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LDLR Variant Classification Through Activity-Normalized Prime Editing Screening.

BACKGROUND: Inherited variants in the LDL (low-density lipoprotein) receptor (LDLR) gene are the most common cause of familial hypercholesterolemia, significantly increasing coronary artery disease risk. Early identification of pathogenic LDLR variants enables prompt lipid-lowering therapy and cascade testing of at-risk relatives; however, most LDLR variants observed in the population have uncertain or absent clinical classifications, leaving many patients without actionable information. METHODS: We developed the first activity-normalized prime editing screening pipeline to measure the impact of 5184 LDLR coding variants on LDL-cholesterol (LDL-C) uptake. Each prime editing guide RNA is paired with a genotypic outcome reporter to correct for variable editing efficiency, overcoming a key limitation of previous pooled genome editing screens. A statistical framework further improves variant effect estimates by jointly analyzing all missense variants at each amino acid position. RESULTS: We show that prime editing of the reporter construct correlates with endogenous variant installation frequency, validating the activity normalization approach. The resulting scores capture a continuous spectrum of functional effects, robustly separate pathogenic versus benign ClinVar variants, and show concordance with LDL-C levels in UK Biobank participants. We calibrate functional evidence strengths to the ACMG/AMP variant interpretation framework, enabling integration into a clinical variant classification workflow. By combining functional, computational, population, and contextual evidence, 322 of 434 LDLR variants currently classified as variants of uncertain significance, conflicting, or absent from ClinVar appear to meet evidence thresholds for reclassification and can be prioritized for expert review, substantially expanding the pool of actionable variant classifications. The screen also reveals a cluster of gain-of-function variants in LDLR class A repeat 5, at least some of which enhance LDL-C uptake through increased apolipoprotein B interaction, with implications for therapeutic genome editing. Last, prime editing uniquely detects splice-altering coding variants missed by cDNA-based screens and pathogenicity predictors, revealing an advantage of endogenous variant installation. CONCLUSIONS: Altogether, activity-normalized prime editing provides a scalable framework for LDLR variant classification that substantially expands the proportion of variants with evidence for genetic diagnosis and reveals novel biology with therapeutic relevance.

CRISPR screening

Cell-type-specific response to silicon treatment in soybean leaves revealed by single-nucleus RNA sequencing and targeted gene editing.

Mineral nutrient uptake and deposition profoundly influence plant development, stress resilience, and productivity. Silicon (Si), though classified as a non-essential element, significantly influences a plant's physiology, particularly in fortifying defense responses and mitigating stress. While the genetic and molecular mechanisms of Si uptake and transport are well studied in monocots, particularly rice, their role in dicot species, such as soybean, remains unclear at the cellular and molecular levels. In this study, we utilized single-nucleus RNA sequencing (snRNA-seq) to dissect cellular responses to Si accumulation in soybean leaves. We identified distinct cellular populations, including a unique Si-induced or Si-associated cell cluster within vascular cells, suggesting a specialized mechanism of Si distribution. Si treatment notably induced the expression of defense-related genes, with a pronounced enrichment in vascular cells, underscoring their pivotal role in activating plant defense mechanisms. Moreover, Si modulated the expression of genes involved in phytoalexin biosynthesis, salicylic acid, and immune receptor signaling, suggesting transcriptional priming of genes involved in defense responses. Further investigation of Si transporters revealed precise expression of an Si efflux gene in epidermal cells in response to Si treatment. We also validated the role of efflux Si transporters using a Xenopus oocyte assay and CRISPR/Cas9 genome editing of composite soybean plant roots. This study provides critical insights into the biotic stress regulatory networks influenced by Si treatment in soybean leaves at the single-cell level, thus laying the foundation for enhancing stress tolerance through optimized mineral nutrient uptake.

Glycine max

Dense RNA motif modifications enable robust in vivo prime editing and enhance efficiencies of diverse editing systems.

