Differentiation, extracellular matrix synthesis, and integrin assembly by Drosophila embryo cells cultured on vitronectin and laminin substrates

Abstract

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 αPS2βPS3 was essential for the initial spreading of myocytes on vitronectin: focal contacts rich in βPS3 integrins formed and were connected by actin‐ and myosin‐containing stress fibers. While αPS2βPS3 was unnecessary for myotube formation on laminin, it was required for the subsequent change to a sarcomeric cytoarchitecture. The differentiating primary cultures synthesized integrins and assembled them into detergent‐insoluble, cytoskeleton‐associated complexes. Collagen IV, laminin, glutactin, papilin, and other other extracellular matrix proteins were made primarily by hemocytes and were secreted into the medium. Further differentiation within the cultures was influenced by secreted components and by later addition of vitronectin or bovine serum. Comparison of the differentiation of various cell types on the two substrates showed that vitronectin provided a selective advantage for the differentiation of myocytes, with enrichment over epithelia, epidermal cells, and neurites. © 1994 Wiley‐Liss, Inc. Copyright © 1994 Wiley‐Liss, Inc.