Involvement of the nerve growth factor-inducible large external glycoprotein (NILE) in neurite fasciculation in primary cultures of rat brain.

The nerve growth factor-inducible large external glycoprotein (NILE) has been found only on the surface of neuronal cells and Schwann cells. Since NILE seems to be concentrated on neurites, we have investigated its possible role in the development of neurites in primary cultures of rat brain. Cultures of embryonic day 14 (E14) whole brain and cultures of postnatal day 5 (P5) cerebellum were grown in the presence of Fab' fragments of antibody against NILE in an attempt to perturb the normal pattern of neurite development. For comparison, cultures were treated with two other reagents that recognize neuronal cell surface molecules: tetanus toxin, which binds to the GD1b and GT1 gangliosides, and Fab' fragments of antibody against neural cell adhesion molecule (N-CAM). Under the conditions used, none of the exogenous reagents affected neurite outgrowth, but specific effects on neurite fasciculation were observed. Anti-NILE inhibited fasciculation in cultures of E14 whole brain but had no effect on fasciculation in cultures of P5 cerebellum. Conversely, anti-N-CAM inhibited fasciculation in cultures of P5 cerebellum, which contain the adult form of N-CAM, but had little effect on fasciculation in cultures of E14 whole brain, which contain the embryonic form of N-CAM. Tetanus toxin had no effect on fasciculation in either culture system. Our results imply that NILE-mediated neurite-neurite interactions are stronger than N-CAM (embryonic)-mediated interactions in the E14 brain cultures, whereas N-CAM (adult)-mediated interactions are stronger than NILE-mediated interactions in the P5 cerebellar cultures.