Suppression of Somatic Expansion As a Novel Therapeutic Approach for Huntington Disease and Other Repeat Expansion Disorders

Huntington disease (HD) is one of a growing number of rare genetic diseases characterized by the inheritance of an increased number of short tandem repeats within the affected gene. Many of these repeat expansion disorders (REDs) affect the brain. Although inheritance of the mutant allele is a necessary first step for disease manifestation, a second step of further expansion of the inherited expanded repeats, particularly in neurons in the brain, also appears to play a critical role toward disease manifestation. This dynamic process, called somatic expansion, is modulated by genes involved in the repair of DNA that operate upstream of the specific gene associated with each individual disease. As somatic expansion has been described in multiple REDs, genes associated with regulating somatic expansion are attractive therapeutic targets, since multiple REDs could potentially be treated with the same drug.