JAGGED - A MAMMALIAN LIGAND THAT ACTIVATES NOTCH1

Here we report the isolation of a rat cDNA clone, Jagged, which we sho w encodes a ligand for vertebrate Notch. Our conclusion is based on th ree observations. First, sequence analysis reveals substantial homolog y between Jagged and invertebrate ligands for the LIN-12/Notch protein s. Second, in situ hybridization of rat embryos identifies both distin ct and overlapping patterns of gene expression for Jagged with those f or Notch1, Notch2, and Notch3. Finally, the biological activity of Jag ged was tested using a cell culture assay in which Jagged activates ra t Notch1 expressed in myoblasts and prevents muscle cell differentiati on. Our data support the hypothesis that Notch-ligand interactions fun ction in maintaining mammalian cells in an undifferentiated state.