Fig. 6. Persistent identity changes detected by altered expression of Met and Cad8 in wild-type and mutant hindbrains. (A,B) Ventricular views of Met expression in wild-type (A) and Hoxb1 (B) mutant flat-mounted hindbrains at 12.5 dpc. In the wild type, Met was expressed in the Vm trigeminal (A, arrowhead) and the superior salivatory nucleus (A, bracket) only. In the Hoxb1 mutants, there were ectopic nuclei expressing Met (B, asterisks). Note also the reduction of the superior salivatory nucleus (B, brackets). (C-H) Pial views of Cad8 expression in wild type (C,F), Hoxa1 (D,G) and Hoxb1 (E,H) flat-mounted hindbrains at 12.5 dpc (C-E) and 13.5 dpc (F-H). In wild-type hindbrains, Cad8 was expressed in the ventral half or r1, r2 and r3 (C,F) and in the VIIm (C,F, black arrowheads) at 12.5 and 13.5 dpc. At 12.5 dpc, there was a longitudinal stripe of Cad8 expression adjacent to the floor plate of r1 and r2, which extended into r3 at 13.5 dpc (C,F vertical bars). In Hoxa1 mutants, r3 expanded caudally in both 12.5 (D) and 13.5 (G) dpc (compare the vertical bar in D with C, and in G with F), and VIIm were barely detectable only at 13.5 dpc. In Hoxb1 mutants, Cad8 was ectopically expressed in r4 in a pattern reminiscent of r2 (E, r4*) at both 12.5 (E) and 13.5 (H) dpc, but no VIIm could be detected in either stage (E,H, white arrowheads).

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