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Possible Reversion of CRISPR-Cas9-Edited Sequences in Octoploid Strawberry.
Gene editing is more challenging in octoploids due to the presence of multiple copies of each gene. However, the ability to edit genes in these plants would allow editing in commercial varieties. Here, we delivered sequences targeting FaMYB9 into octoploid strawberry "Honeoye" and identified several gene-edited lines. Among them, the heterozygous gene-edited line FaMYB9CR-15 had curved and wrinkled leaves at 3 months, whereas leaves of 3-month-old wild-type (WT) strawberry seedlings were elliptical with a smooth surface. At that stage, FaMYB9CR-15 leaves also had large patches of wax. We identified 11,402 differentially expressed genes, divided into four clusters, between WT and FaMYB9CR-15 seedlings at 3 months. Notably, cluster 4 genes-related to nonhomologous end joining, microhomology-mediated end joining repairs, homologous recombination, nucleotide excision repair, and mismatch repair-were more highly expressed in the gene-edited line than in the WT. Surprisingly, by 6 months of age, FaMYB9CR-15 leaves had become smooth with small patches of wax, and expression levels of cluster 4 genes were significantly lower than at 3 months. Over the same period, the percentage of FaMYB9 loci harboring the mutant allele decreased from 70.2% to 43.7%. These findings lead us to conclude that there could be reversion of mutated sequences in octoploid strawberry, emphasizing the challenges of gene editing high-ploidy materials.
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Functional Genomics for Cancer Drug Target Discovery.
Functional genomics describes a field of biology that uses a range of approaches for assessing gene function with high-throughput molecular, genetic, and cellular technologies. The near limitless potential for applying these concepts to study the activities of all genetic loci has completely upended how today's cancer biologists tackle drug target discovery. We provide an overview of contemporary functional genomics platforms, highlighting areas of distinction and complementarity across technologies, so as to aid in the development or interpretation of cancer-focused screening efforts.
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Control of gene editing by manipulation of DNA repair mechanisms.
DNA double-strand breaks (DSBs) are produced intentionally by RNA-guided nucleases to achieve genome editing through DSB repair. These breaks are repaired by one of two main repair pathways, classic non-homologous end joining (c-NHEJ) and homology-directed repair (HDR), the latter being restricted to the S/G2 phases of the cell cycle and notably less frequent. Precise genome editing applications rely on HDR, with the abundant c-NHEJ formed mutations presenting a barrier to achieving high rates of precise sequence modifications. Here, we give an overview of HDR- and c-NHEJ-mediated DSB repair in gene editing and summarize the current efforts to promote HDR over c-NHEJ.
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Immunometabolic reprogramming of macrophages with inhalable CRISPR/Cas9 nanotherapeutics for acute lung injury intervention.
Acute lung injury (ALI) represents a critical respiratory condition typified by rapid-onset lung inflammation, contributing to elevated morbidity and mortality rates. Central to ALI pathogenesis lies macrophage dysfunction, characterized by an overabundance of pro-inflammatory cytokines and a shift in metabolic activity towards glycolysis. This study emphasizes the crucial function of glucose metabolism in immune cell function under inflammatory conditions and identifies hexokinase 2 (HK2) as a key regulator of macrophage metabolism and inflammation. Given the limitations of HK2 inhibitors, we propose the CRISPR/Cas9 system for precise HK2 downregulation. We developed an aerosolized core-shell liposomal nanoplatform (CSNs) complexed with CaP for efficient drug loading, targeting lung macrophages. Various CSNs were synthesized to encapsulate an mRNA based CRISPR/Cas9 system (mCas9/gHK2), and their gene editing efficiency and HK2 knockout were examined at both gene and protein levels in vitro and in vivo. The CSN-mCas9/gHK2 treatment demonstrated a significant reduction in glycolysis and inflammation in macrophages. In an LPS-induced ALI mouse model, inhaled CSN-mCas9/gHK2 mitigated the proinflammatory tumor microenvironment and reprogrammed glucose metabolism in the lung, suggesting a promising strategy for ALI prevention and treatment. This study highlights the potential of combining CRISPR/Cas9 gene editing with inhalation delivery systems for effective, localized pulmonary disease treatment, underscoring the importance of targeted gene modulation and metabolic reprogramming in managing ALI. STATEMENT OF SIGNIFICANCE: This study investigates an inhalable CRISPR/Cas9 gene editing system targeting pulmonary macrophages, with the aim of modulating glucose metabolism to alleviate Acute Lung Injury (ALI). The research highlights the role of immune cell metabolism in inflammation, as evidenced by changes in macrophage glucose metabolism and a notable reduction in pulmonary edema and inflammation. Additionally, observed alterations in macrophage polarization and cytokine levels in bronchoalveolar lavage fluid suggest potential therapeutic implications. These findings not only offer insights into possible ALI treatments but also contribute to the understanding of immune cell metabolism in inflammatory diseases, which could be relevant for various inflammatory and metabolic disorders.
