Fig. 4. Post-otic neural crest cell alterations in RA-rescued Raldh2^–/– embryos. (A-D) Whole-mount in situ analysis of EphA4 (A,B) and EphA2 (C,D) transcripts in E9.5 wild-type (A,C) and Raldh2^–/– (B,D) embryos. In (D), EphA2-labeled cells are confined dorsally to the foregut pocket (arrowhead). E-I, Distribution of Crabp1 transcripts in E9.5 wild-type (E,H) and Raldh2^–/– (F,G,I) embryos. (E-G) Profile and (H,I) dorsal views. Brackets in F,G delineate the mutant post-otic NCC populations (which normally would colonize the 3rd, 4th and 6th branchial arches). An asterisk in G indicates cells that are abnormally confined along the dorsal foregut wall, and may correspond in part to pre-otic (r4-derived) NCC. Mutant embryos also exhibit abnormal patterns of connectivity between the post-otic hindbrain and NCCs (arrowheads and bracket in H and I, respectively). b1-b6, branchial arches; fg, foregut; fl, forelimb bud; ot, otocyst; p1-p3, pharyngeal pouches; r3-r6, rhombomeres.