PERTURBATION OF BMP SIGNALING IN SOMITOGENESIS RESULTED IN VERTEBRAL AND RIB MALFORMATIONS IN THE AXIAL SKELETAL FORMATION

Axial skeletons such as vertebrae, ribs, and scapulae develop from the embryonic semitic mesoderm through interactions with neural tube/noto chord and skin ectoderm. Bone morphogenetic proteins (BMPs) seem to pl ay important roles in these tissue interactions; however, the relation ship between BMP signaling and the early development of axial skeleton s is poorly understood, In this report, we investigated possible roles of BMP signaling in axial skeletal formation, First, we describe the expression patterns of BMP4 and type I receptors for BMP during somito genesis in chick embryos based on whole mount in situ hybridization. N ext, the effects of BMP on axial skeletal morphogenesis were investiga ted by implantation of BMP proteins into the dorsal mesoderm at the ti me of somitogenesis. Transcripts for both BMP4 Ligand and its receptor s are expressed in the dorsal ectoderm and mesoderm, Implantation of B MP4 and BMP2 into the dorsal regions of embryos result in subsequent a nomalies of vertebrae, ribs, and scapulae, The effects of BMP implanta tion on the skeleton are shown to be dependent upon the semitic stage, Vertebral anomalies are restricted to the dorsolateral elements of th e vertebrae and specifically observed after BMP implantation into embr yonic day 2 (E2) embryos, but not E3 embryos, These results indicate t hat implantation of BMP into the dorsal part of embryos where endogeno us BMP ligand and BMP receptors are expressed perturbs BMP signaling a nd causes axial skeletal malformations, The findings presented here su ggest that BMP signaling may be involved in the early developmental pr ocess of the axial skeleton.