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In silico analysis of potential off-target sites to gene editing for Mucopolysaccharidosis type I using the CRISPR/Cas9 system: Implications for population-specific treatments.
Mucopolysaccharidosis type I (MPS I) is caused by alpha-L-iduronidase deficiency encoded by the IDUA gene. Therapy with CRISPR/Cas9 is being developed for treatment, however a detailed investigation of off-target effects must be performed. This study aims to evaluate possible off-targets for a sgRNA aiming to correct the most common variant found in MPS I patients (p.Trp402*). A total of 272 potential off-target sequences was obtained and 84 polymorphic sites were identified in these sequences with a frequency equal to or greater than 1% in at least one of the populations. In the majority of cases, polymorphic sites decrease the chance of off-target cleavage and a new PAM was created, which indicates the importance of such analysis. This study highlights the importance of screening off-targets in a population-specific context using Mucopolysaccharidosis type I as an example of a problem that concerns all therapeutic treatments. Our results can have broader applications for other targets already clinically in use, as they could affect CRISPR/Cas9 safety and efficiency.
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What we can learn from the first personalized CRISPR-treated baby to tackle genetic brain disorders.
The landmark report on personalized CRISPR genome editing to treat an infant (baby KJ) with a life-threatening liver disease sparked widespread attention,1 ushering in a new era of precision genetic intervention. This piece discusses the key challenges and opportunities in translating this milestone into treatments for genetic brain disorders.
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Development of an in vivo cleavable donor plasmid for targeted transgene integration by CRISPR-Cas9 and CRISPR-Cas12a.
The CRISPR-Cas system is widely used for genome editing of cultured cells and organisms. The discovery of a new single RNA-guided endonuclease, CRISPR-Cas12a, in addition to the conventional CRISPR-Cas9 has broadened the number of editable target sites on the genome. Here, we developed an in vivo cleavable donor plasmid for precise targeted knock-in of external DNA by both Cas9 and Cas12a. This plasmid, named pCriMGET_9-12a (plasmid of synthetic CRISPR-coded RNA target sequence-equipped donor plasmid-mediated gene targeting via Cas9 and Cas12a), comprises the protospacer-adjacent motif sequences of Cas9 and Cas12a at the side of an off-target free synthetic CRISPR-coded RNA target sequence and a multiple cloning site for donor cassette insertion. pCriMGET_9-12a generates a linearized donor cassette in vivo by both CRISPR-Cas9 and CRISPR-Cas12a, which resulted in increased knock-in efficiency in culture cells. This method also achieved > 25% targeted knock-in of long external DNA (> 4 kb) in mice by both CRISPR-Cas9 and CRISPR-Cas12a. The pCriMGET_9-12a system expands the genomic target space for transgene knock-in and provides a versatile, low-cost, and high-performance CRISPR genome editing tool.
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High-Level dCas9 Expression Induces Abnormal Cell Morphology in Escherichia coli.
