Chimeric RNA/DNA oligonucleotide-based gene therapy.

Abstract

Chimeric RNA/DNA oligonucleotides, emerging as a potential strategy for gene therapy, have been shown to induce site-specific correction of point mutations in several genetic disease models. Six recent studies of chimeric RNA/DNA oligonucleotide-based gene therapy in genetic disease models are reviewed. Chimeric RNA/DNA oligonucleotides, complementary to 25 to 30 residues of genomic DNA flanking the mutation site with the exception of a mismatch in the center, were delivered via different routes and delivery vehicles to target different tissues and organs. Corrections of the mutation at genotypic and phenotypic levels were assessed using various methods, including allele-specific polymerase chain reaction assay, restriction enzyme digestion, colony-lifting assays, sequencing, Northern and Western blot analyses, enzyme activity assay, immunohistochemical staining, and functional studies. The gene correction frequency varied, ranging from less than 1% to more than 40%. This represented several magnitudes higher conversion rate compared with homologous recombination frequency, which is in the range of 10(-5) to 10(-6). The resulting phenotype changes lasted longer than one year in some studies. Chimeric RNA/DNA oligonucleotide-based gene therapy has the potential to develop into powerful therapeutic modality for genetic diseases. It can offer permanent expression and normal regulation of corrected genes in appropriate cells or tissues. Further efforts to elucidate the mechanisms of chimeric RNA/DNA oligonucleotide-based gene therapy are warranted in order to increase the efficacy and safety of this method.