The AN2 protein is a novel marker for the Schwann cell lineage expressed by immature and nonmyelinating Schwann cells

The expression of the 330 kDa AN2 glycoprotein was studied in the rodent pe ripheral nervous system. AN2 is expressed by immature Schwann cells in vitr o and in vivo and downregulated as the cells upregulate myelin genes. A sub population of nonmyelinating Schwann cells in the adult sciatic nerve retai ns expression of AN2. In rat sciatic nerve crushes, where Schwann cell numb ers increase after initial axonal loss and markers of immature Schwann cell s show an upregulation, no increased expression of AN2 was observed. In con trast, AN2 expression was upregulated in nerves from peripheral myelin prot ein-22-transgenic rats, where immature Schwann cells expand without axonal loss. Furthermore, coculture with neurons upregulated AN2 expression on Sch wann cells in vitro. Polyclonal antibodies against AN2 inhibited the migrat ion of an immortalized Schwann cell clone in an in vitro migration assay, a nd the purified AN2 protein was shown to be neither inhibitory nor permissi ve for outgrowing dorsal root ganglion neurites. AN2 is thus a novel marker for the Schwann cell lineage. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of purified AN2 from early postna tal mouse brain demonstrated that AN2 is the murine homolog of the rat NG2 proteoglycan.