Dissociated cells of the calcareous sponge Clathrina: a model for investigating cell adhesion and cell motility in vitro

The study of cell-cell and cell-substratum adhesion in vitro is useful for understanding cell behavior in a three-dimensional pattern. We have used di ssociated cells (choanocytes represent the main fraction) from the calcareo us sponge Clathrina, namely C. cerebrum and C. clathrus, to illustrate our present understanding on three main aspects of cell-cell and cell-substratu m adhesion in vitro: (1) cytoskeletal protrusions; (2) cell behaviours on o rganic substrata; and (3) paths of locomotory sponge cell. Cell locomotion occurs by the extensions of scleropodial and lamellipodial protrusions, by way of actin polymerization. The extent to which cells produce these cytopl asmic processes varies according to the substratum (e.g., collagen, fibrone ctin, laminin, polylysine). It was found that more cell extensions were pro duced on collagen substrata, and this led to greater cell movement. Advanci ng choanocytes are not polarized. Their paths are particularly complicated, showing linear segments, which produce a more efficent cellular translocat ion, and winding tracts with frequent turns or loops. Small amoeboid cells describe more linear paths with a wide range of speed variation than larger cells. The presence of cell-derived substratum reduces the progressive dis persion of cells and allows cells to encounter one another in such a way th at the initial random walking later turns into non-random displacement. Eve n though cAMP-treated cells exhibit different aggregative tactics, cAMP 10( -8) M remarkably enhances cell encounters and supports the existing informa tion that this cyclic nucleotide represents a signal that affects cell morp hology and locomotion. The bulk of data on sponge cell-cell and cell-substr atum adhesion has been evaluated by mentioning the significant advances and references concerning studies of other cell systems. Microsc. Res. Tech. 4 4:279-292, 1999. (C) 1999 Wiley-Liss, Inc.