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Reducing competition between msd and genomic DNA improves retron editing efficiency.

Retrons, found in bacteria and used for defense against phages, generate a unique molecule known as multicopy single-stranded DNA (msDNA). This msDNA mimics Okazaki fragments during DNA replication, making it a promising tool for targeted gene editing in prokaryotes. However, existing retron systems often exhibit suboptimal editing efficiency. Here, we identify the msd gene in Escherichia coli, which encodes the noncoding RNA template for msDNA synthesis and carries the homologous sequence of the target gene to be edited, as a critical bottleneck. Sequence homology causes the msDNA to bind to the msd gene, thereby reducing its efficiency in editing the target gene. To address this issue, we engineer a retron system that tailors msDNA to the leading strand of the plasmid containing the msd gene. This strategy minimizes msd gene editing and reduces competition with target genes, significantly increasing msDNA availability. Our optimized system achieves very high retron editing efficiency, enhancing performance and expanding the potential for in vivo techniques that rely on homologous DNA synthesis.

Gene Editing↗

Spacer-engineered donor DNA enhances CRISPR-Cas9-mediated knockin to establish a chemical knockdown platform for endogenous proteins.

Precise installation of functional protein domains at endogenous loci is a powerful approach for interrogating protein functions, but its broad application is limited by the low efficiency of homology-directed repair (HDR)-mediated knockin during Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 gene editing. Here, we investigated a simple donor DNA engineering strategy that enhances HDR-mediated gene knockin by appending additional gRNA-recognizable spacer sequences to donor templates. Systematic analysis of linear dsDNA and plasmid donors showed that spacer position, length, and orientation influenced HDR efficiency, and that spacer-containing donors improved knockin across multiple genomic loci, insertion sizes, cell types and delivery modalities. Mechanistic analyses revealed that spacer-containing donors formed stable complexes with Cas9/gRNA and showed increased nuclear localization, supporting nuclear delivery as a key contributor to improved editing outcomes. We then applied this gene-editing strategy to establish a chemical knockdown platform by installing drug-responsive degrons at endogenous loci, generating cell lines in which GSK3β or Lin28A protein could be rapidly, potently and reversibly depleted by drug treatment. These platforms enable selective modulation of endogenous proteins and reveal cellular responses that may differ from those obtained using conventional genetic perturbation. Together, this work establishes a readily implementable framework that integrates improved gene editing with on-demand chemical knockdown of endogenous proteins.

CRISPR-Cas9↗

CRISPR-Cas9-induced genetic mosaicism in three species of the microcrustacean Daphnia.

Genetic mosaicism can arise from in vivo CRISPR-Cas9 gene editing, especially in the embryos. This study evaluates the extent of genetic mosaicism resulted from CRISPR-Cas9-mediated knockout for 11 genes in the freshwater microcrustacean Daphnia magna, Daphnia pulex, and Daphnia sinensis. Based on extensive genotyping data of the asexually produced progenies of successfully edited females, we find strong evidence of mosaicism in 9 of these genes. The genotyping data also suggest that the gene editing activity can take place as early as the one-cell embryo stage and extends into the 32-cell and later stages. This study establishes genetic mosaicism as an important feature of Cas9-mediated gene editing in Daphnia.

Animals↗

Stable transmission of targeted gene modification using single-stranded oligonucleotides with flanking LNAs.

Targeted mutagenesis directed by oligonucleotides (ONs) is a promising method for manipulating the genome in higher eukaryotes. In this study, we have compared gene editing by different ONs on two new target sequences, the eBFP and the rd1 mutant photoreceptor betaPDE cDNAs, which were integrated as single copy transgenes at the same genomic site in 293T cells. Interestingly, antisense ONs were superior to sense ONs for one target only, showing that target sequence can by itself impart strand-bias in gene editing. The most efficient ONs were short 25 nt ONs with flanking locked nucleic acids (LNAs), a chemistry that had only been tested for targeted nucleotide mutagenesis in yeast, and 25 nt ONs with phosphorothioate linkages. We showed that LNA-modified ONs mediate dose-dependent target modification and analyzed the importance of LNA position and content. Importantly, when using ONs with flanking LNAs, targeted gene modification was stably transmitted during cell division, which allowed reliable cloning of modified cells, a feature essential for further applications in functional genomics and gene therapy. Finally, we showed that ONs with flanking LNAs aimed at correcting the rd1 stop mutation could promote survival of photoreceptors in retinas of rd1 mutant mice, suggesting that they are also active in vivo.

