Fig. 6. Expression of Fgf8, Fgf4 and Gre in ozd limb buds. (A,B) Fgf8 is expressed at high level throughout the ozd AER. The AP extent of the AER is reduced in the narrowed ozd limb. (C) At st. 27, Fgf8 appears down regulated in the anterior AER but expression persists at high levels in the posterior AER. (D,E) Fgf4 expression in the mutant AER is reduced except at the most posterior edge, where a spot of elevated expression became apparent by st. 23. Note that the specimens in D and E have been analyzed for both Fgf4 and Shh expression. (F) By st. 25, Fgf4 expression has declined in the mutant AER except for the posterior spot of high-level expression. (G-I) Gre expression in ozd and wild-type limbs. ozd limb buds express Gre but, contrary to normal, its spatial domain of expression expands to the posterior border. In all the panels anterior is up.