Fig. 4. Pbx1 and Pbx2 mesenchymal expression in later limb development is dynamic and, in part, complementary. (A,B) At E9.5-10.75, Pbx1 is expressed in proximal forelimbs and hindlimbs, mostly anteriorly, whereas Pbx2 is expressed distally and throughout the limb. At E11-11.75, Pbx1 is still expressed proximally in limbs, but localized anteriorly and posteriorly in the mesenchyme proximal to the autopod. Similarly, Pbx2 expression becomes restricted to this domain, albeit more broadly. (C) Diagrams depicting dynamic expression of Pbx1, Pbx2 and overlapping domains of Pbx1/Pbx2 at different gestational days. These schemes represent summaries of the expression patterns present at the gestational time-points indicated by the somite range at the top of each panel. Proximal is leftwards, anterior towards the top. som, somites.