Skeletal preparations of the HLs of single and combined <i>Msx;Dlx</i> mutant animals.

<p>Chondroskeletal preparation of the HLs of E14.5 embryos (micrographs on the left) and full skeletal preparation on newborn animals (micrographs on the right), representing single and combined <i>Dlx</i>;<i>Msx</i> mutant genotypes (indicated on the left). The HLs of <i>Msx2</i>^+/−;<i>Dlx5;Dlx6</i> DKO animals (E,F) display an aggravated ectrodactyly phenotype compared to <i>Dlx5;Dlx6</i> DKO ones (C,D), with fusion of the external digit (1with 2, 4 with 5) and hypoplasia of the central digit. <i>Msx2</i>;<i>Dlx5</i>;<i>Dlx6</i> TKO HLs (G,H) display a further aggravated ectrodactyly phenotype, with the external digits fused and extended towards the opposite (anterior-posterior) sides, and a complete absence of the central digit. The limbs of <i>Msx1^+/−;Dlx5;Dlx6</i> DKO mice (not shown) show ectrodactyly similar to that observed in <i>Dlx5;Dlx6</i> DKO mice, whereas <i>Msx1;Dlx5;Dlx6</i> TKO mice (I,J) show ectrodactyly and loss of skeletal elements deriving from the anterior mesoderm of the autopod and zeugopod, a phenotype seen in <i>Msx1;Msx2</i> DKO mutant embryos (K). The stylopod shows no evident defects. The anterior-posterior orientation is shown. The numbers 1–5 indicate the digits (1 is the toe). Asterisks indicate hypoplasia or absence of skeletal structures. The drawings on the left schematically illustrate the Dlx-related (red elements) and the Msx-related (purple elements) skeletal defects, corresponding to the genotypes examined.