Fig. 5

 Hindbrain expression of zebrafish insm1a (A, C, E, G, and I) and insm1b (B, D, F, H, and J). Rhombomeres 3 and 5 are marked by egr2b (A–D) or ephA4a (E–J) expression (red). All panels are shown with anterior to the left in ventral (A, B, E, F, I, and J) or mediolateral (C, D, G, and H) focal planes. Scale bars represent 50 μm. At 14 hpf (A and B) insm1a and insm1b are seen in rhombomeres 2 and 4. At 18 hpf (C and D), insm1a becomes more prevalent in the ventral hindbrain while insm1b is fairly dispersed. During pharyngula stages (32 hpf; E–H) insm1a expression is dominant adjacent to the midline and insm1b in the cranial ganglia. Alternating large and small gaps representing rhombomeres and rhombomere boundaries, respectively, are seen in r1 through r6. By 48 hpf (I and J) both insm1a and insm1b occupy a dorsoventral plane that extends laterally, directly adjacent to rhombomere boundaries (arrows). However, this plane does not extend entirely to the edge of the rhombomere, instead it converges within a rhombomere to form a funnel-shape (asterisk) between posterior and anterior segments of adjacent rhombomeres. There is considerable expression of insm1a adjacent to the midline (arrowhead). For lateral views tissues surrounding the hindbrain were removed for clarity. Note that the majority of egr2b or ephA4a staining is dorsal (seen in C and D) which results in a blurred boundary in the ventral focal planes shown. cb, cerebellum; ot, otic vesicle; and r, rhombomere.