Functional correction of episomal mutations withshort DNA fragments and RNA–DNA oligonucleotides

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Abstract
Background Gene correction is an alternative approach to replacement gene therapy. By correcting mutations within the genome, some of the barriers to effective gene therapy are avoided. Homologous nucleic acid sequences can correct mutations by inducing recombination or mismatch repair. Recently, encouraging data have been presented using both short DNAfragments (SDFs) and RNA–DNA oligonucleotides (RDOs) in experimental strategies to realize clinical gene correction. Methods The delivery of labelled SDFs and RDOs to a variety of cell lines was tested using both FACS analysis and confocal microscopy. A GFP‐based reporter system was constructed, containing a nonsense mutation, to allow quantitation of gene correction in living cells. This reporter was used to compare efficiencies of functional gene correction using SDFs and RDOs in arange of mammalian cell lines. Results The delivery experiments highlight the inefficient delivery of SDFs and RDOs to the nucleus using polyethylenimine (PEI) transfection. This study compared the episomal correction efficiency of the reporter plasmid mediated by SDFs and RDOs within different cell types; low levels of functional correction were detected in cell culture. Conclusions Whilst delivery of PEI‐complexed SDFs or RDOs to the cell is highly effective, nuclear entry appears to be a limiting factor. SDFs elicited episomal GFP correction across a range of cell lines, whereas RDOs only corrected the reporter in a cell line that overexpresses RAD51. Copyright © 2002 John Wiley & Sons, Ltd.