Figure 4
Expression of Ltbps in the developing limb. (A-F) Expression and regulation of Ltbp-1. (A) Whole mount in situ hybridization of Ltbp-1 gene showing intense labeling in the apical ectodermal ridge of the developing leg bud at stage HH20. (B-C) Whole-mount in situ hybridizations showing the expression of Ltbp-1 at stage HH24. Note that in addition to the AER domain, expression is also observed in the dorsal surface of the limb bud (arrows). (D) Image shows a dramatic down-regulation of Ltbp1 in the AER eight hours after the application of a BMP7- bead in the progress zone mesoderm (arrow). Compare the absence of labeling in the treated left limb with respect to the contralateral untreated control. (E) Whole mount in situ hybridization showing a more moderate downregulation of Fgf8 in the AER in a limb bud subjected to the same treatment to that shown in D (arrow shows the position of the BMP-bead). (F) Whole mount in situ hybridization showing the expression of Ltbp1 in the developing digits at stage HH26. (G-I) Expression of Ltbp2 in early (stage HH20; G) and late stages of limb development (stages HH30 and HH32; H and I). Note the expression domain in the AER of early limb buds (arrow in G) and the domains of the developing interphalangeal joints at the stages of digit morphogenesis (arrowheads in H and I).