| 1. |
- Bestas, Burcu, et al.
(författare)
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A Type II-B Cas9 nuclease with minimized off-targets and reduced chromosomal translocations in vivo
- 2023
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Ingår i: NATURE COMMUNICATIONS. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus pyogenes Cas9 (SpCas9) and derived enzymes are widely used as genome editors, but their promiscuous nuclease activity often induces undesired mutations and chromosomal rearrangements. Several strategies for mapping off-target effects have emerged, but they suffer from limited sensitivity. To increase the detection sensitivity, we develop an off-target assessment workflow that uses Duplex Sequencing. The strategy increases sensitivity by one order of magnitude, identifying previously unknown SpCas9's off-target mutations in the humanized PCSK9 mouse model. To reduce off-target risks, we perform a bioinformatic search and identify a high-fidelity Cas9 variant of the II-B subfamily from Parasutterella secunda (PsCas9). PsCas9 shows improved specificity as compared to SpCas9 across multiple tested sites, both in vitro and in vivo, including the PCSK9 site. In the future, while PsCas9 will offer an alternative to SpCas9 for research and clinical use, the Duplex Sequencing workflow will enable a more sensitive assessment of Cas9 editing outcomes. SpCas9 unintended editing is a major concern. Here the authors report an off-target method using Duplex Sequencing with increased sensitivity for Cas9 mutation detection; they also identify a Cas9 variant of the II-B subfamily with intrinsic high fidelity (PsCas9) and see improved specificity.
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| 2. |
- Bestas, Burcu
(författare)
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Design and application of RNA therapeutics for splice site mutations
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Precursor messenger RNA splicing is one of the most fundamental and complex mechanisms in eukaryotes. Over 90% of the human genes undergo alternative splicing, which is essential for the regulation of gene expression. A dynamic RNA-protein complex called the spliceosome catalyzes splicing. The spliceosome recognizes core splice site signals, and its function is furthermore regulated by other sequence elements that can either silence or enhance splicing in a cell-specific manner. These regulatory elements are recognized by trans-acting protein factors which modulate the function of the spliceosome. However, the fact that splicing is one of the most regulated mechanisms in the cell also makes it prone to dysfunctions caused by mutations. Mis-splicing diseases account for up to 30% of the inherited genetic diseases. They can be caused by mutations in the core splice sites as well as in the regulatory elements. Mutations that disrupt the splicing mechanism may result in RNA degradation, non-functional protein products, or toxic proteins that might alter the cellular environment. The understanding of mis-splicing disease mechanisms has been subject to various studies aiming at finding the appropriate therapeutics. In parallel with the development of gene therapy, where the classical aim is to introduce the corrected gene to cure a disease, another field has emerged; antisense oligonucleotide therapeutics. These RNA-DNA-based oligonucleotides can be designed to alter gene expression as well as to manipulate the splicing mechanism. Since their emergence during 1970s, antisense oligonucleotides have been extensively studied within the mis-splicing disease field, with several clinical trials ongoing. In this thesis, in paper I, we report a novel solid-phase synthesis method with a biological proof-of-concept. This synthesis method allows the conjugation of therapeutic oligonucleotides via a cleavable disulfide linker. The developed method can be applied to target several transcripts or different parts within the same transcript by allowing delivery of equimolar amounts of therapeutics. In paper II, we explore the possibility of using splice- correction approach for restoring the aberrant splicing of the gene BTK. Lack of BTK causes a primary immunodeficiency disease called XLA, which is a B cell developmental disorder. For the first time, we show splice-correction in B cells by modified oligonucleotide therapeutics both ex vivo and in vivo. In paper III, we aim at developing methods to rescue the core splice site mutations in BTK by using bifunctional oligonucleotide therapeutics. These oligonucleotides have the ability to recruit splice factor proteins, improving the splicing of mutated sites. We show that rescuing of core splice site mutations is possible yet it has its own challenges, which need to be taken into account in the design process. The results in this thesis have provided new therapeutics for a genetic disease, and more generally explores new methods for improving the function and delivery of oligonucleotide therapeutics.
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| 3. |
- Bestas, Burcu, et al.
