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Fig. 1 Expression of plxna4 mRNA by hindbrain cells. ISH for plxna4 in lateral whole mount (A, B, D, G) and in transverse sections (C, E, F, H, I, K), along with JL8 immunolabel for GFP in whole mount (J) and section (K′) of Tg(islet:eGFP) fish. (A) At 18 ss, plxna4 is expressed in the forebrain and spinal cord. (B) plxna4 expression at 24 hpf. Otic vesicle (arrowhead). (C) Transverse hindbrain section shows two lateral domains of plxna4 expression (arrows), a broad dorsal domain (arrowhead), as well as expression by cells adjacent to the floorplate. Approximate location of section is shown by line (C) in B. (D, G) plxna4 expression at 36 hpf (D) and 48 hpf (G). (E, F, H, I) plxna4 mRNA in bilateral cell populations (arrowheads) at 36 hpf (E, F) and 48 hpf (H, I). plxna4-expressing cells also abut the floorplate (arrows). Approximate location of sections are shown by lines in D (for E and F) and G (for H and I). Inset in I shows Islet immunolabeling in a comparable hindbrain section. (J) plxna4 mRNA in the hindbrain and in some Islet1-expressing (teal) cranial motoneurons (arrowheads) at 24 hpf. (K) plxna4 expression (K) and JL8 immunolabeling for GFP (K′) in a 48 hpf hindbrain section. Dotted line marks the pial surface and arrows point to co-expressing cells. a: anterior, br: brain, d: dorsal, floor plate: fp, fb: forebrain, hb: hindbrain, mb: midbrain, ov: otic vesicle; p: posterior, v: ventral, ve: ventricle. Scale bar: 300 μm (A), 250 μm (B, D, G), 200 μm (J), 50 μm (C, E, F, H, I), 25 μm (K, K′).