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Cellular function reinstitution of offspring red blood cells cloned from the sickle cell disease patient blood post CRISPR genome editing.
BACKGROUND: Sickle cell disease (SCD) is a disorder of red blood cells (RBCs) expressing abnormal hemoglobin-S (HbS) due to genetic inheritance of homologous HbS gene. However, people with the sickle cell trait (SCT) carry a single allele of HbS and do not usually suffer from SCD symptoms, thus providing a rationale to treat SCD. METHODS: To validate gene therapy potential, hematopoietic stem cells were isolated from the SCD patient blood and treated with CRISPR/Cas9 approach. To precisely dissect genome-editing effects, erythroid progenitor cells were cloned from single colonies of CRISPR-treated cells and then expanded for simultaneous gene, protein, and cellular function studies. RESULTS: Genotyping and sequencing analysis revealed that the genome-edited erythroid progenitor colonies were converted to SCT genotype from SCD genotype. HPLC protein assays confirmed reinstallation of normal hemoglobin at a similar level with HbS in the cloned genome-edited erythroid progenitor cells. For cell function evaluation, in vitro RBC differentiation of the cloned erythroid progenitor cells was induced. As expected, cell sickling assays indicated function reinstitution of the genome-edited offspring SCD RBCs, which became more resistant to sickling under hypoxia condition. CONCLUSIONS: This study is an exploration of genome editing of SCD HSPCs.
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Accelerated genome engineering of Pseudomonas putida by I-SceI-mediated recombination and CRISPR-Cas9 counterselection.
Pseudomonas species have become reliable platforms for bioproduction due to their capability to tolerate harsh conditions imposed by large-scale bioprocesses and their remarkable resistance to diverse physicochemical stresses. The last few years have brought forth a variety of synthetic biology tools for the genetic manipulation of pseudomonads, but most of them are either applicable only to obtain certain types of mutations, lack efficiency, or are not easily accessible to be used in different Pseudomonas species (e.g. natural isolates). In this work, we describe a versatile, robust and user-friendly procedure that facilitates virtually any kind of genomic manipulation in Pseudomonas species in 3-5 days. The protocol presented here is based on DNA recombination forced by double-stranded DNA cuts (through the activity of the I-SceI homing meganuclease from yeast) followed by highly efficient counterselection of mutants (aided by a synthetic CRISPR-Cas9 device). The individual parts of the genome engineering toolbox, tailored for knocking genes in and out, have been standardized to enable portability and easy exchange of functional gene modules as needed. The applicability of the procedure is illustrated both by eliminating selected genomic regions in the platform strain P. putida KT2440 (including difficult-to-delete genes) and by integrating different reporter genes (comprising novel variants of fluorescent proteins) into a defined landing site in the target chromosome.
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Streamlined ex vivo and in vivo genome editing in mouse embryos using recombinant adeno-associated viruses.
Recent advances using CRISPR-Cas9 approaches have dramatically enhanced the ease for genetic manipulation in rodents. Notwithstanding, the methods to deliver nucleic acids into pre-implantation embryos have hardly changed since the original description of mouse transgenesis more than 30 years ago. Here we report a novel strategy to generate genetically modified mice by transduction of CRISPR-Cas9 components into pre-implantation mouse embryos via recombinant adeno-associated viruses (rAAVs). Using this approach, we efficiently generated a variety of targeted mutations in explanted embryos, including indel events produced by non-homologous end joining and tailored mutations using homology-directed repair. We also achieved gene modification in vivo by direct delivery of rAAV particles into the oviduct of pregnant females. Our approach greatly simplifies the generation of genetically modified mice and, more importantly, opens the door for streamlined gene editing in other mammalian species.
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Rewiring miR-22/SNAI1 via CRISPR-based edge editing destabilizes the epithelial phenotype.
