Faithful activation of an extra‐bright red fluorescent protein in “knock‐in” Cre‐reporter mice ideally suited for lineage tracing studies

• Published in: European journal of immunology 2007-01, Vol.37 (1), p.43-53
• Main Authors: Luche, Hervé, Weber, Odile, Nageswara Rao, Tata, Blum, Carmen, Fehling, Hans Jörg
• Format: Article
• Language: English
• Subjects: Animals; Cell Line; Cell Lineage - genetics; Cre recombinase; Crosses, Genetic; Extracellular Matrix Proteins - genetics; Female; Gene Expression Regulation; Genes, Reporter; Integrases - genetics; Lineage tracing; Luminescent Proteins - biosynthesis; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Inbred DBA; Mice, Inbred Strains; Mice, Mutant Strains; Mice, Transgenic; Protein-Lysine 6-Oxidase - genetics; Red Fluorescent Protein; Reporter mouse; ROSA26 locus
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/eji.200636745

The considerable potential of Cre recombinase as a tool for in vivo fate‐mapping studies depends on the availability of reliable reporter mice. By targeting a tandem‐dimer red fluorescent protein (tdRFP) with advanced spectral and biological properties into the ubiquitously expressed ROSA26 locus of C57BL/6‐ES cells, we have generated a novel inbred Cre‐reporter mouse with several unique characteristics. We directly demonstrate the usefulness of our reporter strain in inter‐crosses with a “universal Cre‐deleter” strain and with mice expressing Cre recombinase in a T lineage‐specific manner. Cytofluorometric and histological analyses illustrate: (i) non‐toxicity and extraordinary brightness of the fluorescent reporter, allowing quantitative detection and purification of labeled cells with highest accuracy, (ii) reliable Cre‐mediated activation of tdRFP from an antisense orientation relative to ROSA26 transcription, effectively excluding “leaky” reporter expression, (iii) absence of gene expression variegation effects, (iv) quantitative detection of tdRFP‐expressing cells even in paraformaldehyde‐fixed tissue sections, and (v) full compatibility with GFP/YFP‐based fluorescent markers in multicolor experiments. Taken together, the data show that our C57BL/6‐inbred reporter mice are ideally suited for sophisticated lineage‐tracing experiments requiring sensitive and quantitative detection/purification of live Cre‐expressing cells and their progeny.