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Precise DGAT1 base editing and in-frame deletion reveal motif-specific regulation of seed oil biosynthesis in Arabidopsis.
Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final step in triacylglycerol (TAG) biosynthesis and is a key determinant of seed oil content and composition. To dissect the functional contribution of the conserved DGAT1 domains, we employed adenine and cytosine base editors and CRISPR/Cas9-mediated in-frame deletion to generate targeted alleles in Arabidopsis thaliana. A total of 25 single guide RNAs were designed to introduce precise nucleotide substitutions across functional domains, and the edited lines were screened using seed fluorescence and Sanger sequencing. Five base-edited (BE) DGAT1 mutants affecting acyl-CoA/CoA allosteric binding site (S124F, S123R/S124L), thiolase acyl-enzyme intermediate signature motif (L229P), diacylglycerol (DAG)-binding motif (W416C/R419Q, V418I), and an in-frame deletion in the intrinsically disordered N-terminal region (Δ49-76H) were characterized. Amino acid substitutions in the conserved domains led to distinct shifts in seed fatty acid profiles. Loss-of-function-like mutants (S123R/S124L, L229P, W416C/R419Q) reduced 18:1 and 20:1 levels and increased 18:3 levels, whereas putative gain-of-function mutants (S124F, V418I) enhanced 20:1 incorporation and elevated total oil content. Overexpression of DGAT1S124F and DGAT1V418I in the dgat1 mutant background further increased seed oil accumulation beyond that achieved with wild-type DGAT1. Structural modeling of DGAT1 proteins revealed the location of substituted amino acids and their interactions with surrounding residues, as well as the absence of putative N-terminal regulatory segment. These results demonstrate that precise base editing can modulate DGAT1 activity and TAG composition by targeting functional motifs, providing insights into the structure-function relationships of this key enzyme and offering strategies for metabolic engineering of seed oils.
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BEAR reveals that increased fidelity variants can successfully reduce the mismatch tolerance of adenine but not cytosine base editors.
Adenine and cytosine base editors (ABE, CBE) allow for precision genome engineering. Here, Base Editor Activity Reporter (BEAR), a plasmid-based fluorescent tool is introduced, which can be applied to report on ABE and CBE editing in a virtually unrestricted sequence context or to label base edited cells for enrichment. Using BEAR-enrichment, we increase the yield of base editing performed by nuclease inactive base editors to the level of the nickase versions while maintaining significantly lower indel background. Furthermore, by exploiting the semi-high-throughput potential of BEAR, we examine whether increased fidelity SpCas9 variants can be used to decrease SpCas9-dependent off-target effects of ABE and CBE. Comparing them on the same target sets reveals that CBE remains active on sequences, where increased fidelity mutations and/or mismatches decrease the activity of ABE. Our results suggest that the deaminase domain of ABE is less effective to act on rather transiently separated target DNA strands, than that of CBE explaining its lower mismatch tolerance.
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A panel of eGFP reporters for single base editing by APOBEC-Cas9 editosome complexes.
The prospect of introducing a single C-to-T change at a specific genomic location has become feasible with APOBEC-Cas9 editing technologies. We present a panel of eGFP reporters for quantification and optimization of single base editing by APOBEC-Cas9 editosomes. Reporter utility is demonstrated by comparing activities of seven human APOBEC3 enzymes and rat APOBEC1 (BE3). APOBEC3A and RNA binding-defective variants of APOBEC3B and APOBEC3H display the highest single base editing efficiencies. APOBEC3B catalytic domain complexes also elicit the lowest frequencies of adjacent off-target events. However, unbiased deep-sequencing of edited reporters shows that all editosomes have some degree of local off-target editing. Thus, further optimization is required to generate true single base editors and the eGFP reporters described here have the potential to facilitate this process.
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Phosphonoacetate Modifications Enhance the Stability and Editing Yields of Guide RNAs for Cas9 Editors.
