DIFFERENTIATION, EXTRACELLULAR-MATRIX SYNTHESIS, AND INTEGRIN ASSEMBLY BY DROSOPHILA EMBRYO CELLS CULTURED ON VITRONECTIN AND LAMININ SUBSTRATES

Two contrasting substrates, Drosophila laminin and human vitronectin, caused determined primary Drosophila embryo cells to follow alternate intermediate differentiation steps without affecting the final outcome of differentiation. Integrin alpha(PS2)beta(PS3) was essential for th e initial spreading of myocytes on vitronectin: focal contacts rich in beta(PS3) integrins formed and were connected by actin- and myosin-co ntaining stress fibers. While alpha(PS2)beta(PS3) was unnecessary for myotube formation on laminin, it was required for the subsequent chang e to a sarcomeric cytoarchitecture. The differentiating primary cultur es synthesized integrins and assembled them into detergent-insoluble, cytoskeleton-associated complexes. Collagen IV, laminin, glutactin, pa pilin, and other extracellular matrix proteins were made primarily by hemocytes and were secreted into the medium. Further differentiation w ithin the cultures was influenced by secreted components and by later addition of vitronectin or bovine serum. Comparison of the differentia tion of various cell types on the two substrates showed that vitronect in provided a selective advantage for the differentiation of myocytes, with enrichment over epithelia, epidermal cells, and neurites. (C) 19 94 Wiley-Liss, Inc.