Fig. 4. Skeletal defects observed in Bmp4^lacZ/+ mice are not present in Bmp4^S2G/S2G mice. (A,B) Alcian Blue-stained E15.5 limbs. A postaxial cartilaginous element is indicated with an asterisk. (C-F) Dorsal views of skeletal preparations of cervical (C,D) and thoracic (E,F) vertebrae from adults. Yellow arrowheads mark vertebrae that have not fused and/or formed a dorsal spinous process. Black arrows indicate the 13th rib.