Fig. 2. Expression patterns of Tcf/Lef family members, ß-catenin and Gli1 in the PSM and newly formed somites at E9.5. (A) Lateral view of a lightly stained Lef1 whole-mount in situ hybridized embryo after OPT scanning and 3D reconstructions. (B,C) Optical sections through the resulting reconstruction: B is through the tail region, in the same plane of view as A, C is a transverse section, as indicated by the line in A. (D) An embryo hybridized to reveal Tcf3 expression in the newly formed somites. (E) Transverse section through the newly formed somites shown in D. (F) A similar section to C, through a Tcf1 hybridized embryo. (G) ß-catenin WHISH; arrowheads indicate expression in the lateral mesoderm. (H,I) BAT-gal transgenic reporter mice: (H) ß-galactosidase staining, (I) lacZ WHISH. (J,K) Transverse sections through newly formed somites in I and H, respectively. (L) A similar section to in J and K, immunostained for ß-catenin. (M) Gli1 WHISH. (N,O) Transverse sections through PSM (N) and newly formed somites (O) in M.