Gdf5 mutants N445T and N445K as well as Bmp9 cause strong chondrogenic differentiation when overexpressed in chicken limbs.

<p>Retroviral overexpression of indicated proteins after injection into chicken hind limbs at stage HH10. The contralateral hind limb was used as control. Embryos were harvested at day 7.5 and skeletal preparation stained with Alcian blue and Alizarin red. WtGdf5 lead to fusion of joints in the phalanges and metatarsals. In contrast, N445T and N455K Gdf5 as well as Bmp9 overexpression in vivo caused a severe phenotype with massive cartilage production leading to complete fusion of all skeletal elements of the limb and absence of interdigital mesenchyme. Scale: 1 mm.