MAG-DEFICIENT SCHWANN-CELLS MYELINATE DORSAL-ROOT GANGLION NEURONS INCULTURE

The myelin-associated glycoprotein (MAG) has been postulated to play a crucial role during myelin formation. Evidence supporting this hypoth esis was provided by infecting rat Schwann cells with a retrovirus exp ressing MAG antisense RNA; these Schwann cells showed reduced levels o f MAG expression and failed to myelinate DRG neurons in vitro. However , when MAG expression was disrupted by generating MAG-deficient mice, normal myelin sheaths were formed in peripheral nerves in vivo. In the present study we investigated whether myelination is compromised in M AG-deficient Schwann cells in vitro, i.e., under similar conditions wh ere Schwann cells expressing MAG antisense RNA failed to myelinate. We show that MAC-deficient Schwann cells do myelinate DRG neurons in vit ro and express the myelin-specific glycolipid galactocerebroside (Gal- C) and the myelin proteins PO and MBP. Furthermore, myelin sheaths app ear morphologically normal with both compacted and uncompacted aspects when investigated by electron microscopy. Quantitative analysis revea led that the number of myelin sheaths was similar in cultures from MAG -deficient and wild-type mice. These findings support the view that MA G is not essential for myelin formation in the PNS. (C) 1998 Wiley-Lis s, Inc.