Increased expression of integrin and receptor tyrosine kinase genes duringautograft fusion in the sponge Geodia cydonium

Recently cDNAs coding for cell surface molecules have been isolated from sp onges. The molecules for alpha-integrin, galectin, and receptor tyrosine ki nase (RTK), obtained from the marine sponge, Geodia cydonium?, have been de scribed earlier, In the present study also the cDNA for one putative beta-i ntegrin has been identified from G, cydonium. The deduced aa sequence compr ises the characteristic signatures, found in other metazoan beta-integrin m olecules; the estimated size is 95,215 Da, To obtain first insights into th e molecular events which proceed during autograft fusion, the expressions o f these genes were determined on transcriptional and translational level. T he cDNAs as well as antibodies raised against the recombinant sponge protei ns alpha-integrin, RTK and galectin were used and Northern blot experiments and immunocytochemical analyses have been performed. The results show that transcription of the two subunits of an integrin receptor as well as of th e RTK are strongly upregulated after grafting; levels of > 10-fold have bee n determined in the fusion zone of the grafts after a 10 days incubation. I mmunofluorescence studies of sections through the fusion zone support these data, In contrast the transcription of the gene encoding galectin is drast ically downregulated after grafting, In a parallel series of experiments th e level of the heat-shock protein-70 was determined and it was found that i t remained unchanged after grafting, We conclude that integrin subunits and the RTK molecule are involved in self-self recognition of sponge.