Immunofluorescent staining of down-stream mediators of transforming growth factor α (TGF-β)/bone morphogenetic protein (BMP) signaling pathway in the developing palate at E13.5. a, b pSmad1/5/8; c, d pSmad2/3; e, f Smad4; g, h pP38. a, c, e, g Anterior palate; b, d, f, h posterior palate. White lines demarcate the palatal region for quantifying the immunofluorescence intensity (T tongue, PS palatal shelf). Bars 50 μm. h Statistical comparison of immunofluorescence intensity. *P < 0.05, **P < 0.01