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We evaluate a knockdown-replacement strategy mediated by mirtrons as an alternative to allele-specific silencing using spinocerebellar ataxia 7 (SCA7) as a model. Mirtrons are introns that form pre-microRNA hairpins after splicing, producing RNAi effectors not processed by Drosha. Mirtron mimics may therefore avoid saturation of the canonical processing pathway. This method combines gene silencing mediated by an artificial mirtron with delivery of a functional copy of the gene such that both elements of the therapy are always expressed concurrently, minimizing the potential for undesirable effects and preserving wild-type function. This mutation- and single nucleotide polymorphism-independent method could be crucial in dominant diseases that feature both gain- and loss-of-function pathologies or have a heterogeneous genetic background. Here we develop mirtrons against ataxin 7 with silencing efficacy comparable to shRNAs, and introduce silent mutations into an ataxin 7 transgene such that it is resistant to their effect. We successfully express the transgene and one mirtron together from a single construct. Hence, we show that this method can be used to silence the endogenous allele of ataxin 7 and replace it with an exogenous copy of the gene, highlighting the efficacy and transferability across patient genotypes of this approach.

Original publication

DOI

10.1093/nar/gkx483

Type

Journal article

Journal

Nucleic Acids Res

Publication Date

27/07/2017

Volume

45

Pages

7870 - 7885

Keywords

Ataxin-7, Cell Line, Gene Knockdown Techniques, Genetic Therapy, HEK293 Cells, Humans, Introns, MicroRNAs, Models, Genetic, RNA Interference, RNA Precursors, RNA Processing, Post-Transcriptional, RNA Splicing, Spinocerebellar Ataxias, Transfection