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Fig. 3 kitla and kitlb Whole Mount In Situ Hybridizations(A–F) kitla mRNA expression during stages of migration. (A) kitla expression is first seen at 19 hpf in the presomitic mesoderm of the tail bud (black arrowhead). (B) Section of 19-hpf tail bud. (C) High magnification shows expression of kitla mRNA in the pineal gland at 26 hpf. (D) High magnification shows kitla mRNA in the ear at 26 hpf in the sensory epithelium, with pronounced staining in the ventral otic vesicle (black arrowhead). (E) kitla mRNA is expressed in groups of cells at the horizontal myoseptum in the middle of each somite (black arrowheads) in the trunk beginning at 22 hpf through 30 hpf (image is 26 hpf). We also observe kitla-positive cells in more dorsal locations in the posterior somites (red arrowheads). (F) Cross section of trunk shows expression near notochord at 26 hpf. (G and H) kitlb mRNA expression during stages of migration. kitlb is expressed in the ventricles of the brain (black arrowheads), in the ear (red arrow), and in the cardinal vein plexus (red arrowhead) at 24 hpf (G). Cross section of brain ventricle shows kitlb expressed in cells lining the brain ventricles (H). (I and J) kitla and kitlb mRNA expression at 4 dpf, during stage of kita-dependent survival. kitla mRNA is expressed throughout the skin (black arrowhead) and in the dorsal myotome (red arrowhead) (I). kitlb mRNA is expressed faintly in the skin (black arrowhead) (J). Scale bars: (A) 100 μm, (B) 25 μm, (C) 100 μm, (D) 50 μm, (E) 100 μm, (F) 25 μm, (G) 100 μm, (H) 10 μm, (I) 25 μm, and (J) 25 μm. nt, neural tube; nc, notochord; pm, presomitic mesoderm