Differential expression of tissue-specific promoters by gene gun

Background Tissue-specific promoters are becoming increasingly important in light of their effects on gene expression in gene therapy experiments. The regulation of gene expression may be as important as the delivery of the g ene itself. Objectives To determine the effects of the involucrin (INV), keratin 14 (K1 4) and cytomegalovirus (CMV) promoters on the expression of the reporter ge ne beta -galactosidase. Methods In vivo, plasmid DNA was introduced to BALB/c mice by gene gun. Ski n biopsies were taken after 24 h for histology and beta -galactosidase stai ning. In tissue culture cells, plasmid DNA was introduced by transient tran sfection to cell lines 293 (transformed primary human embryonal kidney cell s), NIH 3T3 (immortalized mouse fibroblasts) and human keratinocytes. Repor ter gene expression was assayed by histochemical staining and chemiluminesc ence. Results The K14 and INV promoter constructs showed beta -galactosidase gene expression only in the epidermis, while the CMV promoter showed gene expre ssion in both the dermis and epidermis. In cell culture, the INV and K14 pr omoter constructs demonstrated significant beta -galactosidase expression i n human keratinocytes, but minimal expression in 293 and NIH 3T3 cell types . CMV promoter constructs demonstrated significant expression in all cell t ypes. Conclusions Gene expression can be regulated by different promoters both in vivo and in cell culture. Based on the physiological expression of the dif ferent promoters, gene expression can be restricted to certain cell types, tissues and skin layers.