Fig. 6. Disrupted AER maturation and reduced Fgf10 expression in T^-/- embryos. Comparison of Fgf8 (A-E), Bmp4 (F-J), En1 (K-O), Wnt7a (P-S) and Fgf10 (T-X) expression in wild-type (wt, left sides) and T^-/- (right sides) embryos at different stages as indicated to the left of each row by age and average somite (so) number in wild type. As indicated in the upper left corner, limb buds shown in each panel are oriented with dorsal to ventral axis (dv) from left to right, and with anterior to posterior axis (ap) from top to bottom of the panel. The small arrows highlight some of the focal gaps, irregularities, and wavy borders in pre-AER or AER zone revealed by marker expression patterns in T^-/- limb buds. Note that T^-/- embryos showed mottled early pre-AER expression (A,F) and later broad, weak, and irregular patterns of AER markers compared to very sharply demarcated expression in the wild type. Fgf10 expression was substantially decreased by E9.5 and later (V-X). Note some T^-/- limb buds were very irregularly shaped (eg. Q,T,V). Hybridization signals at various expression sites unaffected by loss of T (e.g. craniofacial, branchial arch, gut) were similar in T^-/- and wild-type embryos, serving as internal controls (data not shown).