Comparative analysis of Schwann cell lines as model systems for myelin gene transcription studies

Primary and immortalized cultured Schwann cells are commonly utilized in analyses of myelin gene promoters, but few lines are well-characterized in terms of their endogenous expression of myelin genes. This is particularly significant in that cultured Schwann cells typically do not express myelin genes at levels comparable to those observed in vivo. In this study, the steady-state levels of mRNA and protein for five Schwann cell markers (PMP22, P0, MBP, MAG, and LNGF-R) were assessed in primary Schwann cells and six representative Schwann cell lines (RT4-D6P2T, JS-1, RSC96, R3, S16, and S16Y). RT4-D6P2T and S16 cells were the most similar to myelinating Schwann cells based on their comparatively high expression of PMP22 and P0 mRNA. Both RT4-D6P2T and S16 also expressed P0 protein. In addition, the previously reported P1-A positive regulatory region from the myelination-specific PMP22 promoter demonstrated significant activity in both these cell lines. However, nuclear proteins that interacted with P1-A were different in extracts prepared from RT4-D6P2T and S16 cells. Primary Schwann cells expressed myelin proteins at levels that were equal or less than those observed with the RT4-D6P2T and S16 lines, indicating that primary Schwann cells are not necessarily better than immortalized Schwann cells as model systems for the study of myelin gene regulation. The data presented here demonstrate that cultured Schwann cells used to study myelin gene promoters have to be carefully selected on the basis of the endogenous level of expression of the myelin gene under study.