Functional characterization of toposomes from sea urchin blastula embryos by a morphogenetic cell aggregation assay.

This paper documents the evidence that the large oligomeric glycoprotein complexes of unknown function first isolated as 22S particles from sea urchin embryos are the sole agents responsible for the adhesive integrity of sea urchin blastula embryos. The conclusion rests on the demonstration that polyclonal IgG (as serum or monovalent Fab) against whole membranes or butanol-solubilized components of membranes, as well as against the purified particle itself, completely blocks reaggregation of dissociated blastula cells and that this inhibition is reversed by neutralization of the inhibitory antibodies with purified 22S antigen. An essential aspect of the evidence is the combination of quantitative endpoint titrations in microtiter wells with the qualitative parameters of morphogenesis.

Characterization of toposomes from sea urchin blastula cells: a cell organelle mediating cell adhesion and expressing positional information.

Cell adhesion in the sea urchin blastula is mediated by a 22S genus-specific glycoprotein complex consisting initially of six 160-kDa subunits that are processed proteolytically as development proceeds. Noncytolytic removal of the 22S particle from the surface with either 2.5% butanol or trypsin renders dissociated cells reaggregation incompetent, and addition restores reaggregation and development.