Fibronectin is apparently not involved in species‐specific reaggregation of cells from the marine sponge geodia cydonium

Abstract

Experiments were carried out to test the hypothesis that fibronectin is involved in reaggregation of dissociated sponge cells. Cells from the siliceous sponge Geodia cydonium were extracted with urea to solubilize fibronectin from cells of higher multicellular organisms. The crude extract was further fractionated by DNA, heparin, and collagen affinity chromatography; they were termed Geodia fibronectin like fractions. The fibronectin like fractions contained a series of proteins with molecular weights different from that of the genuine fibronectin. The Geodia fibronectin like fractions did not react with antiserum, produced against human fibronectin, under formation of a precipitin line. Using this antiserum the sponge cells could not be specifically labeled with FITC-anti-IgG antiserum. Radioimmunoprecipitation experiments revealed that the Geodia fractions contain--if at all--0.1% fibronectin or fibronectin like protein at the most. In the crucial experiments it was shown that the Geodia fibronectinlike fractions, human fibronectin, and antifibronectin antiserum exerted no influence on adhesion of Geodia cells either in the absence or in the presence of the soluble aggregation factor. Based on these findings, we conclude that fibronectin is apparently not present on Geodia cells and does not play a role in aggregation of this biological system.

The Cell Biology of Sponges

“…At about 4 h of incubation an AF-dependent increase in DNA synthesis occurs which can be blocked by bleomycin, actinomycin D, and puromycin (Muller et ai., 1976). In this system AF is also reported to increase O2 uptake and cause changes in cyclic nucleotides (see Muller, 1982). It is to be emphasized that these reported events occur well after the initial cell adhesion stage and deal with older aggregates (Muller, 1982).…”

“…In this system AF is also reported to increase O2 uptake and cause changes in cyclic nucleotides (see Muller, 1982). It is to be emphasized that these reported events occur well after the initial cell adhesion stage and deal with older aggregates (Muller, 1982). Further, the absence of gyratory shaking and the preparative employment of EDT A and trypsin in these experiments make it difficult to compare the results with those from experiments using the more usual protocol (Humphreys, 1963;Moscona, 1963;Kuhns et ai., 1974;Burger et ai., 1975).…”

“…The situation with factors that are inhibitory for cell aggregation is complicated by the finding that there are also factors that promote cell aggregation (Evans and Curtis, 1979). Grafts of Geodia rovinjensis are rejected by Geodia cydonium causing necrosis in the latter (Muller, 1982). A factor (glycoprotein) is produced by G. rovinjensis grafts which when injected into G. cydonium causes necrosis.…”

“…A factor (glycoprotein) is produced by G. rovinjensis grafts which when injected into G. cydonium causes necrosis. This factor is also an inhibitor of cell aggregation, and Muller (1982) considers that it as well as other active components that are involved in in vitro cell aggregation are also the active substances in graft rejection and graft acceptance. Given the present state of knowledge, the excitement of these correlations has to be modulated with some caution since we do not even know the precise cell activities involved in graft rejection (necrosis) or for that matter in isograft acceptance.…”

“…Preparations of Helix glusulase can destroy the effectiveness of Microciona AF and this is due at least partially to the presence of glucuronidase activity indicating a critical role for glucuronic acid in the activity of AF (Turner et aI., 1974); periodate treatment also inactivates the factor , although it does not substantially effect AF"';cell binding (Jumblatt et ai., 1980). In distinction, Geodia AF is not inactivated by beta glucuronidase (Muller, 1982). The use of commercially available lectins has aided in establishing a role for specific sugars in sponge cell adhesions.…”