A novel strategy for monitoring the location of a transgene in a mammal is
disclosed. A sodium iodide symporter is genetically fused to either the
N-terminus or C-terminus of the product of a transgene through a linker
peptide which bears the recognition sequence of a host cell protease.
Expression of the transgene confers the activity of the sodium iodide
symporter (NIS)to a host cell which expresses the transgene. Subsequent
administration of labeled iodine results in transport of the labeled
iodine into the cell bearing the NIS, which can then be localized and
measured using standard imaging techniques. The system is particularly
useful for monitoring the location of therapeutic transgenes and
tissue-specific distribution of the therapeutic gene product.