Amnon Bar-Shir1,2, Guanshu Liu1,3,
Xiaolei Song1,2, Piotr Walczak1,2, Michael T. McMahon1,3,
Peter C. van Zijl1,3, Jeff W. Bulte1,2, Assaf A. Gilad1,2
1Division of MR Research,
The Russel H. Morgan Department of Radiology, The Johns Hopkins University
School of Medicine, Baltimore, MD, United States; 2Cellular
Imaging Section, Institute for Cell Engineering, The Johns Hopkins University
School of Medicine, Baltimore, MD, United States; 3F.M. Kirby
Research Center for Functional Brain Imaging, Kennedy Krieger Institute,
Baltimore, MD, United States
Several strategies for MR imaging of gene expression have been developed, each with its own specific contrast mechanism to generate signal from reporter genes. Here, we demonstrate that human protamine-1 (hPRM1), an arginine-rich protein, generates superior MRI contrast based on the chemical exchange saturation transfer (CEST) mechanism. To this end, recombinant hPRM1 was engineered to be expressed in E. coli. The dialyzed bacterial lysate showed a much higher CEST contrast as compared to control proteins, suggesting that hPRM1 is a promising new CEST reporter gene.