Fig. 5. Temporal regulation of Ihh expression by Wnt9a signaling. In situ hybridization on serial sections showing the humerus region of wild-type and Wnt9a^-/- littermates. (A-D) Ihh expression at E11.5, E12.5, E13.5 and E14.5 in wild-type and Wnt9a^-/-; showing no significant difference at E11.5 (A), downregulation of Ihh expression at E12.5 (B) and E13.5 (C), and delayed separation of the Ihh expression domains at E14.5 (D) in Wnt9a^-/- humeri. (E) Size reduction of the Ppr expression domain in Wnt9a^-/- humeri compared with wild type at E13.5. (F) Increased Col10a1 expression domain at E12.5 in Wnt9a^-/- humeri. (G) Strongly reduced Col10a1 expression domain at E13.5 and E14.5 (H) in Wnt9a^-/- humeri. Reduced expression levels of Ptch1 in chondrocytes and perichondrium (I), of Pthrp in the articular region (shoulder joint) (J), and of Runx2 (K) and Osx (L) in the perichondrium/periosteum.