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Figure 2. Hh/Gli Signaling Is Required for Respiratory Wnt-Mediated Specification in Xenopus
(A) Schematic of a section through the lung field showing a model of Hh/Gli regulation of Wnt/BMP-mediated respiratory induction.
(B) In situ hybridization and immunostaining of foregut sections from NF34 stage control and Hh/Gli-deficient Xenopus embryos generated by either Gli2+Gli3-MO injection or cyclopamine treatment from NF20–34. Expression of the lung-inducing wnt2/2b and bmp4 ligands and Nkx2-1+ respiratory specification requires Hh/Gli signaling, which can be rescued by injection of a human Gli2 mRNA. Foxf1+ lpm and nuclear pSmad1/5/8 are also reduced in Hh-deficient embryos. The scale bar represents 50 μM.
(C) Expression of ptch1 and wnt2b are activated in mesoderm explants treated with the Hh-pathway agonist SAG from NF20–34.
(D) Activation of β-catenin by Bio treatment from NF28–34 rescued and expanded (bracket) the nkx2-1 respiratory domain in Gli2+3 MO-injected embryos, indicating that Hh signaling acts upstream of Wnt. The red arrow indicated absent nkx2-1 expression. See also Figure S2. |
