Fig. 1. Blocking ß1 integrin induces formation of an ectopic joint. Forelimbs of E14.5 mouse embryos cultured for 4 days were injected at the wrist with 10 µg of an irrelevant IgG (A-D) or with 10 µg of an anti-ß1 integrin mAb (E-H). (A,E) Complete limb stained with Alcian Blue/Alizarin Red to show skeletal elements. Inset shows the area in the red square. (B,F) Histological section of zeugopod region stained with Safranin O and Fast Green to show cartilage in red. (C,G) In-situ hybridizations for Wnt14. (D,H) In-situ hybridizations for Gdf5. (I) Histological sections of zeugopod region in limbs injected with 2 µg RGE peptide stained with Safranin O and Fast Green. (J) Histological sections of zeugopod region in limbs injected with 2 µg RGD peptide stained with Safranin O and Fast Green. (K,L) TUNEL assay for apoptosis, forelimbs injected at the wrist with 10 µg of an irrelevant IgG (K) or with 10 µg of an anti-ß1 integrin mAb (L).