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Assessment and Mitigation of CRISPR-Cas9-Induced Nontargeted Translocations.
The performance of CRISPR-mediated genome editing near inverted repeats (IRs) potentially results in chromosomal translocations and other catastrophic rearrangements. However, the extent of this risk may be significantly underestimated because current reporter systems focus solely on site-specific translocations. Here, trans-acting reporter systems in Escherichia coli are developed to detect nontargeted translocations. Markedly increased frequency of translocations following CRISPR-Cas9 activation is observed, with the magnitude determined primarily by the length of the IRs and the proximity between Cas9 target sites and IRs. These translocations arise through a combination of intramolecular single-strand annealing and alternative end-joining mechanisms. Furthermore, it is discovered that introducing segments homologous to IR loci can substantially mitigate nontargeted translocations without significantly compromising CRISPR-Cas9-mediated editing. The study provides valuable insights into the genetic risks associated with CRISPR technologies and suggests a viable strategy for developing genetically safer CRISPR systems.
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Generation of a FRMD5 knockout human embryonic stem cell line by CRISPR/Cas9 editing.
FRMD5 is a protein-coding gene on human chromosome 15q15.3 encoding a FERM domain-containing protein. Its mutations are linked to NEDEMA, a rare autosomal dominant neurodevelopmental disorder characterized by developmental delay, intellectual disability, ataxia, epilepsy, and eye movement abnormalities (Keller Sarmiento et al., 2024).We established a FRMD5 knockout (FRMD5-/-) human embryonic stem cell line via CRISPR/Cas9. This line shows normal karyotype, expresses pluripotency markers, and differentiates into three germ layers, serving as a valuable tool for studying FRMD5 in neural development.
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Generation of a homozygous ARHGAP11B knockout hiPSC line by CRISPR/Cas9 system.
The human specific gene ARHGAP11B is preferentially expressed in neural progenitors of fetal neocortex and plays a key role in the evolutionary expansion of the neocortex. Here, we generated a homozygous ARHGAP11B knockout human induced pluripotent stem cell (hiPSC) line through CRISPR/Cas9 gene editing system. ARHGAP11B deficient cell line maintained a normal karyotype (46, XX), expressed pluripotency markers, and showed the capability to spontaneously differentiate into all three germ layers in vivo. The ARHGAP11B knockout cell line can provide a new cell model for studying the evolution of human neocortex.
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CRISPR/CAS9 mutagenesis of a single r-opsin gene blocks phototaxis in a marine larva.
Many marine animals depend upon a larval phase of their life cycle to locate suitable habitat, and larvae use light detection to influence swimming behaviour and dispersal. Light detection is mediated by the opsin genes, which encode light-sensitive transmembrane proteins. Previous studies suggest that r-opsins in the eyes mediate locomotory behaviour in marine protostomes, but few have provided direct evidence through gene mutagenesis. Larvae of the marine annelid Capitella teleta have simple eyespots and are positively phototactic, although the molecular components that mediate this behaviour are unknown. Here, we characterize the spatio-temporal expression of the rhabdomeric opsin genes in C. teleta and show that a single rhabdomeric opsin gene, Ct-r-opsin1, is expressed in the larval photoreceptor cells. To investigate its function, Ct-r-opsin1 was disrupted using CRISPR/CAS9 mutagenesis. Polymerase chain reaction amplification and DNA sequencing demonstrated efficient editing of the Ct-r-opsin1 locus. In addition, the pattern of Ct-r-opsin1 expression in photoreceptor cells was altered. Notably, there was a significant decrease in larval phototaxis, although the eyespot photoreceptor cell and associated pigment cell formed normally and persisted in Ct-r-opsin1-mutant animals. The loss of phototaxis owing to mutations in Ct-r-opsin1 is similar to that observed when the entire photoreceptor and pigment cell are deleted, demonstrating that a single r-opsin gene is sufficient to mediate phototaxis in C. teleta. These results establish the feasibility of gene editing in animals like C. teleta, and extend previous work on the development, evolution and function of the C. teleta visual system . Our study represents one example of disruption of animal behaviour by gene editing through CRISPR/CAS9 mutagenesis, and has broad implications for performing genome editing studies in a wide variety of other understudied animals.
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Direct Pathway Synthesis and Editing (DiPaSE): A One-Pot DNA Assembly Method for Accurate and Efficient Refactoring of High-GC Biosynthetic Gene Clusters.
Natural products (NPs) produced by actinobacteria, particularly Streptomyces species, represent a rich source of bioactive compounds and have yielded many clinically important compounds. Actinobacterial genomes are characterized by high GC content and typically harbor 20-40 biosynthetic gene clusters (BGCs) per genome, which encode diverse NPs such as polyketides, peptides, and glycosides. CRISPR/Cas-based genome editing has emerged as a promising tool to activate silent BGCs and engineer NP biosynthesis. However, the efficiency of multiplex editing drastically decreases as the number of targeted sites increases. Here, we report a novel one-pot DNA assembly method, termed direct pathway synthesis and editing (DiPaSE), for the efficient synthesis and multiplex editing of long, high-GC BGCs. DiPaSE accurately assembles multiple high-GC DNA fragments up to 60 kb and enables simultaneous deletions and insertions within a target BGC without compromising the assembly efficiency. Using this approach, we identified functions of previously uncharacterized genes in the aureothin BGC and significantly enhanced the titer of the corresponding NP. The workflow employs conventional polymerase chain reaction, type IIP restriction enzymes, commercially available DNA assembly reagents, and Escherichia coli, providing a simple, cost-effective, and broadly applicable platform for genome mining, BGC refactoring, and rational design of artificial biosynthetic pathways.