CRISPR gene editing and control systems continue to emerge and inspire novel research and clinical applications. Advances in CRISPR performance such as optimizing the duration of activity in cells, tissues, and organisms, as well as limiting off-target activities, have been extremely important for expanding the utility of CRISPR-based systems. By investigating the effects of various chemical modifications in guide RNAs (gRNAs) at defined positions and combinations, we find that 2'-O-methyl-3'-phosphonoacetate (MP) modifications can be substantially more effective than 2'-O-methyl-3'-phosphorothioate (MS) modifications at the 3' ends of single-guide RNAs (sgRNAs) to promote high editing yields, in some instances showing an order of magnitude higher editing yield in human cells. MP-modified 3' ends are especially effective at promoting the activity of guide RNAs cotransfected with Cas messenger RNA (mRNA), as the gRNA must persist in cells until the Cas protein is expressed. We demonstrate such an MP enhancement for sgRNAs cotransfected with a BE4 mRNA for cytidine base editing and also demonstrate that MP at the 3' ends of prime editing guide RNAs (pegRNAs) cotransfected with PE2 mRNA can promote maximal prime editing yields. In the presence of serum, sgRNAs with MP-modified 3' ends showed marked improvements in editing efficiency over sgRNAs with MS-modified 3' ends codelivered with Cas9 mRNA and showed more modest improvements at enhancing the activity of transfected ribonucleoprotein (RNP) complexes. Our results suggest that MP should be considered as a performance-enhancing modification for the 3' ends of synthetic gRNAs, especially in situations where the guide RNAs may be susceptible to exonuclease-mediated degradation.
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Synonymous editing alters ion channel function, favoring prime editing for retinal disease correction.
Point mutations in the KCNJ13 gene cause autosomal recessive childhood blindness, Leber congenital amaurosis (LCA16), by disrupting Kir7.1 channel function. We describe the etiology of the LCA16 retinopathy phenotype in three patients from two unrelated families harboring a homozygous KCNJ13 missense mutation (c.431T>C, p.Leu144Pro). Our in silico prediction and in vitro validation using a human iPSC-derived retinal pigmented epithelium (RPE) model created via lipid nanoparticle-mediated delivery of the adenine base editor (ABE8e) demonstrated that the L144P mutation impairs Kir7.1 channel function and confirmed that non-viral biologic delivery is clinically translatable. We used two cytosine base editors (CBEs, BE4max-WTCas9 and evoCDA-SpCas9-NG) to correct this mutation in an L144P HEK293 stable cell model, achieving high on-target editing efficiency. However, our electrophysiological measurements showed minimal functional rescue of the channel in CBE-edited cells due to bystander nucleotide editing. Editing with evoCDA introduced a bystander missense mutation (L143F), whereas BE4max primarily generated silent mutations. Extended characterization of BE4max-edited cells revealed a distorted mRNA structure, altered half-life, and reduced abundance of cognate tRNA, all associated with these silent changes. In contrast, prime editing successfully restored channel function. Prime editors targeting the L144P locus achieved approximately 20% on-target editing without introducing bystander nucleotide editing or synonymous changes. Functional assessment demonstrated a strong genotype-phenotype correlation, with restored Kir7.1 channel activity observed in 28% of edited cells (12/43). Overall, these results highlight the importance of comprehensive functional validation of genome editing outcomes and emphasize the need for rigorous preclinical studies to translate therapeutic genome editing into first-in-human trials for genetically diverse diseases.
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Targeted Gene and Genome-Editing Strategies for Epilepsy: Experimental Advances and Translational Challenges.
Epilepsy affects more than 50 million individuals worldwide, and approximately one-third of patients remain refractory to existing antiseizure medications. Advances in gene therapy and genome editing have opened new possibilities for disease-modifying interventions that directly target the molecular and circuit-level mechanisms underlying epileptogenesis. Recent progress in central nervous system tropic viral vectors, non-viral delivery systems, and programmable genome-editing technologies has enabled precise manipulation of neuronal and glial function in preclinical epilepsy models. Strategies range from restoration of haploinsufficient genes implicated in monogenic epilepsies, such as SCN1A in Dravet syndrome, to modulation of neuronal excitability through engineered ion channels, neuropeptides, and astrocyte-based approaches. In parallel, CRISPR-derived platforms, including transcriptional activation and repression systems, base editing, and prime editing, offer new avenues for regulating gene expression in post-mitotic neurons without introducing double-strand DNA breaks. Despite these advances, significant translational challenges remain, including efficient and cell-type-specific delivery, long-term safety, and the risk of network-level side effects in the epileptic brain. This review critically examines recent gene therapy and genome-editing approaches for epilepsy, highlights key technological and biological barriers to clinical translation, and discusses emerging strategies that may enable durable and targeted treatments for drug-resistant epilepsies.
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CRISPR/Cas9-deaminase enables robust base editing in Rhodobacter sphaeroides 2.4.1.
