb at stage 31 (J). Six myomesin LNAs, three from the common region and three from the EH exon, labeled dorsal and ventral muscle masses from a stage 30 wing (K) and the somitic myotome (arrowheads) and heart myocardium (arrow) at stage 19 (L). Three LNAs to the cardiac-specific EH exon labeled only the heart at stage 20 (M), whereas two skeletal-exon specific LNA probes labeled only the somite myotome in a stage 19 embryo (N).