Investigation of RNA interference to suppress expression of full-length and fragment human huntingtin

The use of RNAinterference (RNAi) to suppress the expression of genes has drastically improved the ability to examine gene function and is now being considered as a therapeutic approach for many diseases including genetic forms of neurodegenerative disease. Recently, research has focused on RNAi for the treatment of Huntington's and other polyglutamine diseases. In this work we explored the efficacy and specificity of short hairpin RNAs to target human huntingtin mRNA. We found two sequences that are specific for, and efficiently suppress human huntingtin mRNA. Mouse cell lines that stably harbored human short hairpin RNA constructs specifically inhibited the expression of human huntingtin supplied by transfected expression plasmids. However, these same constructs were unable to stably suppress endogenous human huntingtin when stably transfected into human 293 cells, despite effectively knocking down expression of huntingtin in transient transfection. These results demonstrate the efficacy and specificity of RNAi as a tool to target human huntingtin in RNAi-based therapies but point toward potential problems, possibly cell-type specific, regarding stable suppression of human huntingtin.