Despite the importance of myelinating Schwann cells in health and disease, little is known about the genetic mechanisms underlying their development. The POU domain transcription factor pou3f1 (Tst-1, SCIP, Oct-6) is required for the normal differentiation of myelinating Schwann cells, but its precise role requires identification of the genes that it regulates. Here we report the isolation of six genes whose expression is reduced in the absence of pou3f1. Only one of these genes, the fatty acid transport protein P2, was known previously to be expressed in Schwann cells. The LIM domain proteins cysteine-rich protein-1 (CRP1) and CRP2 are expressed in sciatic nerve and induced by forskolin in cultured Schwann cells, but only CRP2 requires pou3f1 for normal expression. pou3f1 appears to require the claw paw gene product for activation of at least some of its downstream effector genes. Expression of the novel Schwann cell genes after nerve injury suggests that they are myelin related. One of the genes, tramdorin1, encodes a novel amino acid transport protein that is localized to paranodes and incisures. Our results suggest that pou3f1 functions to activate gene expression in the differentiation of myelinating Schwann cells.

Many aspects of the response of Schwann cells to axonal cues can be induced in vitro by the adenylyl cyclase activator forskolin, yet the role of cAMP signaling in regulating Schwann cell differentiation remains unclear. To define better the relationship between cAMP signaling and Schwann cell differentiation, we used a modification of cDNA representational difference analysis (RDA) that permits the analysis of small amounts of mRNA and identified additional genes that are differentially expressed by forskolin-treated and untreated Schwann cells. The genes that we have identified, including MKP3, a regulator of ERK signaling, and the sphingosine-1-phosphate receptor edg3/lp(B3), may play important roles in mediating Schwann cell differentiation.