Fig. 5. WNT3a and FGF8b induce T expression in primary limb mesenchyme culture. Mesenchymal cells were dissociated from stage 19/20 chick embryo limb buds and used immediately. RNA from cells infected with Wnt3a-expressing retrovirus (Wnt3a-RV), control viral vector (RV), uninfected control (uninf.) or after treatment with either heparin sulphate (hs) alone or with recombinant FGF8b+hs (FGF-8b) were harvested at times indicated and hybridized with a chick T 3'-UTR probe (Ch-T), followed by a chick ß-actin probe to control for loading. RNA extracted from stage 18 chick tail bud was included as a positive control. Both WNT3a and FGF8b induced T expression within 18 hours and activation by FGF8b protein was detectable by 8 hours. FGF4 protein had no effect on T expression at either time (data not shown).