A ROLE FOR BMP-4 IN THE DEVELOPMENT OF SUBCUTANEOUS CARTILAGE

BMP-4 is a transforming growth factor beta (TGF-beta) superfamily memb er which plays important roles in various developmental processes in v ertebrate embryogenesis. In this study the expression pattern of BMP-4 was examined during early chick and quail embryonic development. Tran scripts were found in the lateral ridges of the neural plate during ne urulation and in dorsal regions of the neural tube after its closure a long the whole length of the neural axis. To investigate the role of B MP-4 expressed in dorsal regions of the neural tube, cells producing B MP4 were grafted ectopically in the paraxial mesoderm in E2 chick embr yos at the level of somites 16-22. Ectopic BMP4 induced Msx-1 and Msx- 2 gene expression in superficial ectoderm and superficial mesodermal c ells which normally do not express these transcription factors. Moreov er, it could be seen that in the E9 operated embryos, additional carti lage had been induced at the level of the graft. These results suggest that BMP4 produced by dorsal regions of the neural tube acts as an en dogenous inducing signal in the activation of the genes of the Msx fam ily which are likely to be part of the cascade of molecular events lea ding to subcutaneous cartilage formation. Therefore, BMP-4 expression in the tissues located dorsally in the neural tube and superficial ect oderm is proposed to be involved in the development of the spinous pro cess of the vertebra.