ABSTRACT
The expression of the primary mesenchyme cell (PMC) surface specific antigen, and its role in the ingression and migration of PMCs and in the gastrulation were examined in the sea urchin, Clypeaster japonicus. The antigen bound a monoclonal antibody (MAb) B2C2, which has been raised against a PMC surface specific glycoprotein, msp 130, of the sea urchin, Strongylocentrotus purpuratus (Leaf, et al, 1987). The epitope recognized by the MAb was detected immunohistochemically exclusively on the PMCs only after the completion of their ingression in mesenchyme blastulae. Its expression was prevented in blastulae that were treated either with monensin or tunicamysin, and in those raised in sulfate-deficient sea water. These treatments also caused interruption of PMC migration. However, the introduction of either intact IgG or of its F(ab’)2 fragments into the blastocoel interrupted neither PMC migration nor gastrulation. Fibronectin-promoted PMC migration in vitro was also not interfered by B2C2 MAb. In conclusion, it was very unlikely that the B2C2 epitope is involved in either ingression, migration of PMCs or gastrulation.
