Fig. 2. Generalized chondrodysplasia in Bmpr1a^CKO and Bmpr1a^CKO;1b^+/- neonates. (A,B) Chondrodysplasia in Bmpr1a^CKO mice is exacerbated in Bmpr1a^CKO;1b^+/- mice. (C) Bmpr1a^CKO and Bmpr1a^CKO;1b^+/- mice exhibit multiple axial defects. (D) The dorsal arches (da) of the vertebrae are short and fail to fuse in mutants. (E,F) Forelimb (E) and hindlimb (F) defects. All long bones are shortened in Bmpr1a^CKO mice, and the scapula is hypoplastic. These defects are exacerbated in Bmpr1a^CKO;1b^+/- mice, in which the distal epiphyses of the humerus and femur are greatly reduced. f, femur; fi, fibula; h, humerus; r, radius; s, scapula; t, tibia; u, ulna; eo, exoccipital bone; so, supraoccipital bone; C1, first cervical vertebra.