As a molecular biologist, I am interested in gene expression in cells of the islets of Langerhans, particularly as it pertains to insulin secretion and proliferation (1,2,3,4,5,6,7) To study islet gene function, it is often useful to overexpress or silence genes, yet islet and islet-derived cells are poorly transduced by traditional transfection methods. Fortunately, these cells are readily transduced by recombinant adenoviruses (1) (Figure 1), which have proven themselves to be powerful tools for islet studies. As such, I have had a long-standing interest in developing gene expression tools and expanding the versatility of existing adenoviral systems.
The first generation adenoviral shuttle vector pAC.CMV (1)(Figure 2), limited the user to overexpression (OE) of cDNAs in a constitutive non-cell-type specific manner. To overcome this limited use, we modified this first generation shuttle vector by replacing the CMV promoter with the rat insulin I promoter (RIP), allowing genes to be expressed only in transduced beta cells (Figure 2). In parallel, we also generated a corresponding RNAi shuttle vector to silence target genes in transduced cells (8,9)(Figure 2).
Second generation adenviral systems, such as the AdEasy system (Figure 3) have become popular. To enhance the versatility of this system, we recently developed a versatile shuttle vector system that functions as an OE and an RNAi vector, allowing users to inducibly express cDNAs, microRNAs and/or shRNAs in a cell-specific or non-specific manner (Figures 4 & 5). The cell-specific promoter in this shuttle system is also designed to be easily substituted for one’s cell-specific promoter of choice. The system also allows users to constitutively express the EGFP marker in transduced cells if needed.
Given the power and versatility of the recombinant adenovirus platform, we hope further development will benefit islet researchers as well as researchers in other fields.