Syndecan‐3 and perlecan are differentially expressed by progenitors and mature oligodendrocytes and accumulate in the extracellular matrix

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Abstract
Oligodendrocyte progenitors originate in the subventricular zone, proliferate, migrate to their final destinations, differentiate, and interact with axons to produce multilamellar myelin sheaths. These processes are regulated by a variety of environmental signals, including growth factors, the extracellular matrix, and adhesion molecules. Heparan sulfate proteoglycans are premier candidates as participants in this regulation by virtue of their structural diversity and their capacity to function as coreceptors for both growth factors and extracellular matrix molecules. Consistently with this, we have previously shown that oligodendrocyte progenitors are unable to proliferate in response to fibroblast growth factor‐2 (FGF‐2) in the absence of sulfated heparan sulfate proteoglycan. Here we show that members of three families of heparan sulfate proteoglycans, syndecan, perlecan, and glypican, are developmentally and posttranscriptionally regulated during oligodendrocyte‐lineage progression: Syndecan‐3 is synthesized by oligodendrocyte progenitors (but not terminally differentiated oligodendrocytes) and is up‐regulated by FGF‐2; perlecan synthesis increases as oligodendrocytes undergo terminal differentiation; glypican‐1 is expressed by both progenitors and differentiated oligodendrocytes. Astrocytes express glypican‐1 and perlecan but not syndecan‐3. All three of these heparan sulfate proteoglycans are shed from the cell surface and bind to specific substrates. The developmentally regulated expression of these heparan sulfate proteoglycans is indicative of their participation in events involving growth factor receptors and the extracellular matrix that may regulate oligodendrocyte progenitor proliferation, migration, and adhesion phenomena.