Prime editing holds promise for therapeutic applications. However, viral delivery of the prime editor presents challenges for clinical translation due to concerns regarding long-term expression. Meanwhile, systemic delivery using non-viral vectors has been limited by low efficiency, the need for repeated injections and reliance on doses that exceed clinically translatable levels. Here we develop engineered prime editing guide RNAs (pegRNAs) with densely modified RNA motifs and demonstrate their application for efficient in vivo prime editing. By systemically delivering the prime editor in RNA format via a single injection of lipid nanoparticles, we achieved nearly 70% editing efficiency in the bulk mouse liver, indicating successful editing of the majority of hepatocytes. Notably, a single injection at a clinically translatable lipid nanoparticle dose was sufficient to suppress target protein expression in vivo, resulting in a near 80-fold increase in editing efficiency compared with conventional end-modified pegRNAs. Furthermore, incorporating densely modified RNA motifs, including the widely used MS2 motif, proved broadly applicable across various RNA sequences and split RNA-guided genome editing platforms, resulting in up to an 11-fold increase in base editing efficiency. These findings present a generalizable approach for enhancing the therapeutic potential of prime editing and expanding the utility of RNA-based therapeutics.

Journal Article

Genome editing with programmable base editors in human cells.

Genome editing has garnered significant attention over the last decade, resulting in a massive expansion of the genome engineering toolbox. Base editors encompass a class of tools that enable installing single-nucleotide changes in genomic DNA without the use of double-strand breaks. With the ever-increasing development of new and/or improved base editor systems, it is easy to be overwhelmed by the abundance of options. Here, we provide clear guidance to facilitate the selection of a base editor and to design guide RNAs (gRNAs) to suit various needs. Additionally, we describe in detail how to generate gRNA plasmids, transfect various mammalian cell types, and evaluate editing efficiencies. Finally, we give alternative methods and troubleshooting tips for some common pitfalls encountered during base editing.

Humans

A quick guide to evaluating prime editing efficiency in mammalian cells.

According to the Clinvar database, modeling the diseases associated with pathogenic mutations requires the installation of base substitutions, small insertions or deletions. Prime editor (PE) was recently developed to precisely install any base substitutions and/or small insertions/deletions (indels) in mammalian cells and animals without requiring DSBs or donor DNA templates. PE also offers greater editing and targeting flexibility compared to other precision CRISPR editing methods because the versatile editing information is encoded in the reverse-transcription template of its prime editing guide RNA. However, optimal PE system selection and experimental design can be complex, and there are various factors that can affect PE efficiency. This chapter serves as a rapid entry-level guideline for the application of PE, providing an experimental framework for using PE at a specific genomic locus. RUNX1 was selected as a representative target site to illustrate the detailed methodology for constructing PE plasmids and the process of transfecting these plasmids into 293FT cells. We further examined the efficiency of PE-mediated genome editing in mammalian cells by using next-generation sequencing.

Gene Editing

CRISPR/Cas9-Mediated Gene-Knockout and In Situ Complementation System for Phytophthora sojae.

The establishment of reliable and efficient systems for genome editing in Phytophthora is very important for studying gene functions. Here, step-by-step methods for CRISPR/Cas9-based gene knockout and in situ complementation for Phytophthora sojae are presented. These steps include the sgRNA design, Cas9-sgRNA plasmid construction, homologous replacement, complementation vector construction, P. sojae transformation, and detection of mutations for both gene knockout and in situ complementation. These methods may also potentially be adapted for other Phytophthora species.

Phytophthora

RNA-DNA hybrid binding domain broadens the editing window of base editors.

Adenine base editors (ABEs) and cytosine base editors (CBEs) are prominent tools for precise genome editing but are hindered by limited editing activity at positions proximal to the protospacer adjacent motif (PAM). This study investigates the potential of enhancing base editors editing activity by fusing them with RNA-DNA hybrid binding domains (RHBDs). Specifically, fusing ABE8e with the RHBD of Homo sapiens RNaseH1 (RHBD1) significantly increased A-to-G editing efficiency in the PAM-proximal region (A9-A15) by up to 3.5-fold, while reducing off-target cytosine editing. Additionally, RHBD1 is compatible with ABEmax, BE4max, and dual base editor (eA&C-BEmax), enhancing their editing activity at the PAM-proximal bases. Notably, RHBD1-fused BE4max led to a 3.1-fold improvement in C-to-T editing efficiency at PAM-proximal region (C9-C12). Furthermore, we demonstrated that RHBD1-fused ABE8e could effectively edit disease-related single nucleotide variations (SNVs) in human cells and validated its efficacy in adult mouse liver. These findings highlight the significance of the RHBD in expanding editing window and the applicability of base editors for gene therapy and disease modeling.

