Gene correction by RNA-DNA oligonucleotides

An oligonucleotide composed of a contiguous stretch of RNA and DNA residues has been developed to facilitate the correction of single-base mutations o f episomal and chromosomal targets in mammalian cells. The design of the ol igonucleotide exploited the highly recombinogenic RNA-DNA hybrids and featu red hairpin capped ends avoiding destruction by cellular helicases or exonu cleases. The RNA-DNA oligonucleotide (RDO) was designed to correct a point mutation in the tyrosinase gene and caused a permanent gene correction in m ouse albino melanocytes, determined by clonal analysis at the level of geno mic sequence, protein and phenotypic change. Recently, we demonstrated corr ection of the tyrosinase gene using the same RDO in vivo, as detected by da rk pigmentation of several hairs and DOPA staining of hair follicles in the treated skin of albino mice. Such RDOs might hold a promise as a therapeut ic method for the treatment of skin diseases. However, the frequency of gen e correction varies among different cells, indicating that cellular activit ies, such as recombination and repair, may be important for gene conversion by RDOs, As this technology becomes more widely utilized in the scientific community, it mill be important to understand the mechanism and to optimiz e the design of RDOs to improve their efficiency and general applicability.