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Application of CRISPR/Cas9 for GDF9 Gene Editing in Caprine Granulosa Cells: Effects on Receptor Signalling and FGF2 Response.
Fecundity-related genes, such as GDF9, play a critical role in regulating ovulation, fertilisation and early embryonic development. This study aimed to elucidate the functional role of GDF9 in caprine granulosa cells by employing CRISPR/Cas9-mediated gene editing. The CRISPR/Cas9 system, incorporating single guide RNA (sgRNA) and Cas9 endonuclease, was used to specifically disrupt the GDF9 gene. Successful GDF9 knockout was confirmed via the T7 Endonuclease I (T7E1) cleavage assay. Subsequent analyses assessed the impact of GDF9 disruption on the expression of GDF9 and its associated receptors-BMPR-1A, BMPR-1B and BMPR-II. Additionally, the study examined the modulatory effects of fibroblast growth factor 2 (FGF2) on receptor expression. FGF2 treatment led to increased mRNA expression of BMPR-1A, BMPR-1B and BMPR-II in wild-type granulosa cells. Furthermore, follicle-stimulating hormone receptor (FSHR) levels were significantly upregulated, whereas luteinising hormone receptor (LHR) expression decreased following FGF2 stimulation in wild-type cells. In contrast, GDF9-knockout cells showed elevated expression of both FSHR and LHR. The study also investigated the impact of GDF9 deletion on the expression of key steroidogenic genes, particularly StAR. The combined presence of GDF9 and FGF2 synergistically enhanced StAR expression. Cellular responses to FGF2 included a downregulation of CASPASE 3, indicating reduced apoptosis and an upregulation of PCNA, suggesting increased cell proliferation. In conclusion, this study provides novel insights into the regulatory role of GDF9 in ovarian granulosa cell function and highlights the utility of CRISPR/Cas9 technology for functional genomics in caprine species. The findings have significant implications for enhancing reproductive performance through targeted gene modulation.
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Bacterial Genome Editing Strategy for Control of Transcription and Protein Stability.
In molecular biology and cell factory engineering, tools that enable control of protein production and stability are highly important. Here, we describe protocols for tagging genes in Escherichia coli allowing for inducible degradation and transcriptional control of any soluble protein of interest. The underlying molecular biology is based on the two cross-kingdom tools CRISPRi and the N-end rule for protein degradation. Genome editing is performed with the CRMAGE technology and randomization of the translational initiation region minimizes the polar effects of tag insertion. The approach has previously been applied for targeting proteins originating from essential operon-located genes and has potential to serve as a universal synthetic biology tool.
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Cas9 degradation in human cells using phage anti-CRISPR proteins.
Bacteriophages encode anti-CRISPR (Acr) proteins that inactivate CRISPR-Cas bacterial immune systems, allowing successful invasion, replication, and prophage integration. Acr proteins inhibit CRISPR-Cas systems using a wide variety of mechanisms. AcrIIA1 is encoded by numerous phages and plasmids, binds specifically to the Cas9 HNH domain, and was the first Acr discovered to inhibit SpyCas9. Here, we report the observation of AcrIIA1-induced degradation of SpyCas9 and SauCas9 in human cell culture, the first example of Acr-induced degradation of CRISPR-Cas nucleases in human cells. AcrIIA1-induced degradation of SpyCas9 is abolished by mutations in AcrIIA1 that break a direct physical interaction between the 2 proteins. Targeted Cas9 protein degradation by AcrIIA1 could modulate Cas9 nuclease activity in human therapies. The small size and specificity of AcrIIA1 could be used in a CRISPR-Cas proteolysis-targeting chimera (PROTAC), providing a tool for developing safe and precise gene editing applications.
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Adenoviral vectors encoding CRISPR/Cas9 multiplexes rescue dystrophin synthesis in unselected populations of DMD muscle cells.
Mutations disrupting the reading frame of the ~2.4 Mb dystrophin-encoding DMD gene cause a fatal X-linked muscle-wasting disorder called Duchenne muscular dystrophy (DMD). Genome editing based on paired RNA-guided nucleases (RGNs) from CRISPR/Cas9 systems has been proposed for permanently repairing faulty DMD loci. However, such multiplexing strategies require the development and testing of delivery systems capable of introducing the various gene editing tools into target cells. Here, we investigated the suitability of adenoviral vectors (AdVs) for multiplexed DMD editing by packaging in single vector particles expression units encoding the Streptococcus pyogenes Cas9 nuclease and sequence-specific gRNA pairs. These RGN components were customized to trigger short- and long-range intragenic DMD excisions encompassing reading frame-disrupting exons in patient-derived muscle progenitor cells. By allowing synchronous and stoichiometric expression of the various RGN components, we demonstrate that dual RGN-encoding AdVs can correct over 10% of target DMD alleles, readily leading to the detection of Becker-like dystrophin proteins in unselected muscle cell populations. Moreover, we report that AdV-based gene editing can be tailored for removing mutations located within the over 500-kb major DMD mutational hotspot. Hence, this single DMD editing strategy can in principle tackle a broad spectrum of mutations present in more than 60% of patients with DMD.
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CRISPR editing as a therapeutic strategy for Duchenne muscular dystrophy-anti-Cas9 immune response casts its shadow over safety and efficacy.
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