title: Synthesis of a probe for monitoring HSV1-tk reporter gene expression using chemical exchange saturation transfer MRI.
abstract: In experiments involving transgenic animals or animals treated with transgenic cells, it is important to have a method to monitor the expression of the relevant genes longitudinally and noninvasively. An MRI-based reporter gene enables monitoring of gene expression in the deep tissues of living subjects. This information can be co-registered with detailed high-resolution anatomical and functional information. We describe here the synthesis of the reporter probe, 5-methyl-5,6-dihydrothymidine (5-MDHT), which can be used for imaging of the herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene expression in rodents by MRI. The protocol also includes data acquisition and data processing routines customized for chemical exchange saturation transfer (CEST) contrast mechanisms. The dihydropyrimidine 5-MDHT is synthesized through a catalytic hydrogenation of the 5,6-double bond of thymidine to yield 5,6-dihydrothymidine, which is methylated on the C-5 position of the resulting saturated pyrimidine ring. The synthesis of 5-MDHT can be completed within 5 d, and the compound is stable for more than 1 year.
authors.affiliation: 1] Division of Magnetic Resonance Research, Russell H. Morgan Department of Radiology and Radiological Science, the Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. [2] Cellular Imaging Section and Vascular Biology Program, Institute for Cell Engineering, the Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors.forename: Amnon
authors.initials: A
authors.lastname: Bar-Shir
authors.forename: Guanshu
authors.initials: G
authors.lastname: Liu
authors.forename: Marc M
authors.initials: MM
authors.lastname: Greenberg
authors.forename: Jeff W M
authors.initials: JW
authors.lastname: Bulte
authors.forename: Assaf A
authors.initials: AA
authors.lastname: Gilad
mesh_terms: D000818:Animals; D017930:Genes, Reporter; D018259:Herpesvirus 1, Human / Q000201:enzymology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D012377:Rodentia / Q000821:virology; D013936:Thymidine / Q000031:analogs & derivatives / Q000032:analysis / Q000138:chemical synthesis / Q000737:chemistry; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000032:analysis
chemical_list: C109248:5,6-dihydro-5-methylthymidine; D014764:Viral Proteins; D013937:Thymidine Kinase; D013936:Thymidine