Fig. 2

Morphological defects of prep1.2 morphant embryos. A: Schematic design of antisense morpholinos and prep1.2-GFP construct. The morpholinos are complementary to 25 bp in the 5′ region spanning the ATG (MO1-prep1.2) or to 25 bp in the 5′UTR region (MO2-prep1.2); MO2-prep1.2 is non-overlapping with the 5′UTR of the prep1.2-GFP mRNA injected and can only block endogenous prep1.2 mRNA. Two control morpholino oligos were designed. They are mutated in 5 (MO1-prep1.2-5MIS) or 6 (MO2-prep1.2-6MIS) positions. B, C: Each prep1.2 morpholino was co-injected with prep1.2-GFP mRNA to test its specificity; only MO1-prep1.2 blocks prep1.2-GFP translation in injected embryos (compare C with control morpholino in B) as revealed by the GFP signal in cell nuclei of the head region. D, E; day 5 larvae injected with MO1-prep1.2 display morphological defects: lack of branchial tissue, impaired jaw organization, absence of pectoral fins and pigmentation defects. F–I; Alcian blue staining of 5-day-old larvae shows that Mekel′s cartilage is normal while hyoid cartilage was misshaped and reduced in size. Morphant embryos also display a reduction of the third pharyngeal cartilage while the more posterior ones are completely absent. ba: branchial arches; pf: pectoral fin; cb: ceratobranchial; ch: ceratohyal; e: ethmoid plate; me: Meckel′s cartilage; tr: trabeculae cranii. D and E: Embryos are in dorsal view. F and G: Embryos are in ventral view. H and I: embryos are in lateral view.