Abstract
BackgroundNon-invasive autofluorescent reporters have revolutionized lineage labeling in an array of different organisms. In recent years green fluorescent protein (GFP) from the bioluminescent jellyfish Aequoria Victoria has gained popularity in mouse transgenic and gene targeting regimes [1]. It offers several advantages over conventional gene-based reporters, such as lacZ and alkaline phosphatase, in that its visualization does not require a chromogenic substrate and can be realized in vivo. We have previously demonstrated the utility and developmental neutrality of enhanced green fluorescent protein (EGFP) in embryonic stem (ES) cells and mice [2].ResultsIn this study we have used embryonic stem (ES) cell-mediated transgenesis to test the enhanced cyan fluorescent protein (ECFP) and enhanced yellow fluorescent protein (EYFP), two mutant and spectrally distinct color variants of wild type (wt) GFP. We have also tested DsRed1, the novel red fluorescent protein reporter recently cloned from the Discostoma coral by virtue of its homology to GFP. To this end, we have established lines of ES cells together with viable and fertile mice having widespread expression of either the ECFP or EYFP GFP-variant reporters. However, we were unable to generate equivalent DsRed1 lines, suggesting that DsRed1 is not developmentally neutral or that transgene expression cannot be sustained constitutively. Balanced (diploid <-> diploid) and polarized (tetraploid <-> diploid) chimeras comprising combinations of the ECFP and EYFP ES cells and/or embryos, demonstrate that populations of cells expressing each individual reporter can be distinguished within a single animal.ConclusionsGFP variant reporters are unique in allowing non-invasive multi-spectral visualization in live samples. The ECFP and EYFP-expressing transgenic ES cells and mice that we have generated provide sources of cells and tissues for combinatorial, double-tagged recombination experiments, chimeras or transplantations.
Highlights
Non-invasive autofluorescent reporters have revolutionized lineage labeling in an array of different organisms
It can be envisaged that two different fluorescent protein (FP) colors could be used in the construction of chimeras so as to tag both mutant and wild type lineages. From these observations we conclude that the blue-shifted enhanced cyan fluorescent protein (ECFP), and the red-shifted enhanced yellow fluorescent protein (EYFP) variants of wild type GFP (wtGFP) are both amenable to use in mice
Since we have established lines of viable and fertile mice having widespread FP expression we have demonstrated that ECFP and EYFP represent developmentally neutral reporters
Summary
Non-invasive autofluorescent reporters have revolutionized lineage labeling in an array of different organisms. In recent years green fluorescent protein (GFP) from the bioluminescent jellyfish Aequoria Victoria has gained popularity in mouse transgenic and gene targeting regimes [1]. It offers several advantages over conventional gene-based reporters, such as lacZ and alkaline phosphatase, in that its visualization does not require a chromogenic substrate and can be realized in vivo. The ease of manipulating its genome has helped establish the mouse as the premier model organism for mammalian genetic studies Both directed and random mutagenesis approaches, including the technologies of transgenesis and gene targeting in ES cells, have become common-. The prototype fluorescent protein reporter is green fluorescent protein (GFP, reviewed in [3]), which is derived from the bioluminescent jellyfish Aequorea Victoria [1]
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