Fig. 3. Expression analysis of r5 specific marker genes. Dorsal view of wild type (A-C; G-J) and kreisler^r3/r5 embryos (D-F; K-N). (A,D) 16s embryos hybridised with Fgf3 antisense RNA showing weak ectopic activation in r3 of kreisler^r3/r5 embryos (D). (B,E) Fgf3 expression in E10.0 embryos. Ectopic transcripts can be detected in r3 and prolonged expression occurs in r5. (C,F) E10.0 embryos analysed for Krox20 expression. By this time point Krox20 expression is completely downregulated in r3 of wild-type embryos, but remains in kreisler^r3/r5 embryos. (G,K) E9.25 embryos hybridised with Hoxa3 antisense RNA. In wild-type mice, Hoxa3 is expressed up to the r4/r5 boundary (G), kreisler^r3/r5 embryos show an additional expression domain in r3 (K). (H,L) In situ hybridisation analysis using an Hoxb3 probe. In kreisler^r3/r5 mutants, Hoxb3 is ectopically activated in r3. (I,M) Activity of a lacZ reporter gene under the control of a Hoxa3 regulatory element is confined to r5 and r6 in wild-type embryos, whereas kreisler^r3/r5 embryos show additional activation in r3. (J,N) Similarly, activity of a Hoxb3 r5 enhancer is ectopically activated in r3 in kreisler^r3/r5 embryos.

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