Hoxa11 and Hoxd11 control early steps of chondrocyte differentiation.
Sections of E14.5 (A–C) and E16.5 (D–F) forelimbs of control (A, D), Hoxa11−/−;d11−/− (B, E) and Ulnaless embryos (C, F) were hybridized with antisense riboprobes for Fgfr3 (A–C) and Ucma (D–F). High Fgfr3 expression (A–C, yellow arrows), which demarcates columnar chondrocytes in control limbs (A), is significantly reduced in the ulna of the Hox mutants (B, C). The observed Fgfr3 expression level is comparable with the expression in round chondrocytes of the control mice (A–C, red arrows). Ucma, a marker for round cells (D, arrow), is not expressed in the majority of chondrocytes indicating that the differentiation is blocked before round and columnar chondrocytes are formed (E, F, arrows). 80x magnification; R = radius, U = ulna.