Allele-specific silencing of a pathogenic mutant acetylcholine receptor subunit by RNA interference.

Slow channel congenital myasthenic syndrome (SCCMS) is a disorder of the neuromuscular synapse caused by dominantly inherited missense mutations in genes that encode the muscle acetylcholine receptor (AChR) subunits. Here we investigate the potential of post-transcriptional gene silencing using RNA interference (RNAi) for the selective down-regulation of pathogenic mutant AChR. By transfection of both siRNA and shRNA into mammalian cells expressing wild-type or mutant AChR subunits, we show, using 125I-alpha-bungarotoxin binding and immunofluorescence to measure cell surface AChR expression, efficient discrimination between the silencing of alphaS226F AChR mutant RNA transcripts and the wild-type. In this model we find that selectivity between mutant and wild-type transcripts is optimized with the nucleotide mismatch at position 9 in the shRNA complementary sequence. We also find that allele-specific silencing using shRNA has comparable efficiency to that using siRNA, underlining the general potential of stable expression of shRNA molecules as a long term therapeutic approach for allele-specific silencing of mutant transcripts in dominant genetic disorders.