Fig. 6. Hox gene expression is altered in Pbx1^–/–;Pbx2^+/– (mutant) limbs. (A) Hox gene expression (E10.25-10.5) is absent or reduced in somite-matched mutant hindlimb posterior domains before, or at, Shh onset, despite their relatively normal morphology. Open black arrowheads indicate lack of posterior expression (Hoxa9, Hoxa11, Hoxd9). Open red arrowhead indicates reduced posterior expression (Hoxd11). White arrowheads indicate absence of expression (Hoxa13, Hoxd12, Hoxd13). Diagrams depict summaries of expression data across two time-points (E10.25 and E10.5): Hox gene expression domains are represented by the same colors displayed in their respective in situ hybridization panels. Dashed domains in mutant indicate reduced Hoxd11 (pink) expression, whereas missing domains reflect complete absence of expression (Hoxa13, Hoxd12, Hoxd13). Blue domain in Hoxd diagram represents Hoxd10 expression. (B) Distal 5' Hoxa (Hoxa11 and Hoxa13) expression (E11.5) remains relatively unperturbed in mutant hindlimbs, while Hoxd (Hoxd11 and Hoxd13) expression is severely reduced anteriorly (open black arrowheads). Open red arrowheads indicate perturbed proximal posterior expression (Hoxa11 and Hoxd11). (C) 5' Hoxa (Hoxa11 and Hoxa13) expression (E11.5) remains relatively unperturbed in mutant forelimbs, whereas 5' Hoxd (Hoxd11 and Hoxd13) expression is reduced anteriorly (open black arrowheads). Proximal is leftwards; anterior is towards the top.