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Simplifying plant gene silencing and genome editing logistics by a one-Agrobacterium system for simultaneous delivery of multipartite virus vectors.
Viral vectors provide a quick and effective way to express exogenous sequences in eukaryotic cells and to engineer eukaryotic genomes through the delivery of CRISPR/Cas components. Here, we present JoinTRV, an improved vector system based on tobacco rattle virus (TRV) that simplifies gene silencing and genome editing logistics. Our system consists of two mini T-DNA vectors from which TRV RNA1 (pLX-TRV1) and an engineered version of TRV RNA2 (pLX-TRV2) are expressed. The two vectors have compatible origins that allow their cotransformation and maintenance into a single Agrobacterium cell, as well as their simultaneous delivery to plants by a one-Agrobacterium/two-vector approach. The JoinTRV vectors are substantially smaller than those of any known TRV vector system, and pLX-TRV2 can be easily customized to express desired sequences by one-step digestion-ligation and homology-based cloning. The system was successfully used in Nicotiana benthamiana for launching TRV infection, for recombinant protein production, as well as for robust virus-induced gene silencing (VIGS) of endogenous transcripts using bacterial suspensions at low optical densities. JoinTRV-mediated delivery of single-guide RNAs in a Cas9 transgenic host allowed somatic cell editing efficiencies of ≈90%; editing events were heritable and >50% of the progeny seedlings showed mutations at the targeted loci.
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[Genome Editing with CRISPR/Cas9: First Steps Towards a new Era in Medicine?].
The emergence of genome editing technologies can be regarded as one of the most groundbreaking revolutions in the history of science. Modern genome editing allows the introduction of precise mutations into the genome of virtually all cells and organisms without leaving any additional trace. Undoubtedly, genome editing with CRISPR/Cas9, often casually referred to as "genetic scissors", will revolutionize medical research and development. However, at the same time it creates a great need for ethical considerations as it might hold risks for both people and the environment that cannot yet be fully assessed. While genome editing is already well established in laboratory research, clinical applications based on genome editing are close. For the first time, targeted corrections of genetic defects in somatic cells, stem cells as well as in the germ line appear technically feasible. This generates possible future scenarios that urgently require broad ethical and social discussions.
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A pipeline for rapidly generating genetically engineered mouse models of pancreatic cancer using in vivo CRISPR-Cas9-mediated somatic recombination.
Genetically engineered mouse models (GEMMs) that recapitulate the major genetic drivers in pancreatic ductal adenocarcinoma (PDAC) have provided unprecedented insights into the pathogenesis of this lethal neoplasm. Nonetheless, generating an autochthonous model is an expensive, time consuming and labor intensive process, particularly when tissue specific expression or deletion of compound alleles are involved. In addition, many of the current PDAC GEMMs cause embryonic, pancreas-wide activation or loss of driver alleles, neither of which reflects the cognate human disease scenario. The advent of CRISPR/Cas9 based gene editing can potentially circumvent many of the aforementioned shortcomings of conventional breeding schema, but ensuring the efficiency of gene editing in vivo remains a challenge. Here we have developed a pipeline for generating PDAC GEMMs of complex genotypes with high efficiency using a single "workhorse" mouse strain expressing Cas9 in the adult pancreas under a p48 promoter. Using adeno-associated virus (AAV) mediated delivery of multiplexed guide RNAs (sgRNAs) to the adult murine pancreas of p48-Cre; LSL-Cas9 mice, we confirm our ability to express an oncogenic Kras G12D allele through homology-directed repair (HDR), in conjunction with CRISPR-induced disruption of cooperating alleles (Trp53, Lkb1 and Arid1A). The resulting GEMMs demonstrate a spectrum of precursor lesions (pancreatic intraepithelial neoplasia [PanIN] or Intraductal papillary mucinous neoplasm [IPMN] with eventual progression to PDAC. Next generation sequencing of the resulting murine PDAC confirms HDR of oncogenic KrasG12D allele at the endogenous locus, and insertion deletion ("indel") and frameshift mutations of targeted tumor suppressor alleles. By using a single "workhorse" mouse strain and optimal AAV serotype for in vivo gene editing with combination of driver alleles, we present a facile autochthonous platform for interrogation of the PDAC genome.
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Nonviral gene editing via CRISPR/Cas9 delivery by membrane-disruptive and endosomolytic helical polypeptide.
