Project description:we introduce a strategy to repurpose sense-codon decoding tRNA into efficient suppressors of the three nonsense mutation-induced PTCs (UGA, UAG and UAA). The suppressor tRNAs restore function of a model and disease-related protein
Project description:Missense mutations account for nearly 50% of pathogenic mutations in human genetic diseases, most lack effective treatments. Gene therapies, CRISPR-based gene editing, and RNA therapies including transfer RNA (tRNA) modalities are common strategies for potential treatments of genetic diseases. However, reported tRNA therapies are for nonsense mutations, how tRNAs can be engineered to correct missense mutations have not been explored. Here, we describe missense correcting tRNAs (mc-tRNAs) as a potential therapeutic modality for correcting pathogenic missense mutations. Mc-tRNAs are engineered tRNAs that are charged with one amino acid and read codons of another amino acid in translation in human cells. We first developed a series of fluorescence protein (FP)-based reporters that indicate successful correction of missense mutations via restoration of fluorescence signals. We engineered mc-tRNAs that effectively corrected Serine and Arginine missense mutations in the reporters and confirmed the amino acid substitution by protein mass spectrometry and mc-tRNA expression by tRNA sequencing. We examined the transcriptome response to the expression of mc-tRNAs and found some mc-tRNAs induced minimum transcriptomic changes. Furthermore, we applied an Arg-tRNAGln(CUG) mc-tRNA to rescue the autolytic activity of a pathogenic CAPN3 Arg-to-Gln mutant involved in limb-girdle muscular dystrophy type 2A. These results establish a versatile pipeline for mc-tRNA engineering and demonstrate the potential of mc-tRNA as an alternative therapeutic platform for the treatment of genetic disorders.
Project description:Missense mutations account for nearly 50% of pathogenic mutations in human genetic diseases, most lack effective treatments. Gene therapies, CRISPR-based gene editing, and RNA therapies including transfer RNA (tRNA) modalities are common strategies for potential treatments of genetic diseases. However, reported tRNA therapies are for nonsense mutations, how tRNAs can be engineered to correct missense mutations have not been explored. Here, we describe missense correcting tRNAs (mc-tRNAs) as a potential therapeutic modality for correcting pathogenic missense mutations. Mc-tRNAs are engineered tRNAs that are charged with one amino acid and read codons of another amino acid in translation in human cells. We first developed a series of fluorescence protein (FP)-based reporters that indicate successful correction of missense mutations via restoration of fluorescence signals. We engineered mc-tRNAs that effectively corrected Serine and Arginine missense mutations in the reporters and confirmed the amino acid substitution by protein mass spectrometry and mc-tRNA expression by tRNA sequencing. We examined the transcriptome response to the expression of mc-tRNAs and found some mc-tRNAs induced minimum transcriptomic changes. Furthermore, we applied an Arg-tRNAGln(CUG) mc-tRNA to rescue the autolytic activity of a pathogenic CAPN3 Arg-to-Gln mutant involved in limb-girdle muscular dystrophy type 2A. These results establish a versatile pipeline for mc-tRNA engineering and demonstrate the potential of mc-tRNA as an alternative therapeutic platform for the treatment of genetic disorders.
Project description:Nonsense mutations - the underlying cause of approximately 11% of all genetic diseases - prematurely terminate protein synthesis by mutating a sense codon to a premature stop or termination codon (PTC). An emerging therapeutic strategy to suppress nonsense defects is to engineer sense-codon decoding tRNAs to readthrough and restore translation at PTCs. However, the readthrough efficiency of the engineered suppressor tRNAs (sup-tRNAs) largely varies in a tissue- and sequence context-dependent manner and has not yet yielded optimal clinical efficacy for many nonsense mutations. Here, we systematically analyze the suppression efficacy at various pathogenic nonsense mutations. We discover that the translation velocity of the sequence upstream of PTCs modulates the sup-tRNA readthrough efficacy. The PTCs most refractory to suppression are embedded in a sequence context translated with an abrupt reversal of the translation speed leading to ribosomal collisions. Moreover, modeling translation velocity using Ribo-seq data can accurately predict the suppression efficacy at PTCs. These results reveal previously unknown molecular signatures contributing to genotype-phenotype relationships and treatment-response heterogeneity, and provide the framework for the development of personalized tRNA-based gene therapies.
Project description:A large number of genetic diseases are caused by various mutations in specific disease genes. A significant proportion (~15%) of these mutations are nonsense mutations that create a premature termination codon (PTC). Consequently, the Nonsense-mediated mRNA Decay (NMD) surveillance pathway degrades a large fraction of PTC-containing mRNA. Translation of the remaining un-degraded PTC-containing mRNA terminates at the PTC, leading to no full-length protein production and hence disease. Therefore, suppressing NMD and translation termination at PTCs becomes an attractive strategy for combating these diseases. This work presents a novel approach, namely targeted PTC pseudouridylation, to suppress nonsense mutations in human cells. By co-transfecting human cells with a PTC-reporter gene and a designer box H/ACA guide RNA gene targeting the PTC, we show that targeted pseudouridylation suppresses both NMD and translation termination at PTCs in the contexts of various disease gene sequences. Furthermore, targeted pseudouridylation exhibits a level of suppression comparable to that of antibiotic treatments, and the suppressive effect is long-lasting in the cell. When targeted pseudouridylation is combined with the antibiotic treatment, a much higher level of suppression is observed. Remarkably, by transfecting a disease model cell line (carrying a chromosomal PTC) with a designer guide RNA gene alone targeting the PTC, we also observe nonsense suppression, suggesting the high potential of this novel approach in treating PTC-associated diseases. Finally, one of the restored full-length proteins is further tested to be functional. Targeted pseudouridylation appears to be the first RNA-directed gene-specific therapeutic approach that suppresses NMD and concurrently promotes PTC read-through.
Project description:PTCs cause a multitude of human diseases and there are no established therapeutic options for their therapeutic management. Herein, we report the high-throughput cloning and identification, characterization and functional analysis of anticodon-edited tRNA which display efficacious PTC reversion in eukaryotic cells and mouse skeletal muscle. Notably, our screen identifies ACE-tRNA, in total, with the potential to repair a vast majority of known human disease-causing PTC, but this therapeutic will require overcoming tissue and delivery specific challenges. However, the engineered tRNA, once delivered, faithfully encode their cognate amino acid, thus abrogating spurious effects on downstream protein stability, folding, and trafficking, and consequently negating the need for tandem therapies involving protein folding or trafficking agents. When transfected as cDNA, ACE-tRNAs rescued multiple full-length proteins via PTC suppression; a NLuc luciferase reporter, a model protein HDH, and two disease nonsense mutations in CFTR.