Assessment of allele-specific gene silencing by RNA interference with mutant and wild-type reporter alleles

Journal of RNAi and Gene Silencing 02/2006; 2(1):154-60.
Source: PubMed


Allele-specific gene silencing by RNA interference (RNAi) is therapeutically useful for specifically suppressing the expression of alleles associated with disease. To realize such allele-specific RNAi (ASPRNAi), the design and assessment of small interfering RNA (siRNA) duplexes conferring ASP-RNAi is vital, but is also difficult. Here, we show ASP-RNAi against the Swedish- and London-type amyloid precursor protein (APP) variants related to familial Alzheimer's disease using two reporter alleles encoding the Photinus and Renilla luciferase genes and carrying mutant and wild-type allelic sequences in their 3'-untranslated regions. We examined the effects of siRNA duplexes against the mutant alleles in allele-specific gene silencing and off-target silencing against the wild-type allele under heterozygous conditions, which were generated by cotransfecting the reporter alleles and siRNA duplexes into cultured human cells. Consistently, the siRNA duplexes determined to confer ASP-RNAi also inhibited the expression of the bona fide mutant APP and the production of either amyloid beta 40- or 42-peptide in Cos-7 cells expressing both the full-length Swedish- and wild-type APP alleles. The present data suggest that the system with reporter alleles may permit the preclinical assessment of siRNA duplexes conferring ASP-RNAi, and thus contribute to the design and selection of the most suitable of such siRNA duplexes.

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    • "For verifying efficacy of siRNA, we used mouse NIH3T3 embryonic fibroblast cell line (35 mm diameter), in which endogenous Col6a1 expression was quite low. The luciferase-based reporter alleles in phRL-TK (Renila luciferase) and pGL3-TK (Photinus luciferase) plasmids were generated according to previous report.25 The wild-type or mutated 31-bp sequences which contain each upstream and downstream 15-bp sequences around a mutation site in COL6A1 were inserted into 3′-untranslated region of luciferase genes (Figure 1b). "
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    ABSTRACT: Ullrich congenital muscular dystrophy (UCMD) is an inherited muscle disorder characterized clinically by muscle weakness, distal joint hyperlaxity, and proximal joint contractures. Sporadic and recessive mutations in the three collagen VI genes, COL6A1, COL6A2, and COL6A3, are reported to be causative. In the sporadic forms, a heterozygous point mutation causing glycine substitution in the triple helical domain has been identified in higher rate. In this study, we examined the efficacy of siRNAs, which target point mutation site, on specific knockdown toward transcripts from mutant allele and evaluated consequent cellular phenotype of UCMD fibroblasts. We evaluated the effect of siRNAs targeted to silence-specific COL6A1 alleles in UCMD fibroblasts, where simultaneous expression of both wild-type and mutant collagen VI resulted in defective collagen localization. Addition of mutant-specific siRNAs allowed normal extracellular localization of collagen VI surrounding fibroblasts, suggesting selective inhibition of mutant collagen VI. Targeting the single-nucleotide COL6A1 c.850G>A (p.G284R) mutation responsible a sporadic autosomal dominant form of UCMD can potently and selectively block expression of mutant collagen VI. These results suggest that allele-specific knockdown of the mutant mRNA can potentially be considered as a therapeutic procedure in UCMD due to COL6A1 point mutations.
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    • "There have been previously published reports of effective allele-specific siRNAs and shRNAs against genes linked to other neurodegenerative diseases, emphasizing the current interest and feasibility of this approach. Some examples include: ataxin 7 (spinocerebellar ataxia type 7; [37]), ataxin 3 (Machado-Joseph disease; [36], [58]), amyloid precursor protein APP (Alzheimer's disease; [59], [60], [61], [62]), prion protein (Creutzfeldt-Jakob disease; [63]), and huntingtin (Huntington's disease; [40], [42], [64], [65], [66]) and the Cu/Zn superoxide dismutase gene SOD1 (hereditary amyotrophic lateral sclerosis ALS; [40], [44], [45], [46], [67], [68], [69]). "
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    PLoS ONE 06/2011; 6(6):e21352. DOI:10.1371/journal.pone.0021352 · 3.23 Impact Factor
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    • "and forked (Fork) siRNA duplexes. Assessment of conventional and forked siRNA duplexes against the London V717I (B), V717F (C), and V717G (D) APP mutants and the Swedish (E) APP mutant was carried out as described previously [17]. The ratios of mutant and wild-type luciferase activities in the presence of siRNA duplexes were normalized against the control ratio obtained in the presence of siControl duplex. "
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    ABSTRACT: Allele-specific gene silencing by RNA interference (RNAi) is therapeutically useful for specifically inhibiting the expression of disease-associated alleles without suppressing the expression of corresponding wild-type alleles. To realize such allele-specific RNAi (ASP-RNAi), the design and assessment of small interfering RNA (siRNA) duplexes conferring ASP-RNAi is vital; however, it is also difficult. In a previous study, we developed an assay system to assess ASP-RNAi with mutant and wild-type reporter alleles encoding the Photinus and Renilla luciferase genes. In line with experiments using the system, we realized that it is necessary and important to enhance allele discrimination between mutant and corresponding wild-type alleles. Here, we describe the improvement of ASP-RNAi against mutant alleles carrying single nucleotide variations by introducing base substitutions into siRNA sequences, where original variations are present in the central position. Artificially mismatched siRNAs or short-hairpin RNAs (shRNAs) against mutant alleles of the human Prion Protein (PRNP) gene, which appear to be associated with susceptibility to prion diseases, were examined using this assessment system. The data indicates that introduction of a one-base mismatch into the siRNAs and shRNAs was able to enhance discrimination between the mutant and wild-type alleles. Interestingly, the introduced mismatches that conferred marked improvement in ASP-RNAi, appeared to be largely present in the guide siRNA elements, corresponding to the 'seed region' of microRNAs. Due to the essential role of the 'seed region' of microRNAs in their association with target RNAs, it is conceivable that disruption of the base-pairing interactions in the corresponding seed region, as well as the central position (involved in cleavage of target RNAs), of guide siRNA elements could influence allele discrimination. In addition, we also suggest that nucleotide mismatches at the 3'-ends of sense-strand siRNA elements, which possibly increase the assembly of antisense-strand (guide) siRNAs into RNA-induced silencing complexes (RISCs), may enhance ASP-RNAi in the case of inert siRNA duplexes. Therefore, the data presented here suggest that structural modification of functional portions of an siRNA duplex by base substitution could greatly influence allele discrimination and gene silencing, thereby contributing to enhancement of ASP-RNAi.
    PLoS ONE 02/2008; 3(5):e2248. DOI:10.1371/journal.pone.0002248 · 3.23 Impact Factor
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