These embryonic stem cell lines each harbor a single tagged gene that expresses a fluorescent fusion protein that is controlled by the native regulation of the cell. The tag is placed using a novel system known as CD-tagging. This system places the DNA carrying the tag into an intron of a gene creating a new exon in the process. This exon then incorporates the tag into transcripts and ultimately into proteins. A schematic of the process is shown below:
The fluorescence in each cell of a particular clonal line will serve as a reporter for the expression level and subcellular localization of the tagged protein in that cell line. Since these cells are embryonic stem cells they can be manipulated in culture into specific tissue-types such as cardiomyocytes, to create a powerful new system for biomarker discovery and drug-screening relevant to important diseases such as cardiovascular disease. Further, these mES cells can also be used for the generation of transgenic mice as and when desired, to extend such studies to live animals.