An L1-like molecule, the 8D9 antigen, is a potent substrate for neurite extension.

The 8D9 antigen, a cell surface protein isolated from chicken brain that is related to the L1 class of cell adhesion molecules, is shown to contain an activity that promotes the attachment of neurons and the outgrowth of neurites from chicken tecta and mouse cerebellum. When purified 8D9 antigen is attached to a nitrocellulose-coated substrate, neurons rapidly attach and extend unfasciculated neurites. Little or no attachment of astroglia, oligodendroglia, and fibroblast-like cells to the 8D9 antigen is observed. We propose that a function of the 8D9 antigen is that of a neurite extension-promoting substrate in axon fascicles and in regeneration of peripheral nerves.