Expression domains of nrarp a and nrarp b in wild-type embryos as shown by whole mount in situ hybridization. (A–D) Expression pattern of nrarp a: at 30% epiboly: (A) animal pole view; (B) optical section, lateral view; (C) at shield stage, lateral view; and (D) 90% epiboly, vegetal view, dorsal to the top. (E–H) Comparison of nrarp a and b expression pattern at tail bud stage: (E, F) dorsal (G, H) lateral view. Notice complementary patterns in the highest domains both genes (red arrows). (I, J) nrarp a expression at 3 somite stage, (I) dorsal (J) lateral view. (K) Double in situ staining with probes for nrarp a (blue) and mesp b (red). Notice overlapping domains in anterior part of somite primodia S-1 and S-2. (L, M) Expression of nrarp a and b presented in flat mounted embryos at 8 somite stage. (N–R) Double in situ hybridization with probes for pax2a and nrarp a (N, P) and (P, R) nrarp b in flat mounted embryos. Notice more superficial layer with presumptive precursors of sensory neurons (green arrow) and deeper located presumptive motoneurons (orange arrow). Abbreviations: ep, epiboly; ov, otic vesicle; psm, presomitic mesoderm; r, rhombomers; and s, somite.

Expression pattern of nrarp a and b in 1 day old wild-type embryos and altered expression in mutants at 11 somite stage shown by in situ hybridization. Lateral (A, B) and (C) dorsal view of flat mounted embryos. (D–G) Expression of nrarp a at 11 somite stage in (D) wild type embryos; (E) mib; (F) ace; and (G) aei. (H, I) Expression of nrarp b in wild type embryos (H) and (I) mib. (J–K) Higher magnification of PSM region in the same mutants (red arrows indicate nrarp a expression in the anterior part of somite primodia in wild type) (J) and (K) ace (L) aei and (M) mib. Abbreviations: fb, forebrain; hb, hindbrain; mb, midbrain; and mhb, midbrain-hindbrain boundary.