Gene Editing

Identification of editing positions in the ndhB transcript from maize chloroplasts reveals sequence similarities between editing sites of chloroplasts and plant mitochondria.

A comparison of the nucleotide sequences from genomic DNA and cDNA of the ndhB gene from maize chloroplasts shows that the ndhB transcript is edited by C-to-U transitions at six positions which appear to exist as editing sites also in the chloroplast ndhB genes from rice and tobacco but not from liverwort. In order to identify possible sequence determinants necessary for editing, the sequences surrounding the newly identified ndhB and previously identified ndhA editing sites were compared with each other and with editing sites observed in plant mitochondrial transcripts. Among the chloroplast editing sites two closely positioned ndhB sites show similarity by sharing a common octanucleotide. The existence of the identical octanucleotide in the ndhJ gene whose transcript is not edited at the respective position, shows, however, that this octanucleotide is not sufficient to elicit the editing process. On the other hand, several of the chloroplast editing sites show sequence similarities with certain sets of consensus sequences reported earlier for editing sites of plant mitochondria. This supports the view that the editing processes of both plant organelles share common components and/or mechanistic steps and that the consensus sequences are part of the determinants necessary for editing.

Amino Acid Sequence

Measuring double-strand break repair events in mammalian cells with multi-target CRISPR.

A mechanistic understanding of the different pathways involved in the repair of DSBs is a timely, yet challenging task. CRISPR-Cas9 is a powerful tool to induce DNA double-strand breaks (DSB) at defined genomic locations to study the ensuing repair response, but Cas9 studies are typically limited by i) low-throughput induction of DSB, by targeting only one or a few genomic sites, or ii) the use of genetically integrated reporter systems, which do not always reflect endogenous phenotypes. To address these limitations, we developed multi-target CRISPR, a Cas9-based tool to controllably induce DSBs in high-throughput at endogenous sites, by leveraging repetitive genomic regions. In this Chapter, we describe how to design and execute a multi-target CRISPR experiment. We also detail how to analyze next-generation sequencing data for characterization of DSB repair events at multiple cut sites. We envision that multi-target CRISPR will become a valuable tool for the study of mammalian DSB repair mechanisms.

DNA Breaks, Double-Stranded

Mouse U14 snRNA is a processed intron of the cognate hsc70 heat shock pre-messenger RNA.

U14 snRNA is a small nucleolar RNA species essential for eukaryotic pre-rRNA processing. We have previously shown that the mouse U14 snRNA genes are positioned within introns 5, 6, and 8 on the coding strand of the constitutively expressed cognate hsc70 heat shock gene. This genomic organization suggested the possibility that U14 snRNAs are transcribed as part of the hsc70 pre-mRNA and then excised from the intron to yield mature U14 snRNA species. To test this hypothesis directly, we have microinjected Xenopus oocytes with hsc70 pre-mRNA transcripts possessing intron 5 and the encoded U14 snRNA sequence. Processing results demonstrate that, in addition to the splicing of upstream and downstream exons, a mature 87 nt U14 snRNA is excised from the intron. Accurate excision of U14 snRNA from hsc70 intron 5 can occur in the absence of splicing. These results demonstrate a biosynthetic pathway for an snRNA species and provide a novel example of a eukaryotic pre-mRNA intron that is processed to produce a stable, biologically functional RNA species.

Amino Acid Sequence

m6A modification of mutant huntingtin RNA promotes the biogenesis of pathogenic huntingtin transcripts.

In Huntington's disease (HD), aberrant processing of huntingtin (HTT) mRNA produces HTT1a transcripts that encode the pathogenic HTT exon 1 protein. The mechanisms behind HTT1a production are not fully understood. Considering the role of m6A in RNA processing and splicing, we investigated its involvement in HTT1a generation. Here, we show that m6A methylation is increased before the cryptic poly(A) sites (IpA1 and IpA2) within the huntingtin RNA in the striatum of Hdh+/Q111 mice and human HD samples. We further assessed m6A's role in mutant Htt mRNA processing by pharmacological inhibition and knockdown of METTL3, as well as targeted demethylation of Htt intron 1 using a dCas13-ALKBH5 system in HD mouse cells. Our data reveal that Htt1a transcript levels are regulated by both METTL3 and the methylation status of Htt intron 1. They also show that m6A methylation in intron 1 depends on expanded CAG repeats. Our findings highlight a potential role for m6A in aberrant splicing of Htt mRNA.

