RNA based gene therapy for dominantly inherited diseases

There are numerous examples in the literature of gene therapy applications for recessive disorders. There are precious few instances, however, of studies conducted to treat dominantly inherited pathologies. The reasons are simple: there are fewer cases of dominantly inherited diseases on one hand, but mostly it is far easier to correct recessive mutations than dominant ones. Typically recessive mutations cause a loss of (or reduced) gene function which can be compensated for by introduction of a replacement allele into the cell. In contrast, dominant negative mutations not only display impaired function, but also exhibit a novel one that is pathologic to the cell. Treating these conditions by gene therapy implies silencing the dominant allele without altering the expression of the wild-type gene. We describe here different strategies aimed at silencing dominant mutations through mRNA destruction and provide examples of their application to known autosomal dominant diseases. An overview of the most common molecular tools (antisense DNA and RNA, ribozymes and RNA interference) suitable to utilize these strategies is also presented and we discuss the relevant aspects involved in the choice of a particular approach in a gene therapy experiment.