Epithelial-to-Mesenchymal Transition (EMT) is a critical biological process by which cells acquire enhanced migratory and invasive properties. A key signaling pathway involved in EMT phenotypes includes transforming growth factor β (TGFβ) and transcription factors (TFs) such as SNAIL, ZEB, and TWIST. Additionally, microRNAs (miRNAs) - small, non-coding molecules that regulate gene expression by targeting mRNA transcripts - directly regulate genes central to the EMT process. Notably, miR-22 has been identified as a significant regulator of EMT through direct inhibition of EMT drivers like SNAI1 and indirect regulation of upstream genes. In this study, we performed CRISPR-based network rewiring by selectively removing an edge-the connection between two nodes-to investigate its impact on EMT dynamics. Specifically, we disrupted the connection between miR-22 and SNAI1 without affecting other interactions involving miR-22 or SNAI1 and examined the resulting effects on EMT. We demonstrate that the removal of the miR-22 target site from the SNAI1 gene renders cells more sensitive to TGFβ-mediated EMT. This finding highlights the unique advantage of edge-specific perturbation by ablating the direct regulatory connection between miR-22 and SNAI1. We demonstrate that all measured downstream effects on EMT can be attributed to this single interaction, independent of miR-22's influence on other targets or indirect pathways. More generally, our results underscore the importance of CRISPR-mediated edge ablation for exploring the interactions that govern biological networks and highlight an underexplored opportunity to develop edge-based therapeutic modalities.
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Targeted in vivo knock-in of human alpha-1-antitrypsin cDNA using adenoviral delivery of CRISPR/Cas9.
Serum deficiency diseases such as alpha-1-antitrypsin deficiency are characterized by reduced function of serum proteins, caused by deleterious genetic mutations. These diseases are promising targets for genetic interventions. Gene therapies using viral vectors have been used to introduce correct copies of the disease-causing gene in preclinical and clinical studies. However, these studies highlighted that disease-alleviating gene expression is lost over time. Integration into a specific chromosomal site could provide lasting therapeutic expression to overcome this major limitation. Additionally, targeted integration could avoid detrimental mutagenesis associated with integrative vectors, such as tumorigenesis or functional gene perturbation. To test if adenoviral vectors can facilitate long-term gene expression through targeted integration, we somatically incorporated the human alpha-1-antitrypsin gene into the ROSA26 "safe harbor" locus in murine livers, using CRISPR/Cas9. We found adenoviral-mediated delivery of CRISPR/Cas9 achieved gene editing outcomes persisting over 200 days. Furthermore, gene knock-in maintained greater levels of the serum protein than provided by episomal expression. Importantly, our "knock-in" approach is generalizable to other serum proteins and supports in vivo cDNA replacement therapy to achieve stable gene expression.
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CRISPR in clinical oncology: translational advances from molecular diagnostics to therapeutics.
Cancer care is increasingly driven by molecular classification, yet many key oncogenic drivers remain undruggable, and intrinsic or acquired resistance to treatment frequently limits durable clinical benefit. CRISPR-Cas technologies provide a modular, programmable platform to interrogate and directly manipulate cancer biology via sequence-specific targeting of DNA or RNA and have advanced from experimental tools to the early stages of clinical translation. In this Review, we outline how CRISPR-enabled functional genomics approaches can reveal unexpected cancer dependencies and resistance mechanisms. We discuss emerging applications of CRISPR-based diagnostics in oncology that convert precise nucleic acid sequence recognition into rapid mutation detection. We also discuss applications of CRISPR in therapeutic strategies ranging from ex vivo immune cell engineering to nascent in vivo interventions that directly target tumour-related sequences such as fusion junctions or single-nucleotide variants. Finally, we highlight technological and regulatory challenges, including effective delivery of the editing machinery to cells in vivo, safety and platform-level regulatory frameworks, that will determine the clinical utility of CRISPR-based diagnostics and therapies in oncology.
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Application of CRISPR genetic screens to investigate neurological diseases.
