A histological survey of green fluorescent protein expression in 'green' mice: implications for stem cell research.
OBJECTIVE
The transgenic enhanced green fluorescent protein (EGFP) expressing 'green' mouse (C57BL/6-TgN(ACTbEGFP)1Osb) is a widely used tool in stem cell research, where the ubiquitous nature of EGFP expression is critical to track the fate of single or small groups of transplanted haematopoietic stem cells (HSC). Our aim was to investigate this assumed ubiquitous expression by performing a detailed histological survey of EGFP expression in these mice.


METHODS
Fluorescent microscopy of frozen tissue sections was used to perform a detailed histological survey of the pattern of EGFP expression in these mice. Flow cytometry was also used to determine the expression pattern in blood and bone marrow.


RESULTS
Three patterns of EGFP expression were noted. In most tissues there was an apparently stochastic variegation of the transgene, with individual cell types demonstrating highly variable rates of EGFP expression. Certain specific cell types such as pancreatic ductal epithelium, cerebral cortical neurones and glial cells and glomerular mesangial cells consistently lacked EGFP expression, while others, including pancreatic islet cells, expressed EGFP only at extremely low levels, barely distinguishable from background. Lastly, in the colon and stomach the pattern of EGFP expression was suggestive of clonal inactivation. Only cardiac and skeletal muscle showed near ubiquitous expression.


CONCLUSIONS
These findings raise questions regarding the 'ubiquitous' expression of EGFP in these transgenic mice and suggest caution in relying overly on EGFP alone as an infallible marker of donor cell origin.
Biankin
Sandra A
SA
Epithelial Stem Cell Working Group, Department of Surgery, Sidney Kimmel Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, USA. s.biankin@garvan.org.au
Collector
Michael I
MI
Biankin
Andrew V
AV
Brown
Lindsey J
LJ
Kleeberger
Wolfram
W
Devereux
Wendy L
WL
Zahnow
Cynthia A
CA
Baylin
Stephen B
SB
Watkins
D Neil
DN
Sharkis
Saul J
SJ
Leach
Steven D
SD
D000818:Animals; D035843:Biomedical Research / Q000379:methods*; D019070:Cell Lineage; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D049452:Green Fluorescent Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D023421:Models, Animal; D013234:Stem Cells
D049452:Green Fluorescent Proteins