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

Abstract

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.

Extracellular Signal-regulated Kinase Activation Is Required for Serine 727 Phosphorylation of STAT3 in Schwann Cells in vitro and in vivo

“…A forceful activation of ERK led to the downregulation of markers of myelinating SCs, including as P0 and periaxin. ERK activation in the injured nerves in vivo further supports the notion that ERK signaling plays an important role in the phenotype changes occurring in myelinating SCs after peripheral nerve injury (Sheu et al, 2000;Harrisingh et al, 2004).…”

“…Although a great many factors are capable of inducing the phenotype changes of SCs in vitro, the intracellular signaling associated with SC dedifferentiation has yet to be thoroughly elucidated. It was reported recently that the Ras/extracellular signal-regulated kinase (ERK) pathway might drive the dedifferentiation of SCs in vitro (Harrisingh et al, 2004). A forceful activation of ERK led to the downregulation of markers of myelinating SCs, including as P0 and periaxin.…”

“…For example, neuregulins (NRG) may activate ERK for demyelination (Harrisingh et al, 2004). We recently reported that IL-6 activated ERK in SC-derived RT4 cells and primary SCs (Lee et al, 2009), even though the role of IL-6-induced ERK activation currently remains unknown.…”

“…We recently reported that IL-6 activated ERK in SC-derived RT4 cells and primary SCs (Lee et al, 2009), even though the role of IL-6-induced ERK activation currently remains unknown. In this study, we placed our focus on the possible role of the Ras/ERK pathway in STAT3 phosphorylation in primary SCs and RT4 cells (Hai et al, 2002), because it has already been established that the Ras/ERK pathway is either positively or negatively involved in STAT3 activation. We determined that ERK is an upstream kinase for the serine 727 phosphorylation of STAT3 in SCs in vitro and in vivo.…”

SOX10 regulates an alternative promoter at the Charcot-Marie-Tooth disease locusMTMR2

“…PMP22, MPZ, and SOX10) (22)(23)(24). Briefly, we cloned each genomic segment upstream of a minimal promoter directing the expression of a firefly luciferase reporter gene (25).…”