Bmp expression in filiform papilla development at E14.5. In situ hybridization of Bmps (A–L) and Bmp receptors (M–P) showing expression in sagittal head sections of the anterior tongue (A, C, E, G, I, K, M, O) and the intermolar eminence (B, D, F, H, J, L, N, P) at E14.5 Bmp2 (A, B) Bmp3 (C, D) Bmp4 (E, F) Bmp5 (G, H) Bmp6 (I, J) Bmp7 (K, L) Bmpr1a (M, N) and Bmpr1a (O, P). Arrowheads indicating the circumvallate papillae (B, D, F, H, J, L, N, P). (A, B, E, F, H, I–P) Inset is high magnification view of the filiform papillae. Arrowhead indicating the boundary between epithelium and mesenchyme in inset.