MOLECULAR, PHENOTYPIC, AND EXPRESSION ANALYSIS OF VEIN, A GENE REQUIRED FOR GROWTH OF THE DROSOPHILA WING DISC

vein(1) (vn(1)) mutants lack portions of longitudinal wing vein 4 and the anterior crossvein. Stronger alleles, originally called defective dorsal discs, show vn is also required for the growth of the wing and haltere discs, as mutants for these alleles have tiny dorsal discs. vn functions nonautonomously and encodes a secreted EGF-like protein. He re we characterize the role of vn in the imaginal wing disc by describ ing the expression pattern and correlating this pattern with vn mutant phenotypes and the requirement for vn. vn is expressed in wing discs in a complex and dynamic pattern. In larval wing discs vn is first exp ressed in the presumptive notum and later in the wing-pouch and hinge regions. There is a striking localization of vn transcripts to interve in regions which begins with a stripe of expression straddling the AP boundary in late larval discs and develops in all intervein regions af ter puparium formation. We isolated new vn mutations including nulls a nd hypomorphs. Hypomorphic vn alleles revealed region-specific require ments for vn within the wing disc. We mapped lesions caused by 10 vn m utations and defined a minimum size of 48 kb for the gene. The phenoty pe and expression analyses show vn has an early role in global prolife ration of the wing disc and specific roles in the development of the n otum, hinge, longitudinal vein 4, and all intervein regions. The role of vn in the EGF receptor signaling pathway is discussed. (C) 1996 Aca demic Press, Inc.