Neuron-specific RNA interference using lentiviral vectors.

Background: Viral vectors have been used in several different settings for the delivery of small hairpin (sh) RNAs. However, most vectors have utilized ubiquitously-expressing polymerase (pol) III promoters to drive expression of the hairpin as a result of the strict requirement for precise transcriptional initiation and termination. Recently, pol II promoters have been used to construct vectors for RNA interference (RNAi). By embedding the shRNA into a micro RNA-context (miRNA) the endogenous miRNA processing machinery is exploited to achieve the mature synthetic miRNA (smiRNA), thereby expanding the possible promoter choices and eventually allowing cell type specific down-regulation of target genes.

Methods: In the present study, we constructed lentiviral vectors expressing smiRNAs under the control of pol II promoters to knockdown gene expression in cell culture and in the brain.

Results: We demonstrate robust knockdown of green fluorescent protein using lentiviral vectors driving RNAi from the ubiquitously-expressing promoter of the cytomegalovirus (CMV) and, in addition, we show for the first time neuron-specific knockdown in the brain using a neuron-specific promoter. Furthermore, we show that the expression pattern of the presumed ubiquitously-expressing CMV promoter changes over time from being expressed initially in neurons and glial cells to being expressed almost exclusively in neurons in later stages.

Conclusions: In the present study, we developed vectors for cell-specific RNAi for use in the brain. This offers the possibility of specifically targeting RNAi to a subset of cells in a complex tissue and may prove to be of great importance in the design of future gene therapeutic paradigms.