Tracking oligodendrocytes during development and regeneration

Over the past decade, advances in strategies to tag cells have opened new a venues for examining the development of myelin-forming glial cells and for monitoring transplanted cells in animal models of myelin insufficiency. The strategies for labelling glial cells have encompassed a range of genetic m odifications as well as methods for directly attaching labels to cells. Gen etically modified oligodendrocytes have been engineered to express enzymati c (e.g., beta -galactosidase, alkaline phosphatase), naturally fluorescent (e.g., green fluorescent protein), and antibiotic resistance (e.g., neomyci n, zeomycin) reporters. Genes have been introduced in vivo and in vitro wit h viral or plasmid vectors to somatically label glial cells. To generate ge rm-line transmission of tagged oligodendrocytes, transgenic mice have been created both by direct injection into mouse fertilized eggs and. by "knock- in" of reporters targetted to myelin gene loci in embryonic stem cells. Eac h experimental approach has advantages and limitations that need to be cons idered for individual applications. The availability of tagged glial cells has expanded our basic understanding of how oligodendrocytes are specified from stem cells and should continue to fill in the gaps in our understandin g of how oligodendrocytes differentiate, myelinate, and maintain their myel in sheaths. Moreover, the ability to select oligodendrocytes by virtue of t heir acquired antibiotic resistance has provided an important new tool for isolating and purifying oligodendrocytes. Tagged glial cells have also been invaluable in evaluating cell transplant therapies in the nervous system. The tracking technologies that have driven these advances in glia cell biol ogy are continuing to evolve and present new opportunities for examining ol igodendrocytes in living systems. Published 2001 Wiley-Liss, Inc.dagger