Abstract: Aspects of the present disclosure include methods of reducing the deleterious impact of a target gene in a cell, such as the deleterious activity of a mutant extended nucleotide repeat (NR) containing target gene in a cell by contacting the cell with an effective amount of a tetrahydrocarbazole compound. The deleterious activity (e.g., toxicity and/or dis-functionality of products encoded thereby) of a mutant extended NR containing target gene may be reduced, e.g., by reducing (and in some instances differentially, including selectively, reducing) the production or activity of toxic expression products (e.g., RNA or protein) encoded by the target gene. Kits and compositions for practicing the subject methods are also provided.