Expressing antisense P0 RNA in Schwann cells perturbs myelination

Primary Schwann cells were infected in vitro with a recombinant retrovirus expressing a dominant selectable marker, neomycin phosphotransferase (conferring resistance to the drug G418), and antisense P0 RNA under the control of the human beta-actin promoter. A proportion of the G418-resistant cells failed to form myelin when cocultured with dorsal root ganglion neurons under conditions that promote Schwann cell differentiation. These cells expressed high levels of P0 antisense RNA. Among the impaired cells, the majority had segregated and ensheathed individual axon but had not differentiated further. They did not express P0 but did express myelin- associated glycoprotein and galactocerebroside. A minority of partially inhibited Schwann cells were also observed that elaborated thin myelin sheaths containing variable numbers of compacted and noncompacted lamellae. These data indicate that restricting the level of P0 expression inhibits spiralling of the Schwann cell membrane and subsequent compaction.