Fig. 1. Loss- and gain-of ß-catenin activity in limb mesenchyme causes truncations of the limbs. (A-C) Normal wild-type limbs (A), and limb truncations in lof ß-cat^Prx1/- (B) and gof ß-cat^ex3Prx1/+ (C) E16.5 embryos. (D-G) In situ hybridization for ß-catenin using the mß-catenin-del probe. (D) Strong ubiquitous expression in flank and limb mesenchyme, and in the ectoderm and AER of wild-type E10.5 limbs. (E) Loss of ß-catenin expression at E10.5 in flank (black arrow) and forelimb (red arrow) mesenchyme in ß-cat^Prx1/- embryos. (F) Less deletion is detected in E10.5 ß-cat^Prx1/- hindlimbs (HL, red arrow). (G) Near complete loss of ß-catenin expression in the mesenchyme of ß-cat^Prx1/- E11.5 forelimbs, while ectodermal expression remains normal.