SONIC-HEDGEHOG, A MEMBER OF A FAMILY OF PUTATIVE SIGNALING MOLECULES,IS IMPLICATED IN THE REGULATION OF CNS POLARITY

We have identified three members of a mouse gene family related to the Drosophila segment polarity gene, hedgehog (hh). Like hh, they encode putative secreted proteins and are thus implicated in cell-cell inter actions. One of these, Sonic hh (Shh), is expressed in the notochord, the floor plate, and the zone of polarizing activity, signaling center s that are thought to mediate central nervous system (CNS) and limb po larity. Ectopic expression of Shh in the mouse CNS leads to the activa tion of floor plate-expressed genes. These results suggest that Shh ma y play a role in the normal inductive interactions that pattern the ve ntral CNS.