3',5'-Cyclic-GMP Phosphodiesterases↗

Human apolipoprotein B RNA editing deaminase gene (APOBEC1).

Genomic clones encoding the human APOBEC1 gene and its 5' flanking region have been isolated and characterized. The human gene contains five coding exons. The introns dividing these exons correspond exactly to those found in the mouse gene. The translation initiation site, ATG, is located in exon 2 at the same site as in the mouse. The 5' flanking sequence contains two Alu repeats of the Sq family. Primer extension analysis demonstrated the presence of two major transcription initiation sites. The first transcription initiation site delineates the beginning of a noncoding first exon and resides downstream of the first Alu sequence. The second transcription initiation site is within the second Alu repeat. This Alu repeat resides within the first intron, which is spliced out of the transcript from the first start site. Neither transcription initiation site has a TATA or CCAT box. Comparison with the mouse gene suggests that the Alu sequence insertion split the intestinal promoter and that subsequently the down-stream Alu sequence took on a promoter function. No evidence was found for a far upstream non-tissue-specific promoter similar to that demonstrated in the mouse gene. Rather, consideration of results from the marsupial APOBEC-1 gene suggests that this upstream mouse promoter may have had a later evolutionary origin.

APOBEC-1 Deaminase↗

Towards precision medicine for brain arteriovenous malformations.

Recent advances in cerebrovascular genomics, single-cell biology, pharmacology, and gene editing technology are transforming our understanding of brain arteriovenous malformations (bAVMs) - a leading cause of pediatric hemorrhagic stroke. Once considered static anatomical defects, bAVMs are now recognized as dynamic, genetically driven lesions resulting from somatic mutations in KRAS, BRAF, and pathways involved in arteriovenous specification, angiogenesis, and vascular remodeling. By integrating human genetics, animal models, and endovascular innovations, researchers have uncovered convergent mechanisms that link endothelial Ras/MAPK hyperactivation to abnormal vessel growth and higher rupture risk. These insights provide a foundation for precision medicine approaches that combine molecular diagnostics - such as liquid or endoluminal biopsies - with mutation-specific pharmacotherapies and emerging CRISPR-based gene editing strategies. We suggest that genotype-guided interventions, tailored by spatial and developmental cerebrovascular context, could ultimately reclassify bAVMs from surgically incurable malformations to treatable molecular conditions.

Humans↗

Oogenesis and germinal bed morphology of the brown anole (A. sagrei).

BACKGROUND: The brown anole is a model species of the genus Anolis, a squamate (encompassing lizards and snakes) group widely studied in evolutionary, behavioral, and developmental biology. Full genome annotation, the establishment of gene editing techniques, and comprehensive description of reproductive tract morphology and embryogenesis in this species, has laid the foundation for functional studies. However, analysis of brown anole oogenesis is still required and vital to optimize genome modification, mutant line establishment, and analyses of the evolution of reproductive developmental mechanisms. RESULTS: Here, we characterize ovary morphology and gametogenesis in the female brown anole, A. sagrei using brightfield imaging, microCT, histology staining, electron microscopy, and confocal imaging. We define 10 stages of oocyte maturation which commences inside the oogonial nest within the germinal bed and concludes with the mature follicle ready to ovulate based on follicle size, yolk-acquisition, and follicular, cellular, and basement membrane architecture. CONCLUSIONS: We describe the complete oogenesis of the brown anole in 10 stages and report that oogenesis is highly conserved within iguanids, a suborder of lizards. With our staging framework, we lay the foundation for functional studies of oogenesis and optimized gene-editing.

