FGF signaling is essential for maintenance but not initial transcription of β-catenin-induced boz RNA. (A-H) FGF signaling is essential for accumulation of β-catenin-dependent boz, but not sqt, expression at 4 hpf. Neither boz nor sqt is expressed in ichabod embryos (A,E), but expression of both genes is restored by injection of β-catenin RNA (B,F). sqt but not boz transcript is expressed in ichabod embryos co-injected with XFD and β-catenin RNAs (C,G), whereas both genes are expressed in embryos co-injected with d50 RNA(D,H). (I-Q) Inhibition of FGF signaling does not affect the initial appearance of boz transcript but affects its maintenance. β-catenin-induced boz transcript can be detected in ichabod embryos at 3, 3.5 and 4.0 hpf (J,M,P), but MKP3 inhibition of FGF signaling results in absence of detectable β-catenin-induced boz RNA at 3.5 and 4.0 hpf (N,Q), although the amount at 3.0 hpf is not reduced (K). (R,S) MKP3 also can inhibit boz RNA accumulation in wild-type embryos. All embryos are shown in animal pole view.
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