Purification and analysis of in vivo-differentiated oligodendrocytes expressing the green fluorescent protein

A complete understanding of the molecular mechanisms involved in the format ion and repair of the central nervous system myelin sheath requires an unam biguous identification and isolation of in vivo-differentiated myelin-formi ng cells. In order to develop a novel tool for the analysis of in vive-diff erentiated oligodendrocytes, we generated transgenic mice expressing a red- shifted variant of the green fluorescent protein under the control of the p roteolipid protein promoter. We demonstrate here that green fluorescent pro tein-derived fluorescence in the central nervous system of 9-day- to 7-week -old mice is restricted to mature oligodendrocytes, as determined by its sp atiotemporal appearance and by both immunocytochemical and electrophysiolog ical criteria. Green fluorescent protein-positive oligodendrocytes could ea sily be visualized in live and fixed tissue. Furthermore, we show that this convenient and reliable identification now allows detailed physiological a nalyses of differentiated oligodendrocytes in situ. In addition, we develop ed a novel tissue culture system for in vive-differentiated oligodendrocyte s. Initial data using this system indicate that, for oligodendrocytes isola ted after differentiation in vivo, as yet unidentified factors secreted by astrocytes are necessary for survival and/or reappearance of a mature pheno type in culture. (C) 2000 Academic Press.