Journal Article↗

Generation of isogenic gene-corrected cell lines from a USH2A-RP patient-derived iPS cell line.

Comparative studies using induced pluripotent stem cells (iPSCs) from patients with those from healthy individuals as controls are flawed by genetic background contribution to disease phenotype. Here, we used precise gene editing to generate gene-corrected isogenic control lines for a single pathogenic variant in the USH2A gene (c.2276G > T) associated with retinitis pigmentosa (RP). Both homozygously and heterozygously corrected cell lines were successfully generated. These cell lines will serve to unravel RP phenotype differences specific to the USH2A mutation upon their conversion into disease relevant cell types.

Journal Article↗

Delivery of genome editors with engineered virus-like particles.

Genome editing technologies have revolutionized biomedical sciences and biotechnology. However, their delivery in vivo remains one of the major obstacles for clinical translation. Here, we introduce various emerging genome editing systems and review different delivery systems have been developed to realize the promise of in vivo gene editing therapies. In particular, we focus on virus-like particles (VLPs), an emerging delivery platform and provide in depth analysis on recent advancements to improve VLPs delivery potential and highlight opportunities for future improvements. To this end, we also provide detail workflows for engineered VLP (eVLP) selection, production, and purification, along with methods for characterization and validation.

Gene Editing↗

Design of highly functional genome editors by modelling CRISPR-Cas sequences.

Gene editing has the potential to solve fundamental challenges in agriculture, biotechnology and human health. CRISPR-based gene editors derived from microorganisms, although powerful, often show notable functional tradeoffs when ported into non-native environments, such as human cells1. Artificial-intelligence-enabled design provides a powerful alternative with the potential to bypass evolutionary constraints and generate editors with optimal properties. Here, using large language models2 trained on biological diversity at scale, we demonstrate successful precision editing of the human genome with a programmable gene editor designed with artificial intelligence. To achieve this goal, we curated a dataset of more than 1 million CRISPR operons through systematic mining of 26 terabases of assembled genomes and metagenomes. We demonstrate the capacity of our models by generating 4.8× the number of protein clusters across CRISPR-Cas families found in nature and tailoring single-guide RNA sequences for Cas9-like effector proteins. Several of the generated gene editors show comparable or improved activity and specificity relative to SpCas9, the prototypical gene editing effector, while being 400 mutations away in sequence. Finally, we demonstrate that an artificial-intelligence-generated gene editor, denoted as OpenCRISPR-1, exhibits compatibility with base editing. We release OpenCRISPR-1 to facilitate broad, ethical use across research and commercial applications.

CRISPR-Cas Systems↗

Microbe Profile: Streptomyces formicae KY5: an ANT-ibiotic factory.

Streptomyces formicae KY5 was isolated from a Tetraponera penzigi plant-ant nest. It is primarily known for its production of the formicamycins, antibiotics with potent activity against Gram-positive pathogens including methicillin-resistant Staphylococcus aureus, and additionally produces an antifungal compound that inhibits multi-drug-resistant fungal pathogens including Lomentospora prolificans. S. formicae is genetically tractable using CRISPR-Cas9 gene editing, allowing for detailed analysis of the formicamycin biosynthetic gene cluster. AntiSMASH analysis predicts the genome to encode at least 45 secondary metabolite biosynthetic gene clusters, many of which appear to encode novel compounds. Current research efforts are focussing on characterising the regulation of secondary metabolism at a global level in order to switch on pathways that are not typically expressed under standard laboratory conditions with the aim of identifying novel antimicrobials.

Streptomyces↗

Validation of caprine H11 and the Rosa26 platform for transgene integration via CRISPR-based system: investigations on stable transgene expression and genetic biosafety.

