Detection of Fgfr2b, Fgf10, and Fgf7 mRNA during palatogenesis by in situ hybridization. (A) At E12, Fgfr2b was expressed throughout the oral epithelium. (B) Fgf10 was detected in mesenchyme immediately adjacent to the epithelium in the early palatal outgrowths, the tongue, and the floor of the mouth. (D, E, G, and H) This pattern continued at E13 and E14, with Fgfr2b being strongly expressed in the epithelium of the palate and floor of the mouth. Fgf10 was mainly expressed in mesenchyme underlying the MEE and the oral epithelial surface of the palate. (D) Fgfr2b (weakly), (E) Fgf10, and (F) Fgf7 transcripts were also detected in the mesenchyme in the bend region between the palatal shelf and the cranial base (arrows) (arrowhead indicates the anterior-posterior groove between the palatal process and the body of the maxilla). (C and F) At E12 and E13 Fgf7 was mainly expressed in the palatal mesenchyme immediately adjacent to the future nasal epithelium. (I) After shelf elevation, Fgf7 was also expressed in the mesenchyme adjacent to the oral epithelium. f, floor of the mouth. All images are the same magnification; scale bar: 200 ∝m.