Effective and safe delivery of the CRISPR/Cas9 gene-editing elements remains a challenge. Here we report the development of PEGylated nanoparticles (named P-HNPs) based on the cationic α-helical polypeptide poly(γ-4-((2-(piperidin-1-yl)ethyl)aminomethyl)benzyl-l-glutamate) for the delivery of Cas9 expression plasmid and sgRNA to various cell types and gene-editing scenarios. The cell-penetrating α-helical polypeptide enhanced cellular uptake and promoted escape of pCas9 and/or sgRNA from the endosome and transport into the nucleus. The colloidally stable P-HNPs achieved a Cas9 transfection efficiency up to 60% and sgRNA uptake efficiency of 67.4%, representing an improvement over existing polycation-based gene delivery systems. After performing single or multiplex gene editing with an efficiency up to 47.3% in vitro, we demonstrated that P-HNPs delivering Cas9 plasmid/sgRNA targeting the polo-like kinase 1 (Plk1) gene achieved 35% gene deletion in HeLa tumor tissue to reduce the Plk1 protein level by 66.7%, thereby suppressing the tumor growth by >71% and prolonging the animal survival rate to 60% within 60 days. Capable of delivering Cas9 plasmids to various cell types to achieve multiplex gene knock-out, gene knock-in, and gene activation in vitro and in vivo, the P-HNP system offers a versatile gene-editing platform for biological research and therapeutic applications.
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Advances in genome editing: the technology of choice for precise and efficient β-thalassemia treatment.
Beta (β)-thalassemia is one of the most significant hemoglobinopathy worldwide. The high prevalence of the β-thalassemia carriers aggravates the disease burden for patients and national economies in the developing world. The survival of β-thalassemia patients solely relies on repeated transfusions, which eventually results into multi-organ damage. The fetal γ-globin genes are ordinarily silenced at birth and replaced by the adult β-globin genes. However, mutations that cause lifelong persistence of fetal γ-globin, ameliorate the debilitating effects of β-globin mutations. Therefore, therapeutically reactivating the fetal γ-globin gene is a prime focus of researchers. CRISPR/Cas9 is the most common approach to correct disease causative mutations or to enhance or disrupt the expression of proteins to mitigate the effects of the disease. CRISPR/cas9 and prime gene editing to correct mutations in hematopoietic stem cells of β-thalassemia patients has been considered a novel therapeutic approach for effective hemoglobin production. However, genome-editing technologies, along with all advantages, have shown some disadvantages due to either random insertions or deletions at the target site of edition or non-specific targeting in genome. Therefore, the focus of this review is to compare pros and cons of these editing technologies and to elaborate the retrospective scope of gene therapy for β-thalassemia patients.
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Reactive oxygen species responsive nanomotors for gene edited metabolic disruption and immunotherapy.
While gene-editing-based tumor therapy holds promise, conventional passive-diffusion vectors face limited penetration in dense solid tumors. Here, we developed a ROS-driven gene editing nanomotor (RDN@PL), which takes hemin as the core and encapsulates CRISPR/Cas9 plasmids targeting LDHA (A glycolysis key enzyme). In tumor microenvironments, RDN@PL consumes extracellular ROS to fuel self-diffusiophoresis, achieving higher intratumoral accumulation than passive particles. Upon internalization, heme oxygenase-1 (HO-1) degrades RDN@PL, releasing CO and plasmids. LDHA knockout suppresses glycolysis while CO elevates mitochondrial ROS, which triggers apoptosis by disrupting metabolism and enhancing immunity. Simultaneously, extracellular ROS depletion by non-internalized nanomotors reverses immunogenic cell death (ICD) inhibition, enhancing CD8+ T cell infiltration in tumor. The Janus nanomotor enables extracellular ROS scavenging and intracellular ROS increment via HO-1-responsive cargo release and gene editing. This multi-level intervention strategy demonstrates 93.9 % tumor growth suppression in solid tumor models, providing a blueprint for engineering intelligent nanovesicles in precision oncology.
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Effects of concentration of CRISPR/Cas9 components on genetic mosaicism in cytoplasmic microinjected porcine embryos.
