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Fig 5. SMAD1 activation is required for cardiac-specific expression of Tbx20 in X. laevis. (A-F′) Immunohistochemistry of transverse sections through the heart of stage 40 anterior explants shows loss of nuclear phospho-SMAD1/5/8 (arrows) in the myocardium of dorsomorphin-treated explants (D-F,D′-F′) compared with DMSO-treated controls (A-C,A′-C′). In the merged images, anti-phospho-SMAD1/5/8 (pSMAD1/5/8) staining is labeled red, anti-myosin heavy chain (MHC) is labeled green, and nuclei are labeled blue with DAPI. (G-L) In situ hybridization for Tbx20 performed on stage 40 anterior and cardiac explants shows complete loss of Tbx20 expression in the heart (H,L) but not the hindbrain (J) of dorsomorphin-treated anterior and cardiac explants compared with DMSO-treated controls (G,I,K). (M-P) Whole-mount antibody staining of stage 40 anterior explants shows normal expression of the myocardial marker MHC in dorsomorphin-treated explants (N,P) compared to DMSO-treated controls (M,O). Dorso, dorsomorphin. Scale bars: 20 μm in A-F′; 1 mm in G-P. |
