Selective silencing by RNAi of a dominant allele that causes amyotrophic lateral sclerosis

Abstract

Summary: RNA interference (RNAi) can achieve sequence‐selective inactivation of gene expression in a wide variety of eukaryotes by introducing double‐stranded RNA corresponding to the target gene. Here we explore the potential of RNAi as a therapy for amyotrophic lateral sclerosis (ALS) caused by mutations in the Cu, Zn superoxide dismutase (SOD1) gene. Although the mutant SOD1 is toxic, the wild‐type SOD1 performs important functions. Therefore, the ideal therapeutic strategy should be to selectively inhibit the mutant, but not the wild‐type SOD1 expression. Because most SOD1 mutations are single nucleotide changes, to selectively silence the mutant requires single‐nucleotide specificity. By coupling rational design of small interfering RNAs (siRNAs) with their validation in RNAi reactions in vitro and in vivo, we have identified siRNA sequences with this specificity. A similarly designed sequence, when expressed as small hairpin RNA (shRNA) under the control of an RNA polymerase III (pol III) promoter, retains the single‐nucleotide specificity. Thus, RNAi is a promising therapy for ALS and other disorders caused by dominant, gain‐of‐function gene mutations.