Fig. 4. ß-catenin is required for Myf5 activation in somite explants. (A-D) ß-catenin^{floxdel/floxed} somite explants were infected with a lentiviral vector carrying the cDNA for GFP (A,B) or CRE-IRES-GFP (C,D), and co-cultured with neural tube. Infected cells were visualized by GFP fluorescence (B,D) and Myf5-expressing cells were visualized with an anti-Myf5 monoclonal antibody (A,C). The GFP⁺ cells were also Cre⁺ when tested with an anti-Cre antibody (data not shown). (E) The absence of ß-catenin in Cre-infected explants was demonstrated by PCR with specific oligonucleotides discriminating between the floxed and floxdel allele of ß-catenin (Brault et al., 2001). (F) Quantification of Myf5 activation. Independent experiments (n=8) were performed in triplicate and averaged.