Fig. 2. Examination of mesoderm markers and oscillating clock genes in conditional β-catenin mutants. (A-I) Expression analysis of mesoderm and PS markers. Mox1 (orange), a somite and anterior PSM marker (A), is expressed in the E8.5 T-Cre;Ctnnb1^flLOF/ (B) and T-Cre;Ctnnb1^flGOF/+ (C) paraxial mesoderm despite the relative lack of segments. T (purple) was expressed in the node and notochord of the T-Cre;Ctnnb1^flLOF/ mutant but was absent from the PS and PSM (B). T expression, along with the first segment border B0 (black bar) (Pourquie and Tam, 2001), was anteriorized in the T-Cre;Ctnnb1^flGOF/+ streak and PSM (C). Expression of the PSM marker Tbx6 (D), and the PS marker Fgf8 (G), were similarly dependent upon β-catenin, being absent from the T-Cre;Ctnnb1^flLOF/ PSM (E,H) but upregulated and anteriorized in the T-Cre;Ctnnb1^flGOF/+ mutants (F,I). (J-S) Expression analysis of oscillating genes in the Fgf and Notch pathways. Dusp6/Mkp3, an oscillating component of the Fgf signaling pathway, is not expressed in the PSM in the absence of β-catenin (K), but is expressed in an anteriorized fashion when β-catenin is stabilized (L). Striped domains of cycling Lfng and Hes7 expression in the PSM (arrows in M,Q) were not apparent in T-Cre;Ctnnb1^flLOF/ embryos (N,R). By contrast, ectopic Lfng and Hes7 stripes were observed in the elongated T-Cre;Ctnnb1^flGOF/+ PSM (O,S). Lfng mRNA stripes were also easily detected in the T-Cre;Ctnnb1^flGOF/ mutant PSM (P). All views are lateral, with the exception of the ventral view in (P) which afforded a clear view of the Lfng stripes. Scale bars: 100 µm.