Abstract #1725

Genetic Engineering of Human Protamine-1 for Use as MRI Reporter Gene Based on Proton Exchange

Amnon Bar-Shir^1,2, Guanshu Liu^1,3, Xiaolei Song^1,2, Piotr Walczak^1,2, Michael T. McMahon^1,3, Peter C. van Zijl^1,3, Jeff W. Bulte^1,2, Assaf A. Gilad^1,2

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.