Fig. 5. Changes in BMP signaling alter Msx expression. (A-F) Constitutively activated BmpRIB misexpression induces ectopic Msx2 and Msx1 expression in dorsal ectoderm (B,D,F) compared with uninfected limbs (A,C,E). Asterisks in F highlight ectopic Msx1 expression in dorsal ectoderm. (G-J) Noggin misexpression represses Msx expression (H,J) compared with uninfected limbs (G,I). (H) Msx1 is not expressed in the hindlimb in either the ectoderm or mesenchyme, whereas, in this sample, it is still detected in the forelimb. (J) Msx2 is not expressed in the forelimb, hindlimb and flank ectoderm or mesenchyme. (A,B) Stage 24 forelimbs shown in whole-mount; (C,D) stage 19 and (E,F) late stage 20 forelimbs shown in section. (G,H) Stage 18 (37 somite) embryos; (I, J) stage 17 (32 somite) embryos.