Identification of new signaling components in the Drosophila genome sequence

The availability of the complete sequence of the Drosophila genome and the assignment of putative reading frames, provides an opportunity to search for new members in families of proteins generating signaling cascades. The six major pathways that dictate patterning were examined: receptor tyrosine kinases, transforming growth factor beta (TGFβ), Wnt, Toll, Hedgehog and Notch. Several new components were identified for the first four pathways, including ligands, receptors, cytoplasmic components and transcription factors. Most notable is the identification of a vascular endothelial growth factor (VEGF) receptor tyrosine kinase, two insulin/insulin growth factor I (IGF I) receptors without cytoplasmic protein kinase domains, and a family of proteins similar to Rhomboid (a protein involved in cleavage of TGFα-like ligands). A new TGFβ family ligand, two new Wnts and a Frizzled receptor were also identified. Finally, for the Toll pathway, two new potential Spatzle-like ligands and two new receptors were identified.