Cytoplasmic microinjection (CI) of the CRISPR/Cas9 system enabled the induction of site-specific mutations in porcine zygotes and resulting pigs. However, mosaicism is a serious problem for genetically modified pigs. In the present study, we investigated suitable timing and concentration of CRISPR/Cas9 components for introduction into oocytes/zygotes by CI, to reduce mosaicism in the resulting blastocysts. First, we introduced 20 ng/μl of Cas9 protein and guide RNA (gRNA), targeting the α-1,3-galactosyltransferase (GalT) gene in oocytes before in vitro fertilization (IVF), in zygotes after IVF, or in oocytes/zygotes before and after IVF, twice. CI treatment had no detrimental effects on blastocyst formation rates. The highest value of the rate of mutant blastocysts was observed in zygotes injected after IVF. Next, we injected Cas9 protein and gRNA into zygotes after IVF at a concentration of 20 ng/μl each (20 ng/μl group) or 100 ng/μl each (100 ng/μl group). The ratio of the number of blastocysts that carried mutations to the total number of blastocysts examined in the 100 ng/μl group was significantly higher (P < 0.05) than that in the 20 ng/μl group. Although no blastocysts from the 20 ng/μl group carried a biallelic mutation, 16.7% of blastocysts from the 100 ng/μl group carried a biallelic mutation. In conclusion, increasing the concentration of Cas9 protein and gRNA is effective in generating biallelic mutant blastocysts. To reduce mosaicism, however, further optimization of the timing of CI, and the concentration of CRISPR/Cas9 components, is needed.
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Controlling Citrate Synthase Expression by CRISPR/Cas9 Genome Editing for n-Butanol Production in Escherichia coli.
Genome editing using CRISPR/Cas9 was successfully demonstrated in Esherichia coli to effectively produce n-butanol in a defined medium under microaerobic condition. The butanol synthetic pathway genes including those encoding oxygen-tolerant alcohol dehydrogenase were overexpressed in metabolically engineered E. coli, resulting in 0.82 g/L butanol production. To increase butanol production, carbon flux from acetyl-CoA to citric acid cycle should be redirected to acetoacetyl-CoA. For this purpose, the 5'-untranslated region sequence of gltA encoding citrate synthase was designed using an expression prediction program, UTR designer, and modified using the CRISPR/Cas9 genome editing method to reduce its expression level. E. coli strains with decreased citrate synthase expression produced more butanol and the citrate synthase activity was correlated with butanol production. These results demonstrate that redistributing carbon flux using genome editing is an efficient engineering tool for metabolite overproduction.
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Metal coordination micelles for anti-cancer treatment by gene-editing and phototherapy.
CRISPR-Cas9 is a central focus of the emerging field of gene editing and photodynamic therapy (PDT) is a clinical-stage ablation modality combining photosensitizers with light irradiation. But metal coordination biomaterials for the applications of both have rarely been investigated. Herein, Chlorin-e6 (Ce6) Manganese (Mn) coordination micelles loaded with Cas9, termed Ce6-Mn-Cas9, were developed for augmented combination anti-cancer treatment. Manganese played multiple roles to facilitate Cas9 and single guide RNA (sgRNA) ribonucleoprotein (RNP) delivery, Fenton-like effect, and enhanced endonuclease activity of RNP. Histidine (His)-tagged RNP could be coordinated to Ce6 encapsulated in Pluronic F127 (F127) micelles by simple admixture. Triggered by ATP and endolysosomal acidic pH, Ce6-Mn-Cas9 released Cas9 without altering protein structure or function. Dual guide RNAs were designed to target the antioxidant regulator MTH1 and the DNA repair protein APE1, resulting in increased oxygen and enhanced PDT effect. In a murine tumor model, Ce6-Mn-Cas9 inhibited tumor growth with the combination therapy of PDT and gene editing. Taken together, Ce6-Mn-Cas9 represents a new biomaterial with a high degree of versatility to enable photo- and gene-therapy approaches.
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Dynamically covalent lipid nanoparticles mediate CRISPR-Cas9 genome editing against choroidal neovascularization in mice.
As an important modality for choroidal neovascularization (CNV) treatment, intravitreal injection of vascular endothelial growth factor A (VEGFA) inhibitors suffers from undesired response rate, low patient compliance, and ocular damage. Here, dynamically covalent lipid nanoparticles (LNPs) were engineered to mediate VEGFA gene editing and CNV treatment by codelivering Cas9 mRNA (mCas9) and single guide RNA (sgRNA) targeting VEGFA (sgVEGFA). A library of lipidoids bearing iminoboronate ester linkage was developed via facile "one-pot" synthesis, and the top-performing lipidoid-A4B3C7 was formulated into LNP-A4B3C7 with the highest mRNA transfection efficiency. Inside the diseased retinal pigment epithelial cells, LNPs were dissociated upon H2O2-triggered lipidoid degradation, facilitating mRNA/sgRNA release to potentiate the gene editing efficiency. In laser-induced CNV mice, mCas9/sgVEGFA@LNP-A4B3C7 after single intravitreal injection led to pronounced VEGFA disruption and CNV area reduction, outperforming the clinical anti-VEGF drug in eliciting sustained therapeutic effect. This study establishes a robust nonviral platform for mRNA delivery and genome editing and renders a promising strategy for CNV treatment.
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