Embryonic stem cells and transgenic mice ubiquitously expressing a tau-tagged green fluorescent protein.

We have generated embryonic stem (ES) cells and transgenic mice carrying a tau-tagged green fluorescent protein (GFP) transgene under the control of a powerful promoter active in all cell types including those of the central nervous system. GFP requires no substrate and can be detected in fixed or living cells so is an attractive genetic marker. Tau-tagged GFP labels subcellular structures, including axons and the mitotic machinery, by binding the GFP to microtubules. This allows cell morphology to be visualized in exquisite detail. We test the application of cells derived from these mice in several types of cell-mixing experiments and demonstrate that the morphology of tau-GFP-expressing cells can be readily visualized after they have integrated into unlabeled host cells or tissues. We anticipate that these ES cells and transgenic mice will prove a novel and powerful tool for a wide variety of applications including the development of neural transplantation technologies in animal models and fundamental research into axon pathfinding mechanisms. A major advantage of the tau-GFP label is that it can be detected in living cells and labeled cells and their processes can be identified and subjected to a variety of manipulations such as electrophysiological cell recording.