Fig. 7

Met signaling is required for FMN migration. The disposition of FMNs is visualized using 48 hpf Islet1-GFP (Isl1-GFP) transgenic embryos (A–F) double labeled with GFP antibody in green (A–F) to detect branchiomotor neurons and EphA4 antibody in red (A′–F′) as a landmark of r3 and r5 to identify the position of FMNs at 48 hpf. (A–F) Dorsal confocal fluorescence images of the hindbrain in dorsal view (A–F); anterior is to the left. r6 (the final destination of all FMNs at 48 hpf) is labeled in all panels (A–F). In control embryos (A and A′), all FMNs have completed their migration and settled in r6. In contrast, in Met morphants (B and B′, Met MO, 5 mg/ml), the majority of FMNs did not complete their migration to r6 and remain in r4 and r5. In Hgf1 morphants (C and C′, Hgf1 MO, 5 mg/ml), only a few FMNs did not complete their migration, while the majority reached r6. Similarly, in Hgf2 morphants (D and D′, Hgf2 MO, 5 mg/ml), some neurons completed their migration to r6, while others failed to exit r4 and r5. Simultaneous microinjection of Hgf1 and Hgf2 MO (E and E′, each at 2.5 mg/ml) led to a higher percentage of FMNs that failed to complete their migration to r6 than when each Hgf MO was microinjected alone at 5 mg/ml (B and B′ and C and C′). In addition, microinjection of Hgf1 and Hgf2 MO (F and F′, each at 5 mg/ml) led to a more drastic migration phenotype with the majority of the FMNs failing to exit r4 and r5, a phenotype that closely resembles that observed in Met morphants (B and B′). The graph in G shows the percentage distribution of FMNs within r4, r5 and r6 for each of the conditions mentioned in (A)–(F). Scale bar, 50 μm.