The adoption of CRISPR-Cas9 technology for functional genetic screens has been a transformative advance. Due to its modular nature, this technology can be customized to address a myriad of questions. To date, pooled, genome-scale studies have uncovered genes responsible for survival, proliferation, drug resistance, viral susceptibility, and many other functions. The technology has even been applied to the functional interrogation of the non-coding genome. However, applications of this technology to neurological diseases remain scarce. This shortfall motivated the assembly of a review that will hopefully help researchers moving in this direction find their footing. The emphasis here will be on design considerations and concepts underlying this methodology. We will highlight groundbreaking studies in the CRISPR-Cas9 functional genetics field and discuss strengths and limitations of this technology for neurological disease applications. Finally, we will provide practical guidance on navigating the many choices that need to be made when implementing a CRISPR-Cas9 functional genetic screen for the study of neurological diseases.
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Cas4 Nucleases Define the PAM, Length, and Orientation of DNA Fragments Integrated at CRISPR Loci.
To achieve adaptive and heritable immunity against viruses and other mobile genetic elements, CRISPR-Cas systems must capture and store short DNA fragments (spacers) from these foreign elements into host genomic CRISPR arrays. This process is catalyzed by conserved Cas1/Cas2 integration complexes, but the specific roles of another highly conserved protein linked to spacer acquisition, the Cas4 nuclease, are just now emerging. Here, we show that two Cas4 nucleases (Cas4-1 and Cas4-2) play critical roles in CRISPR spacer acquisition in Pyrococcus furiosus. The nuclease activities of both Cas4 proteins are required to process protospacers to the correct size. Cas4-1 specifies the upstream PAM (protospacer adjacent motif), while Cas4-2 specifies the conserved downstream motif. Both Cas4 proteins ensure CRISPR spacer integration in a defined orientation leading to CRISPR immunity. Collectively, these findings provide in vivo evidence for critical roles of Cas4 nucleases in protospacer generation and functional spacer integration at CRISPR arrays.
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CRISPR-Cas10 assisted editing of virulent staphylococcal phages.
Phages are the most abundant entities in the biosphere and profoundly impact the bacterial populations within and around us. They attach to a specific host, inject their DNA, hijack the host's cellular processes, and replicate exponentially while destroying the host. Historically, phages have been exploited as powerful antimicrobials, and phage-derived proteins have constituted the basis for numerous biotechnological applications. Only in recent years have metagenomic studies revealed that phage genomes harbor a rich reservoir of genetic diversity, which might afford further therapeutic and/or biotechnological value. Nevertheless, functions for the majority of phage genes remain unknown, and due to their swift and destructive replication cycle, many phages are intractable by current genetic engineering techniques. Whether to advance the basic understanding of phage biology or to tap into their potential applications, efficient methods for phage genetic engineering are needed. Recent reports have shown that CRISPR-Cas systems, a class of prokaryotic immune systems that protect against phage infection, can be harnessed to engineer diverse phages. In this chapter, we describe methods to genetically manipulate virulent phages using CRISPR-Cas10, a Type III-A CRISPR-Cas system native to Staphylococcus epidermidis. A method for engineering phages that infect a CRISPR-less Staphylococcus aureus host is also described. Both approaches have proved successful in isolating desired phage mutants with 100% efficiency, demonstrating that CRISPR-Cas10 constitutes a powerful tool for phage genetic engineering. The relatively widespread presence of Type III CRISPR-Cas systems in bacteria and archaea imply that similar strategies may be used to manipulate the genomes of diverse prokaryotic viruses.
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Synthesizing AND gate minigene circuits based on CRISPReader for identification of bladder cancer cells.
The logical AND gate gene circuit based on the CRISPR-Cas9 system can distinguish bladder cancer cells from normal bladder epithelial cells. However, the layered artificial gene circuits have the problems of high complexity, difficulty in accurately predicting the behavior, and excessive redundancy, which cannot be applied to clinical translation. Here, we construct minigene circuits based on the CRISPReader, a technology used to control promoter-less gene expression in a robust manner. The minigene circuits significantly induce robust gene expression output in bladder cancer cells, but have nearly undetectable gene expression in normal bladder epithelial cells. The minigene circuits show a higher capability for cancer identification and intervention when compared with traditional gene circuits, and could be used for in vivo cancer gene therapy using the all-in-one AAV vector. This approach expands the design ideas and concepts of gene circuits in medical synthetic biology.
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