Huntingtin Protein

Enhanced cleavage of genomic CCR5 using CASX2Max.

Development of novel CRISPR/Cas systems enhances opportunities for gene editing to treat infectious diseases, cancer, and genetic disorders. CasX2 (PlmCas12e) belongs to the class II CRISPR system derived from Planctomycetes, a non-pathogenic bacterium present in aquatic and terrestrial soils and offers several advantages as a potential therapeutic CRISPR system over Streptococcus pyogenes Cas9 (SpCas9) and Staphylococcus aureus Cas9 (SaCas9). These advantages include its smaller size, distinct protospacer adjacent motif (PAM) requirements, staggered cleavage cuts that promote homology-directed repair, and the absence of pre-existing immunity in humans. We compared the cleavage efficiency and double-stranded break repair characteristics between CasX2 and CasX2Max, a recently generated CasX2 variant with three amino acid substitutions, for targeting CCR5, a gene that encodes the CCR5 receptor important for HIV-1 infection. Two single guide RNAs (sgRNAs) were designed that flank the 32 bases deleted in the natural CCR5 ∆32 mutation. Nanopore sequencing demonstrated that CasX2 using sgRNAs with spacers of 17 nucleotides (nt), 20 nt or 23 nt in length were ineffective at cleaving genomic CCR5. In contrast, CasX2Max using sgRNAs with 20 nt and 23 nt spacer lengths, enabled cleavage of genomic CCR5. Structural modelling indicated that two of the CasX2Max amino acid substitutions enhanced sgRNA-DNA duplex stability, while the third improved DNA strand alignment within the catalytic site. These structural changes likely underlie the increased activity of CasX2Max in cellular gene excision. In sum, CasX2Max consistently outperformed native CasX2 across all assays and represents a superior gene-editing platform for therapeutic applications.

Humans

CRISPR/Cpf1-mediated knockout of FLG in human induced pluripotent stem cells generates a model for studying epidermal barrier dysfunction.

Loss of filaggrin (FLG) function impairs skin barrier formation and contributes to common inflammatory skin diseases. In this study, we established a FLG knockout human induced pluripotent stem cell (iPSC) line based on KOLF2.1 J using CRISPR/Cas12a (Cpf1)-mediated genome editing. A guide RNA targeting exon 2 introduced a homozygous mutation, which was confirmed by sequencing. The edited cells maintained typical pluripotent stem cell morphology, expressed key undifferentiated markers, and retained the ability to differentiate into all three germ layers. Karyotype and copy number variation (CNV) analyses confirmed genomic stability and parental origin; the cells were free of mycoplasma. This cell line enables studies of FLG-associated skin biology and pathology.

Humans

Optimized TadA-derived base editors efficiently manipulate mRNA splicing by A-to-G and C-to-K editing in potato.

Pre-messenger RNA (pre-mRNA) splicing is a critical mechanism for post-transcriptional regulation in plants. Through alternative splicing, plants produce diverse transcriptomes and proteomes that finely regulate development as well as responses to biotic and abiotic stresses. However, modulating the generation of specific splicing isoforms for functional characterization remains challenging, particularly in the non-model crop potato. Here, we show that two optimized TadA-derived base editors efficiently induce diverse mRNA splice variants by targeting specific splice sites. By evaluating multiple adenosine deaminases and performing multi-dimensional optimization, we developed an efficient adenine base editor RTF-ABE8e for potato. RTF-ABE8e achieved 100% editing efficiency at two StDL1 target sites in stable transgenic potato, with homozygous editing frequencies as high as 93.3% and 91.1%, respectively. We also developed RTF-TadDE, a dual-base editor based on a TadA-derived dual deaminase, for A-to-G and C-to-K (K = T/G) mutations in potato with an overall editing efficiency comparable to that of RTF-ABE8e. By targeting different splice sites with these base editors, we obtained diverse splicing isoforms carrying premature termination codons (PTCs) at StDL1 and StPDS and robust mutant phenotypes. These base editors enable efficient and precise editing of splice sites to trigger missplicing, making them powerful tools for manipulating splicing in plants.

Solanum tuberosum

Base editing for precision therapeutics.