(författare)
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Splice-correcting oligonucleotides restore BTK function in X-linked agammaglobulinemia model
- 2014
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Ingår i: Journal of Clinical Investigation. - 0021-9738 .- 1558-8238. ; 124:9, s. 4067-4081
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Tidskriftsartikel (refereegranskat)abstract
- X-linked agammaglobulinemia (XLA) is an inherited immunodeficiency that results from mutations within the gene encoding Bruton's tyrosine kinase (BTK). Many XLA-associated mutations affect splicing of BTK pre-mRNA and severely impair B cell development. Here, we assessed the potential of antisense, splice-correcting oligonucleotides (SCOs) targeting mutated BTKtranscripts for treating XLA. Both the SCO structural design and chemical properties were optimized using 2'-O-methyl, locked nucleic acid, or phosphorodiamidate morpholino backbones. In order to have access to an animal model of XLA, we engineered a transgenic mouse that harbors a BAC with an authentic, mutated, splice-defective human BTK gene. BTK transgenic mice were bred onto a Btk knockout background to avoid interference of the orthologous mouse protein. Using this model, we determined that BTK-specific SCOs are able to correct aberrantly spliced BTK in B lymphocytes, including pro-B cells. Correction of BTK mRNA restored expression of functional protein, as shown both by enhanced lymphocyte survival and reestablished BTK activation upon B cell receptor stimulation. Furthermore, SCO treatment corrected splicing and restored BTK expression in primary cells from patients with XLA. Together, our data demonstrate that SCOs can restore BTK function and that BTK-targeting SCOs have potential as personalized medicine in patients with XLA.
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| 4. |
- Ezzat, Kariem, et al.
(författare)
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The viral protein corona directs viral pathogenesis and amyloid aggregation
- 2019
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Artificial nanoparticles accumulate a protein corona layer in biological fluids, which significantly influences their bioactivity. As nanosized obligate intracellular parasites, viruses share many biophysical properties with artificial nanoparticles in extracellular environments and here we show that respiratory syncytial virus (RSV) and herpes simplex virus type 1 (HSV-1) accumulate a rich and distinctive protein corona in different biological fluids. Moreover, we show that corona pre-coating differentially affects viral infectivity and immune cell activation. In addition, we demonstrate that viruses bind amyloidogenic peptides in their corona and catalyze amyloid formation via surface-assisted heterogeneous nucleation. Importantly, we show that HSV-1 catalyzes the aggregation of the amyloid beta-peptide (A beta(42)), a major constituent of amyloid plaques in Alzheimer's disease, in vitro and in animal models. Our results highlight the viral protein corona as an acquired structural layer that is critical for viral-host interactions and illustrate a mechanistic convergence between viral and amyloid pathologies.
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| 5. |
- Sork, Helena, et al.
(författare)
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Lipid-based Transfection Reagents Exhibit Cryo-induced Increase in Transfection Efficiency
- 2016
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Ingår i: Molecular Therapy Nucleic Acids. - : Elsevier BV. - 2162-2531. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- The advantages of lipid-based transfection reagents have permitted their widespread use in molecular biology and gene therapy. This study outlines the effect of cryo-manipulation of a cationic lipid-based formulation, Lipofectamine 2000, which, after being frozen and thawed, showed orders of magnitude higher plasmid delivery efficiency throughout eight different cell lines, without compromising cell viability. Increased transfection efficiency with the freeze-thawed reagent was also seen with 2'-O-methyl phosphorothioate oligonucleotide delivery and in a splice-correction assay. Most importantly, a log-scale improvement in gene delivery using the freeze-thawed reagent was seen in vivo. Using three different methods, we detected considerable differences in the polydispersity of the different nucleic acid complexes as well as observed a clear difference in their surface spreading and sedimentation, with the freeze-thawed ones displaying substantially higher rate of dispersion and deposition on the glass surface. This hitherto overlooked elevated potency of the freeze-thawed reagent facilitates the targeting of hard-to-transfect cells, accomplishes higher transfection rates, and decreases the overall amount of reagent needed for delivery. Additionally, as we also saw a slight increase in plasmid delivery using other freeze-thawed transfection reagents, we postulate that freeze-thawing might prove to be useful for an even wider variety of transfection reagents.
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