Fig. 4

Lateral Speciation on Singling-out Epidermal Ionocyte Progenitors is Mediated by deltaC Ligand and notch1a/notch3 Receptors. (A) Fluorescence double in situ hybridization shows the overlapping expression between deltaC (green, left) and foxi3a (red, middle) on the epidermal ionocyte domain of the ventral ectoderm at the tail bud (tb) stage. The angles of the deltaC and foxi3a expression domain are presented as the mean±S.D. (B) The area demarcated by the dotted line in (A) is viewed at high magnification. Basically, foxi3a+ epidermal ionocyte progenitors (red) also co-express deltaC (green, asterisks). However, some deltaC+ cells outside the epidermal ionocyte domain are negative for foxi3a, suggesting that they are not epidermal ionocytes. (C–D) Fluorescent double in situ hybridization with deltaC (green) and foxi3a (red) probes to show that deltaC is transiently expressed in the epidermal ionocyte lineage. As development proceeds, deltaC is sharply downregulated in the epidermal ionocyte lineage. (E–L) Evaluation of foxi3a expression by genetic mutants or morphants with reduced or enhanced Notch activity at the tb stage. foxi3a expression in the epidermal ionocyte domain was more homogeneous in deltaC mutants of bea^tit446 (E) and bea^tw212b (F), in a notch1a mutant of des^th35b (G), and in a notch3 MO-injected des^th35b mutant (I). The foxi3a expression in the epidermal ionocyte domain was severely reduced in notch1a intracellular domain (ICD) RNA- (J) or notch3 ICD RNA-injected embryos (K). (H) notch1a/des ^th35b mutants injected with the notch1b MO showed no significant difference with uninjected mutants. N1a, notch1a; N1b, notch1b; N3, notch3; ICD, intra-cellular domain; MO, morpholino.