Lentiviral Vectors with Amplified Beta Cell-Specific Gene Expression

An important goal of gene therapy is to be able to deliver genes so that they express in a pattern that recapitulates the expression of an endogenous cellular gene. Although tissue-specific promoters confer selectivity, in a vector-based system, their activity may be too weak to mediate detectable levels in gene expression studies. We have used a two-step transcriptional activator (TSTA) system to amplify gene expression from lentiviral vectors using the human insulin promoter (HIP). In this system, the HIP drives expression of a potent synthetic transcription activator (the yeast GAL4 DNA binding domain fused to the activation domain of the HSV-1 VP16 activator), which in turn activates a GAL4-responsive promoter driving the enhanced green fluorescent protein reporter gene. Vectors carrying the HIP did not express in non-β cell lines but expressed in murine insulinoma cell lines, indicating that the HIP was capable of conferring cell specificity of expression. The insulin amplifiable-vector was able to amplify gene expression five to nine times over a standard insulin promoter vector. In primary human islets, gene expression from the insulin-promoted vectors was coincident with insulin staining. These vectors will be useful in gene expression studies that require a detectable signal and tissue specificity.