Positive selectable markers for use with mammalian cells in culture.

As more complicated gene expression studies are necessary, the need for multiple positive selection schemes becomes critical. Numerous selectable markers have been described over the last 25 years. A hallmark of the most generally useful markers is easy selection in a wide number of cell types. This paper briefly reviews the spectrum of available selectable markers and describes some of the applications that have been found for these genes, particularly with respect to retrovirus-mediated gene transfer.