Bovine CNS Myelin Contains Neurite Growth-Inhibitory Activity Associated with Chondroitin Sulfate Proteoglycans

Abstract

The absence of fiber regrowth in the injured mammalian CNS is influenced by several different factors and mechanisms. Besides the nonconducive properties of the glial scar tissue that forms around the lesion site, individual molecules present in CNS myelin and expressed by oligodendrocytes, such as NI-35/NI-250, bNI-220, and myelin-associated glycoprotein (MAG), have been isolated and shown to inhibit axonal growth. Here, we report an additional neurite growth-inhibitory activity purified from bovine spinal cord myelin that is not related to bNI-220 or MAG. This activity can be ascribed to the presence of two chondroitin sulfate proteoglycans (CSPGs), brevican and the brain-specific versican V2 splice variant. Neurite outgrowth of neonatal cerebellar granule cells and of dorsal root ganglion neurons in vitro was strongly inhibited by this myelin fraction enriched in CSPGs. Immunohistochemical staining revealed that brevican and versican V2 are present on the surfaces of differentiated oligodendrocytes. We provide evidence that treatment of oligodendrocytes with the proteoglycan synthesis inhibitors beta-xylosides can strongly influence the growth permissiveness of oligodendrocytes. beta-Xylosides abolished cell surface presentation of brevican and versican V2 and reversed growth cone collapse in encounters with oligodendrocytes as demonstrated by time-lapse video microscopy. Instead, growth cones were able to grow along or even into the processes of oligodendrocytes. Our results strongly suggest that brevican and versican V2 are additional components of CNS myelin that contribute to its nonpermissive substrate properties for axonal growth. Expression of these CSPGs on oligodendrocytes may indicate that they participate in the restriction of structural plasticity and regeneration in the adult CNS.

Brevican isoforms associate with neural membranes

“…The myelin fraction contains low-density lipids that are derived from axonal myelin sheaths. The presence of brevican in this fraction has already been reported (Seidenbecher et al 1998;Niederöst et al 1999) and it was suggested to contribute to the nonpermissive properties of CNS myelin (Niederöst et al 1999). The light membrane fraction is a less well defined membrane subpopulation, which contains a mixture of endoplasmic reticulum, Golgi and plasma membranes as estimated by electron microscopy (Cohen et al 1977;Hu et al 1998).…”

MICAL flavoprotein monooxygenases: Expression during neural development and following spinal cord injuries in the rat

“…P0 -P1 rat DRG explants were grown on myelin-coated coverslips in the absence or presence of 10 or 25 AM EGCG. Myelin was prepared from adult rat spinal cords as described (Niederost et al, 1999). For myelin substrate assays, wells of a four-well tissue culture dish were precoated with 20 Ag/ ml poly-l-lysine for 2 h at RT.…”

Truncated Soluble Nogo Receptor Binds Nogo-66 and Blocks Inhibition of Axon Growth by Myelin

“…Multiple inhibitors have been identified in myelin (McKerracher et al, 1994;Mukhopadhyay et al, 1994;Niederost et al, 1999), and one of the most potent inhibitors may be Nogo (Caroni and Schwab, 1988a;Chen et al, 2000;GrandPre et al, 2000;Prinjha et al, 2000). This contention is supported by experiments showing that treatment with the inhibitor neutralization (IN-1) antibody, which recognizes Nogo-A, enhanced neurite outgrowth and functional recovery after CNS spinal cord injuries in rats (Caroni and Schwab, 1988b;Schnell and Schwab, 1990).…”