Along with functional advances in the use of CRISPR/Cas9 for genome editing, endonuclease-deficient Cas9 (dCas9) has provided a versatile molecular tool for exploring gene functions. In principle, differences in cell phenotypes that result from the RNA-guided modulation of transcription levels by dCas9 are critical for inferring with gene function; however, the effect of intracellular dCas9 expression on bacterial morphology has not been systematically elucidated. Here, we observed unexpected morphological changes in Escherichia coli mediated by dCas9, which were then characterized using RNA sequencing (RNA-Seq) and chromatin immunoprecipitation sequencing (ChIP-Seq). Growth rates were severely decreased, to approximately 50% of those of wild type cells, depending on the expression levels of dCas9. Cell shape was changed to abnormal filamentous morphology, indicating that dCas9 affects bacterial cell division. RNA-Seq revealed that 574 genes were differentially transcribed in the presence of high expression levels of dCas9. Genes associated with cell division were upregulated, which was consistent with the observed atypical morphologies. In contrast, 221 genes were downregulated, and these mostly encoded proteins located in the cell membrane. Further, ChIP-Seq results showed that dCas9 directly binds upstream of 37 genes without single-guide RNA, including fimA, which encodes bacterial fimbriae. These results support the fact that dCas9 has critical effects on cell division as well as inner and outer membrane structure. Thus, to precisely understand gene functions using dCas9-driven transcriptional modulation, the regulation of intracellular levels of dCas9 is pivotal to avoid unexpected morphological changes in E. coli.
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Nanopore Electroporation: A New Delivery Method Within the Field of Epigenetic Editing.
Epigenetic modifications influence gene expression and contribute to type 2 diabetes (T2D), but establishing causality requires targeted modulation of specific genes. CRISPR-dCas9-based tools offer this potential, yet β-cells are notoriously difficult to transfect, and efficient, non-viral delivery methods are lacking. Here, we developed nanopore-mediated electroporation to deliver a CRISPR interference (CRISPRi) system to clonal INS1 β-cells, achieving targeted downregulation of insulin expression. Cells were seeded atop a nanopore substrate with CRISPRi plasmids in solution below. Mild electric pulses generated transient nanoscale pores in the membrane, enabling electrophoretic delivery of plasmids into the cytosol while preserving high cell viability. The CRISPRi system comprised the transcriptional repressor Krueppel-associated Box Domain (KRAB) fused to an inactive Cas9 (dCas9), guided to the transcription start site of the insulin-1 gene (Ins1) by a single guide RNA (sgRNA). After transfection, Ins1 expression was significantly reduced, demonstrating effective modulation of gene expression in this difficult-to-transfect cell type. This nanopore electroporation approach provides a robust, safe, and efficient platform for delivering CRISPR-dCas9-based epigenetic editors in pancreatic β-cells. By enabling precise gene regulation, it opens avenues for mechanistic studies of epigenetic contributions to T2D and potentially other challenging cell systems.
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Generation of a new DiCre expressing parasite strain for functional characterization of Plasmodium falciparum genes in blood stages.
Conditional regulation is a highly beneficial system for studying the function of essential genes in Plasmodium falciparum and dimerizable Cre recombinase (DiCre) is a recently adapted conditional regulation system suitable for this purpose. In the DiCre system, two inactive fragments of Cre are reconstituted to form a functionally active enzyme in the presence of rapamycin. Different loci have been targeted to generate parasite lines that express the DiCre enzyme. Here, we have used marker-free CRISPR-Cas9 gene editing to integrate the DiCre cassette in a redundant cg6 locus. We have shown the utility of the newly generated ∆cg6DC4 parasites in mediating robust, rapid, and highly specific excision of exogenously encoded gfp sequence. The ∆cg6DC4 parasites are also capable of conditional excision of an endogenous parasite gene, PF3D7_1246000. Conditional deletion of PF3D7_1246000 did not cause any inhibition in the asexual proliferation of the parasites. Furthermore, the health and morphology of the mutant parasites were comparable to that of the control parasites in Giemsa smears. The availability of another stable DiCre parasite strain competent for conditional excision of target genes will expedite functional characterization and validation of novel drug and vaccine targets against malaria.
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