Non-invasive in vivo optical imaging of the lacZ and luc gene expression in mice.
The bacterial lacZ gene encoding for beta-galactosidase (beta-gal) is a common reporter gene used in transgenic mice. Nonetheless, the absence of fluorigenic substrates usable in live animals greatly hampered the non-invasive follow-up of this reporter gene expression. We used far-red fluorescence for imaging beta-Gal expression in live cells in vitro or in vivo. The 9H-(1,3-dichloro-9,9-dimethylacridin- 2-one-7-yl) beta-D-galactopyranoside substrate was used to monitor beta-Gal expression as a reporter of tumor growth, or of the physiological levels of an endogenous gene or of gene transfer in lung. A quantitative evaluation of this method as well as a comparison of its sensitivity with Firefly Luciferase-based bioluminescence was also performed. In vivo measurements showed that 10(3) beta-Gal tumor cells located under the skin were detectable. In deeper organs like lung, as little as 5 ng of beta-Gal or Luciferase enzymes per mg of proteins were measured, confirming that both techniques reached similar sensibilities. Nonetheless, quantitative comparison of beta-Gal levels measured with far-red imaging or with a standardized enzymatic evaluation after killing revealed that the 2D-fluorescent reflectance imaging method is submitted to a color-dependent disparity of the organs and cannot supply quantitative measurements but that a simple correction can be applied.
Josserand
V
V
INSERM U823, Institut Albert Bonniot, La Tronche Cedex, France.
Texier-Nogues
I
I
Huber
P
P
Favrot
M-C
MC
Coll
J-L
JL
D000818:Animals; D015870:Gene Expression; D017930:Genes, Reporter; D005819:Genetic Markers; D015316:Genetic Therapy / Q000379:methods*; D007763:Lac Operon; D008156:Luciferases / Q000235:genetics*; D049449:Luminescence; D008164:Luminescent Proteins; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence / Q000379:methods; D009369:Neoplasms / Q000628:therapy*; D014162:Transfection / Q000379:methods; D001616:beta-Galactosidase / Q000032:analysis
D005819:Genetic Markers; D008164:Luminescent Proteins; D008156:Luciferases; D001616:beta-Galactosidase