Cre reporter strains produced by targeted insertion of EYFP and ECFP into the ROSA26 locus.
BACKGROUND
Several Cre reporter strains of mice have been described, in which a lacZ gene is turned on in cells expressing Cre recombinase, as well as their daughter cells, following Cre-mediated excision of a loxP-flanked transcriptional "stop" sequence. These mice are useful for cell lineage tracing experiments as well as for monitoring the expression of Cre transgenes. The green fluorescent protein (GFP) and variants such as EYFP and ECFP offer an advantage over lacZ as a reporter, in that they can be easily visualized without recourse to the vital substrates required to visualize beta-gal in living tissue.


RESULTS
In view of the general utility of targeting the ubiquitously expressed ROSA26 locus, we constructed a generic ROSA26 targeting vector. We then generated two reporter lines of mice by inserting EYFP or ECFP cDNAs into the ROSA26 locus, preceded by a loxP-flanked stop sequence. These strains were tested by crossing them with transgenic strains expressing Cre in a ubiquitous (beta-actin-Cre) or a cell-specific (Isl1-Cre and En1-Cre) pattern. The resulting EYFP or ECFP expression patterns indicated that the reporter strains function as faithful monitors of Cre activity.


CONCLUSIONS
In contrast to existing lacZ reporter lines, where lacZ expression cannot easily be detected in living tissue, the EYFP and ECFP reporter strains are useful for monitoring the expression of Cre and tracing the lineage of these cells and their descendants in cultured embryos or organs. The non-overlapping emission spectra of EYFP and ECFP make them ideal for double labeling studies in living tissues.
Srinivas
S
S
Department of Genetics and Development, Columbia University, New York, USA. shankar@srinivas.org
Watanabe
T
T
Lin
C S
CS
William
C M
CM
Tanabe
Y
Y
Jessell
T M
TM
Costantini
F
F
D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002460:Cell Line; D004622:Embryo, Mammalian; D005260:Female; D018390:Gene Targeting / Q000379:methods*; D017930:Genes, Reporter / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics*; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D019426:Integrases / Q000235:genetics*; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D016254:Mutagenesis, Insertional; D011506:Proteins / Q000235:genetics*; D022661:RNA, Untranslated; D011995:Recombination, Genetic / Q000235:genetics; D013234:Stem Cells / Q000737:chemistry / Q000378:metabolism; D014162:Transfection; D014764:Viral Proteins / Q000235:genetics*
D001426:Bacterial Proteins; D005819:Genetic Markers; C110853:Gt(ROSA)26Sor non-coding RNA, mouse; D008164:Luminescent Proteins; D011506:Proteins; D022661:RNA, Untranslated; D014764:Viral Proteins; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; C045073:Cre recombinase; D019426:Integrases