Purified secretory glycoproteins of the bovine subcommissural organ influence neuronal differentiation in vitro

The subcommissural organ-spondin (SCO-spondin), a glycoprotein belonging to the thrombospondin family, is secreted by specialyzed cells located at the floor and roof plates during the ontogenetic development of the central ne rvous system, and by the subcommissural organ (SCO) in adulthood. The intra cellular secretion of the bovine SCO was purified by immunoaffinity chromat ography with monoclonal antibodies raised against the Reissner's fiber (RF) , a fibrous structure present at the ventricular cavities and that results from the polymerization of the SCO-spondin apically released by the SCO sec retory cells. The purified secretion was used as a SCO-spondin source and a ssayed on cultures of the rat neuroblastoma B104 cell line. High doses of S CO secretory glucoproteins inhibited the proliferation of cultured neurobla sts, while lower concentrations stimulated neurite outgrowth and cellular a ggregation.