Schwann cells ensheathing) axons in unmyelinated fibers outnumber those that ensheath and myelinate axons, and therefore constitute an important category of peripheral glia. In comparison with myelin-forming cells, relatively little is known about the specific molecular characteristics of these cells. It is clearly important to establish to what extent these Schwann cells possess a distinctive molecular phenotype and the extent to which this phenotype is controlled by axons or other environmental influences.

In this paper we will focus on three different aspects of the biology of non-myelinforming Schwann cells. In the first part we will show that non-myelin-forming Schwann cells express several proteins that are also expressed by astrocytes and enteric glial cells. These molecules are not expressed in situ by myelin-forming cells, although two of them are expressed by myelin-forming cells when they are removed from axonal contact and placed into dissociated cell culture. Our results suggest that the phenotype of non-myelin-forming Schwann cells, astrocytes, and enteric glia in situ is similar, possibly reflecting common functions shared by non-myelin-forming cells of the central and peripheral nervous system.