Fig. 2. Dorsoventral patterning is altered by loss or gain of BMP function. Alternate sections of (A-C) control uninfected stage 20 limb, (D-G) Noggin-infected stage 20 limb and (H-K) constitutively activated BmpRIB-infected stage 19 limb. Noggin misexpression results in dorsalized limbs due to loss of EN1 and ectopic Wnt7a and Lmx1 expression on the ventral side (marked by asterisks in D-F), whereas constitutively activated BmpRIB misexpression ventralizes the limb because of EN1 misexpression and downregulation of Wnt7a and Lmx1 on the dorsal side (marked by + in H-J). Note that in H-K, there is no morphological AER. (G,K) Anti-GAG antibody to reveal virus distribution. (L-M) Whole-mount double RNA in situ hybridization for Fgf8 in the AER and Shh in the mesenchyme. (L) Control, (M) Noggin-infected, (N) Lmx1-infected stage 24 limbs. The white line marks the midline of the AER and the DV interface. After dorsalization of the limbs due to misexpression of Noggin or Lmx1, Shh expression is ventrally expanded.