CRISPR/Cas9 technology is an efficient tool for site-specific livestock gene editing. However, to minimize potential disruption of host genome function, exogenous genes should be integrated into well-characterized genomic loci, such as H11 or Rosa26, which have been empirically validated for stable transgene expression. This study established a multi-dimensional assessment system to evaluate the biological applicability of the H11 locus and the widely used Rosa26 targeting platform as sites for targeted integration of exogenous genes in goats. Donor cells carrying the enhanced green fluorescent protein (EGFP) reporter gene at the H11 and Rosa26 loci were generated via CRISPR/Cas9-mediated homology-directed repair; this was followed by somatic cell nuclear transfer to produce transgenic cloned embryos and healthy offspring. Multi-dimensional analyses revealed the following. At the cellular level, there was stable and efficient EGFP expression at integration sites, with donor cells maintaining normal cell cycle progression, proliferation capacity, and apoptosis levels, and with no alterations in the transcriptional integrity of adjacent genes. At the embryonic level, there was sustained EGFP expression across pre-implantation embryonic stages, with developmental metrics statistically indistinguishable from wild-type embryos. Finally, at the individual level, cloned offspring exhibited growth phenotypes consistent with wild-type counterparts, and EGFP showed broad-spectrum expression in eight tissues. This study establishes the first CRISPR/Cas9-based crossscale (cellular-embryonic-individual) validation in goats, demonstrating that the H11 and Rosa26 loci support efficient and stable transgene integration in goats. These results provide a precise and predictable technical framework for livestock genetic improvement.

Animals↗

Patterns of partial RNA editing in mitochondrial genes of Beta vulgaris.

RNA editing is a process that modifies the information in transcripts of almost all angiosperm mitochondrial protein-coding genes. In order to determine the frequency and distribution of mitochondrial RNA editing in Beta vulgaris, cDNAs were sequenced and compared to the published genome sequence. 357 C to U conversions were identified across the 31 known protein genes and pseudogenes in Beta, the fewest so far for a plant mitochondrial genome. Editing patterns in the putative gene orf518 indicate that it is most likely a functional ccmC homolog, indicating that patterns of editing can be a useful determinant of gene functionality. orf518 also contains a triplicated repeat region whose members are nearly identical yet differentially edited, most likely due to differences in the sequence context of the editing sites. In addition, we show that partial editing in Beta is common at silent editing sites but rare at nonsilent editing sites, extending previous observations to a complete plant mitochondrial genome. Finally, the degree of partial editing observed for certain genes was dependent on the choice of primers used, demonstrating that care must be taken when designing primers for use in editing studies.

Base Sequence↗

Engineered virus-like particle-assembled Vegfa-targeting Cas9 ribonucleoprotein treatment alleviates neovascularization in wet age-related macular degeneration.

BACKGROUND: Age-related macular degeneration, particularly the wet form, is a leading cause of vision loss, characterized by vascular endothelial growth factor A (VEGFA) overproduction. Engineered virus-like particles (eVLPs) combine the efficiency of viral systems with the transient nature of non-viral platforms to offer a potential solution for delivering VEGFA-targeting genome editing enzymes in a safe and efficient manner. Here, we investigate the therapeutic efficacy of eVLPs for transient delivery of Vegfa-targeting Cas9 ribonucleoprotein in a laser-induced choroidal neovascularization mouse model of wet age-related macular degeneration. RESULTS: We find that Cas9-eVLPs enables efficient intracellular delivery in vitro, achieving up to 99% insertion and deletion frequency at Vegfa target locus and significant VEGFA protein downregulation in NIH/3T3 cells. A single subretinal injection of Cas9-eVLPs into the mouse retinal pigment epithelium effectively disrupts Vegfa expression, achieving an average indel efficiency of 16.7%. Compared to control groups, the laser-induced choroidal neovascularization mouse model exhibits significantly reduced choroidal neovascularization formation following Cas9-eVLPs intervention, and decreased VEGFA protein levels are detected in the retinal pigment epithelium. Furthermore, the retinal anatomical and functional toxicity are not affected after treatment. CONCLUSIONS: eVLPs exhibit the potential as a safe and efficient delivery platform for Cas9 ribonucleoproteins, achieving precise Vegfa downregulation and significant reduction in choroidal neovascularization in a mouse model of wet age-related macular degeneration. With transient delivery of gene editing enzymes, high editing efficiency, and minimal risk of genomic integration, eVLPs present a promising alternative to conventional delivery systems for advancing genome editing therapies in retinal diseases.

