Evolution of Developmental Programs for the Midline Structures in Chordates: Insights From Gene Regulation in the Floor Plate and Hypochord Homologues of Embryos.

In vertebrate embryos, dorsal midline tissues, including the notochord, the prechordal plate, and the floor plate, play important roles in patterning of the central nervous system, somites, and endodermal tissues by producing extracellular signaling molecules, such as Sonic hedgehog (Shh). In , , one of the two genes, is expressed in the floor plate of the embryonic neural tube, while none of the genes are expressed in the notochord. We have identified a -regulatory region of that was sufficient to drive a reporter gene expression in the floor plate.