At the Sign of the Star by Katherine Sturtevant

Receptor tyrosine kinases (RTKs) mediate diverse processes including cell fate determination during development and control of cell proliferation in response to growth factors. These data indicate that rho and S act in concert, but independently of spi, to promote vein development through the EGFR/MAPK signaling pathway. In contrast, spi does not play an essential role in the wing. Furthermore, mis-expression of rho and S in wild-type and mutant backgrounds reveals that these genes function in a synergistic and co-dependent manner. We show that rho and S function in a common aspect of vein development since loss-of-function clones of rho or S result in nearly identical non-autonomous loss-of-vein phenotypes. Epistasis studies using a dominant negative version of Egfr and a ligand-independent activated form of Egfr suggest that rho acts upstream of the receptor. Consistent with this observation, rho activity is necessary and sufficient to activate MAPK in vein primordium during late larval and early pupal stages. In this study, we show that rho-mediated hyperactivation of the EGFR/MAPK pathway is required for vein formation throughout late larval and early pupal development. Among these genes, Egfr encodes the Drosophila EGF-Receptor, spitz ( spi) and vein ( vn) encode EGF-related ligands, and rhomboid ( rho) and Star ( S) encode membrane proteins. Genes of the ventrolateral group in Drosophila are dedicated to developmental regulation of Egfr signaling in multiple processes including wing vein development.

At the Sign of the Star by Katherine Sturtevant