CONTROL OF DORSOVENTRAL PATTERNING OF SOMITIC DERIVATIVES BY NOTOCHORD AND FLOOR PLATE

We have examined the effect of implantation of a supernumerary notocho rd or floor plate on dorsoventral somitic organization. We show that n otochord and floor plate are able to inhibit the differentiation of th e dorsal somitic derivatives-i.e., axial muscles and dermis-thus conve rting the entire somite into cartilage, which normally arises only fro m its ventral part. We infer from these results that the dorsoventral patterning of somitic derivatives is controlled by signals provided by ventral axial structures.