CHANGING DISTRIBUTIONS OF EXTRACELLULAR-MATRIX COMPONENTS DURING EARLY WING MORPHOGENESIS IN DROSOPHILA

A new monoclonal antibody, specific to an epitope in the carboxyl term inus of the Drosophila collagen IV molecule (basement membrane collage n) was identified. The distributions of collagen IV, laminin, and an a dditional extracellular molecule, the 2G2 antigen (2G2-Ag), were follo wed immunocytochemically during early wing development. In late third instar larvae, collagen IV and laminin surround the entire wing disc, whereas the 2G2-Ag is limited to the region of the future wing pouch. For the first few hours following eversion of the disc, all three ECM components line the basal surfaces of all epithelial cells in the wing pouch, both those destined to line the wing veins and those destined to become tightly apposed in the large intervein regions. Collagen IV and laminin persist on these cells during the two initial rounds of ap position of dorsal and ventral wing surfaces; later, they become restr icted to the cells lining the veins. The 2G2-Ag disappears completely quite early in the pupal period. Collagen IV appears to be synthesized at least twice, once in the larva and a second time in the pupa; in b etween it is enzymatically cleaved and may be eliminated, probably by hemocytes. In an extreme allele of blistered the wing is ballooned to form a single internal space. Collagen IV and laminin line all basal w ing cell surfaces early in pupal development as they do in the wild ty pe. Later, however, they continue to line the entire cavity of the mut ant wing rather than assuming a restricted distribution. In a complete ly veinless wing (rhomboid(veinlet)vein), collagen IV and laminin are also present generally on basal surfaces at early times, but are compl etely absent between the tightly apposed wing layers later. The ECM di stributions both in wild type wings and in mutants suggest that the ma trix plays a role in the establishment of the wing venation pattern. O ne possibility, strengthened by recent findings regarding ECM receptor s in Drosophila, is their involvement in dorsal-ventral wing layer adh esion. Our findings also lead us to suggest that certain sets of featu res which distinguish vein from intervein cells may be linked during c ell differentiation and thus help to define these cell phenotypes. The features include cytoskeletal specializations and certain cell surfac e and ECM molecules. (C) 1995 Academic Press, Inc.