CRISPR-Associated Protein 9↗

Genome-wide CRISPR screens identify critical targets to enhance CAR-NK cell antitumor potency.

Adoptive cell therapy using engineered natural killer (NK) cells is a promising approach for cancer treatment, with targeted gene editing offering the potential to further enhance their therapeutic efficacy. However, the spectrum of actionable genetic targets to overcome tumor and microenvironment-mediated immunosuppression remains largely unexplored. We performed multiple genome-wide CRISPR screens in primary human NK cells and identified critical checkpoints regulating resistance to immunosuppressive pressures. Ablation of MED12, ARIH2, and CCNC significantly improved NK cell antitumor activity against multiple treatment-refractory human cancers in vitro and in vivo. CRISPR editing augmented both innate and CAR-mediated NK cell function, associated with enhanced metabolic fitness, increased secretion of proinflammatory cytokines, and expansion of cytotoxic NK cell subsets. Through high-content genome-wide CRISPR screening in NK cells, this study reveals critical regulators of NK cell function and provides a valuable resource for engineering next-generation NK cell therapies with improved efficacy against cancer.

Humans↗

CRISPRoff epigenome editing for programmable gene silencing in human cell lines and primary T cells.

The advent of CRISPR-based technologies has enabled the rapid advancement of programmable gene manipulation in cells, tissues, and whole organisms. An emerging platform for targeted gene perturbation is epigenetic editing, the direct editing of chemical modifications on DNA and histones that ultimately results in repression or activation of the targeted gene. In contrast to CRISPR nucleases, epigenetic editors modulate gene expression without inducing DNA breaks or altering the genomic sequence of host cells. Recently, we developed the CRISPRoff epigenetic editing technology that simultaneously establishes DNA methylation and repressive histone modifications at targeted gene promoters. Transient expression of CRISPRoff and the accompanying single guide RNAs in mammalian cells results in transcriptional repression of targeted genes that is memorized heritably by cells through cell division and differentiation. Here, we describe our protocol for the delivery of CRISPRoff through plasmid DNA transfection, as well as the delivery of CRISPRoff mRNA, into transformed human cell lines and primary immune cells. We also provide guidance on evaluating target gene silencing and highlight key considerations when utilizing CRISPRoff for gene perturbations. Our protocols are broadly applicable to other CRISPR-based epigenetic editing technologies, as programmable genome manipulation tools continue to evolve rapidly.

Humans↗

Establishment of CRISPR/Cas9-edited LEMD2 knock-in (UKWCHFi001-B-1) and knock-out (UKWCHFi001-B-2) iPSC lines to investigate the mechanisms of LEMD2-associated cardiomyopathy.

LEMD2 is an inner nuclear membrane protein. The pathogenic LEMD2 variant (NM_181336.4: c.38 T > G, p.L13R) has been associated with an inherited cardiomyopathy characterized by left ventricular dysfunction and severe arrhythmias. To gain more insights into this disease and investigate the role of LEMD2 more broadly, LEMD2 p.L13R knock-in (LEMD2-KI; UKWCHFi001-B-1) and knock-out (LEMD2-KO; UKWCHFi001-B-2) iPSC lines were generated in a healthy control iPSC (UKWCHFi001-B) line using CRISPR/Cas9 gene editing. Both new iPSC lines retained pluripotency, normal karyotypes, and differentiation potential, whereby expression of LEMD2 was successfully disrupted in LEMD2-KO cells. Thus, these lines provide a suitable model for analyzing LEMD2-associated diseases.

Humans↗