BACKGROUND: CRISPR/Cas9 systems have been repurposed as canonical genome editing tools in a variety of species, but no application for the model strain Rhodobacter sphaeroides 2.4.1 was unveiled. RESULTS: Here we showed two kinds of programmable base editing systems, cytosine base editors (CBEs) and adenine base editors (ABEs), generated by fusing endonuclease Cas9 variant to cytosine deaminase PmCDA1 or heterodimer adenine deaminase TadA-TadA*, respectively. Using CBEs, we were able to obtain C-to-T mutation of single and double targets following the first induction step, with the efficiency of up to 97% and 43%; while the second induction step was needed in the case of triple target, with the screening rate of 47%. Using ABEs, we were only able to gain A-to-G mutation of single target after the second induction step, with the screening rate of 30%. Additionally, we performed a knockout analysis to identify the genes responsible for coenzyme Q10 biosynthesis and found that ubiF, ubiA, ubiG, and ubiX to be the most crucial ones. CONCLUSIONS: Together, CBEs and ABEs serve as alternative methods for genetic manipulation in Rhodobacter sphaeroides and will shed light on the fundamental research of other bacteria that are hard to be directly edited by Cas9-sgRNA.
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Engineered CRISPR-Cas12a variants with increased activities and improved targeting ranges for gene, epigenetic and base editing.
Broad use of CRISPR-Cas12a (formerly Cpf1) nucleases1 has been hindered by the requirement for an extended TTTV protospacer adjacent motif (PAM)2. To address this limitation, we engineered an enhanced Acidaminococcus sp. Cas12a variant (enAsCas12a) that has a substantially expanded targeting range, enabling targeting of many previously inaccessible PAMs. On average, enAsCas12a exhibits a twofold higher genome editing activity on sites with canonical TTTV PAMs compared to wild-type AsCas12a, and we successfully grafted a subset of mutations from enAsCas12a onto other previously described AsCas12a variants3 to enhance their activities. enAsCas12a improves the efficiency of multiplex gene editing, endogenous gene activation and C-to-T base editing, and we engineered a high-fidelity version of enAsCas12a (enAsCas12a-HF1) to reduce off-target effects. Both enAsCas12a and enAsCas12a-HF1 function in HEK293T and primary human T cells when delivered as ribonucleoprotein (RNP) complexes. Collectively, enAsCas12a provides an optimized version of Cas12a that should enable wider application of Cas12a enzymes for gene and epigenetic editing.
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Precision breeding in a changing climate: unlocking resilience through omics and gene editing.
Climate change, rising global food demand, and shrinking resources require transformative innovations in crop breeding. This review outlines recent advances in new breeding technologies (NBTs), including molecular markers, genome-wide association studies (GWAS), genomic selection (GS), next-generation sequencing (NGS), and gene editing (GE) tools such as the clustered regularly interspaced short palindromic repeat (CRISPR/Cas), base editing, and prime editing. These methods enable the accurate improvement of traits, thereby accelerating the development of crops resistant to both abiotic and biotic stresses. The integration of multi-omics platforms, including genomics, transcriptomics, proteomics, metabolomics, and phenomics, provides a comprehensive framework for deciphering and manipulating complex trait architectures. Artificial intelligence (AI) and machine learning (ML) enhance precision breeding by providing data-driven insights and enabling the forecasting of traits. Emphasis is also placed on combining gene editing with other strategies, such as speed breeding, to accelerate the development of traits. This review underscores the importance of an integrated systems biology approach that combines multi-omics, gene editing, AI, and speed breeding to accelerate the development of climate-resilient, high-yielding, and nutritionally enhanced crops. The integration of these innovative technologies holds great promise for addressing global food security, environmental sustainability, and agricultural resilience in the face of climate change. A strategic framework for the future of plant breeding is outlined, emphasizing the importance of interdisciplinary collaboration in building a sustainable agricultural future.
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Genome Editing Using CRISPR/Cas9 System in the Rice Blast Fungus.
Fast and flexible genome manipulation is a powerful strategy for an in-depth understanding of molecular mechanisms in biological research. In recent years, CRISPR/Cas9-mediated genome editing has been used as a reliable genome manipulation method in a broad range of biological research including studies of filamentous fungi. The CRISPR/Cas9 system comprises a single-guide RNA (sgRNA) and a Cas9 protein, and the Cas9/sgRNA complex catalyzes a DNA double-strand break at the desired genomic locus. This protocol describes a fundamental CRISPR/Cas9 methodology that includes the design of the target sequence, construction of the CRISPR/Cas9 expression vector, and transformation for genome editing in Pyricularia (Magnaporthe) oryzae. This allows efficient targeted gene disruption, base editing, and reporter gene knock-in without any additional modifications of the host components. This protocol would be suitable for applying other CRISPR/Cas technologies and various functional genomics in P. oryzae.
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