title: In vivo optical imaging of LacZ expression using lacZ transgenic mice.
abstract: beta-Galactosidase (beta-gal) (encoded by the lacZ gene) has been widely used as a transgene reporter enzyme. The ability to image lacZ expression in living transgenic animals would further extend the use of this reporter. It has been reported that 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one)-beta-d-galactopyranoside (DDAOG), a conjugate of beta-galactose and 7-hydroxy-9H-(1,3-dichloro-9,9-dimethylacridin-2-one), is not only a chromogenic lacZ substrate but that the cleavage product has far-red fluorescence properties detectable by in vivo imaging. In an attempt to noninvasively image lacZ expression in vivo, we applied fluorescence imaging to a G protein-coupled receptor (GPR56), knockout (KO) mouse model, in which the lacZ gene is introduced in the GPR56 locus. Compared to wild-type (WT) mice, GPR56KO/LacZ mice showed three- to fourfold higher fluorescence intensity in the head area 5 min after tail-vein injection of DDAOG. beta-Gal staining in sections of whole brain showed strong lacZ expression in homozygotes, but not in WT mice, consistent with lacZ activity detected by in vivo imaging. The kidneys were also visualized with fluorescence imaging both in vivo and ex vivo, consistent with beta-gal staining findings. Our results demonstrate that fluorescence imaging can be used for in vivo real-time detection of lacZ activity by fluorescence imaging in lacZ transgenic mice. Thus, this technology can potentially be used to noninvasively image changes of certain endogenous molecules and/or molecular pathways in transgenic animals.
authors.affiliation: Imaging, Merck Research Laboratories, West Point, Pennsylvania 19486, USA. guoj_zhang@yahoo.com
authors.forename: Guo-Jun
authors.initials: GJ
authors.lastname: Zhang
authors.forename: Tsing-Bau
authors.initials: TB
authors.lastname: Chen
authors.forename: Brett
authors.initials: B
authors.lastname: Connolly
authors.forename: Shu-An
authors.initials: SA
authors.lastname: Lin
authors.forename: Richard
authors.initials: R
authors.lastname: Hargreaves
authors.forename: Amy
authors.initials: A
authors.lastname: Vanko
authors.forename: Bohumil
authors.initials: B
authors.lastname: Bednar
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: Macneil
authors.forename: Cyrille
authors.initials: C
authors.lastname: Sur
authors.forename: David L
authors.initials: DL
authors.lastname: Williams
mesh_terms: D000818:Animals; D004396:Coloring Agents; D005696:Galactosidases / Q000737:chemistry; D015870:Gene Expression / Q000235:genetics*; D007091:Image Processing, Computer-Assisted; D007763:Lac Operon / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D010641:Phenotype; D043562:Receptors, G-Protein-Coupled / Q000235:genetics; D012815:Signal Processing, Computer-Assisted; D014162:Transfection; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D004396:Coloring Agents; D005696:Galactosidases; D043562:Receptors, G-Protein-Coupled; D001616:beta-Galactosidase; C524781:Adgrg1 protein, mouse