iro3 is expressed in CaP and VaP motoneurons. iro3 in situ hybridization (A,B,D,E,G,H) and Islet antibody staining + iro3 in situ hybridization (C,F,I). iro3 staining is blue and cytoplasmic; Islet antibody staining is brown and nuclear. Lateral views of the trunk at 6-8 somites (A), 10-12 somites (B), 18-20 somites (C-F), and cross-sections through the trunk at 18-20 somites (G-I). A-D,F,G,I: iro3 expression in wild-type (wt) embryos. E,H: iro3 expression in mib mutants. At all of these stages, in wild-type embryos, iro3 is expressed in a broad domain in intermediate spinal cord and in a subset of primary motoneurons (CaPs and VaPs). Arrows indicate iro3-expressing primary motoneurons (all of the iro3-expressing PMNs are indicated in A, C, and F, but only examples are indicated in B, D, E, and G-I); stars indicate primary motoneurons that do not yet express iro3 (MiPs and RoPs, brown only cells). The dotted lines in B demarcate somite boundaries. F is a close up of a two-somite length of the embryo shown in C. In mib mutants, the broad intermediate domain of iro3 expression is lost but additional cells in the primary motoneuron domain express iro3. Scale bar in A = 50 μm in A-E,G-I, 25 μm in F.
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