title: MRI-based detection of alkaline phosphatase gene reporter activity using a porphyrin solubility switch.
abstract: The ability to map patterns of gene expression noninvasively in living animals could have impact in many areas of biology. Reporter systems compatible with MRI could be particularly valuable, but existing strategies tend to lack sensitivity or specificity. Here we address the challenge of MRI-based gene mapping using the reporter enzyme secreted alkaline phosphatase (SEAP), in conjunction with a water-soluble metalloporphyrin contrast agent. SEAP cleaves the porphyrin into an insoluble product that accumulates at sites of enzyme expression and can be visualized by MRI and optical absorbance. The contrast mechanism functions in vitro, in brain slices, and in animals. The system also provides the possibility of readout both in the living animal and by postmortem histology, and it notably does not require intracellular delivery of the contrast agent. The solubility switch mechanism used to detect SEAP could be adapted for imaging of additional reporter enzymes or endogenous targets.
authors.affiliation: Departments of Brain & Cognitive Sciences, Biological Engineering, and Nuclear Science & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 16-561, Cambridge, MA 02139, USA; Department of Nuclear Medicine, Technische Universität München, 81675 Munich, Germany; Institutes of Biological and Medical Imaging and Developmental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Munich/Neuherberg, Germany.
authors.forename: Gil G
authors.initials: GG
authors.lastname: Westmeyer
authors.affiliation: Departments of Brain & Cognitive Sciences, Biological Engineering, and Nuclear Science & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 16-561, Cambridge, MA 02139, USA.
authors.forename: Yelena
authors.initials: Y
authors.lastname: Emer
authors.affiliation: Comprehensive Molecular Analytics Cooperation Group, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Munich/Neuherberg, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Lintelmann
authors.affiliation: Departments of Brain & Cognitive Sciences, Biological Engineering, and Nuclear Science & Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 16-561, Cambridge, MA 02139, USA. Electronic address: jasanoff@mit.edu.
authors.forename: Alan
authors.initials: A
authors.lastname: Jasanoff
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D003287:Contrast Media / Q000737:chemistry / Q000378:metabolism; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
chemical_list: D003287:Contrast Media; D011166:Porphyrins; D020033:Protein Isoforms; D000469:Alkaline Phosphatase