Base editing (BE), the precise installation of single-nucleotide changes in DNA or RNA without inducing double-strand breaks, holds substantial therapeutic promise for correcting single-nucleotide variants, which constitute more than half of the known pathogenic genetic variants. Recent advances have improved base editor specificity, efficiency, and delivery, enabling clinically oriented procedures. Clinically, BE has shown early success or strong translational promise in sickle cell disease, β-thalassemia, leukemia (via CAR T and epitope engineering), hypercholesterolemia (PCSK9 and ANGPTL3), alpha-1-antitrypsin deficiency, and glycogen storage disease type Ia. Key remaining challenges include bystander editing within the activity window, residual off-target DNA and RNA editing, delivery constraints (payload size, tissue targeting, and redosing limits), immunogenicity, and the need for durable long-term safety evidence across relevant cell types and disease contexts. Continued technological refinements, careful preclinical validation, and rigorous clinical assessment will be essential to fully realize BE's transformative potential in precision medicine.

Humans

Next-generation macrophage engineering in cancer therapy: From TAM reprogramming to CAR-macrophages.

Macrophages are central regulators of the tumor microenvironment (TME), shaping immune suppression, angiogenesis, metabolism, and therapeutic resistance in solid cancers. While early strategies sought to deplete tumor-associated macrophages (TAMs) or block monocyte recruitment, limited efficacy and compensatory mechanisms revealed the need for functional reprogramming rather than elimination. Recent advances in viral vectors, CRISPR-Cas genome editing, and RNA-based delivery platforms have enabled precise genetic modification of macrophages, giving rise to chimeric antigen receptor macrophages (CAR-Ms) and related engineered products. Beyond antigen targeting, effective macrophage engineering requires stabilization of pro-inflammatory identity, resistance to tumor-induced repolarization, metabolic reinforcement, and integration of checkpoint modulation pathways. This review synthesizes current strategies across DNA, mRNA, and siRNA-based platforms, highlighting convergent design principles that connect TAM reprogramming with CAR-M development. We discuss reshaping phagocytosis checkpoints, metabolic and transcriptional stabilization, cytokine augmentation, and synthetic receptor architecture, emphasizing combinatorial and context-aware engineering, while proposing new candidate gene targets. Engineered macrophages are thus evolving from simple effector cells into programmable immune coordinators capable of converting immunologically "cold" tumors into inflamed, therapy-responsive niches.

CAR-M

Innovative strategies for mitochondrial dysfunction in myeloproliferative neoplasms a step toward precision medicine.

Myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoietic stem cells characterized by aberrant proliferation of myeloid lineages, driven primarily by mutations in JAK2, CALR, and myeloproliferative leukemia, leading to constitutive activation of the JAK-STAT pathway. Emerging evidence highlights mitochondrial dysfunction as a key factor in MPN pathogenesis, contributing to increased reactive oxygen species production, mitochondrial DNA mutations, and dysregulated mitochondrial dynamics, which collectively promote clonal expansion and apoptosis resistance. Targeting mitochondrial pathways has gained attention as a therapeutic strategy, with approaches including mitochondria-targeted antioxidants, metabolic inhibitors, and modulation of mitophagy and mitochondrial fission/fusion dynamics. However, challenges such as drug delivery specificity, therapeutic resistance, and off-target effects remain significant. Recent advances in precision medicine, incorporating genomic, transcriptomic, and proteomic profiling, offer a more personalized approach to MPN treatment by tailoring interventions to individual mutation patterns. Additionally, novel therapeutic strategies, including gene editing technologies, RNA-based therapies, and nanoparticle-mediated drug delivery systems, hold promise for overcoming current treatment limitations. The integration of artificial intelligence in drug discovery and biomarker identification further enhances the potential for targeted therapies. Future research should focus on refining these strategies, developing reliable biomarkers for patient stratification, and exploring combination therapies that enhance treatment efficacy while minimizing adverse effects. By addressing mitochondrial dysfunction as an underlying driver of MPNs, these emerging approaches have the potential to improve disease management, extend patient survival, and enhance quality of life. Also, this new approach of precision medicine allows patient stratification and ensures that treatments are formed according to the individual disease biology of each patient, which results in overall better outcomes.

combination drug therapy

From Sequential Gland Replacement to Recurrent Gland Coordination: A Comparative Framework for Subventral and Dorsal Oesophageal Gland Effectors Across Plant-Parasitic Nematode Lifestyles.

Plant-parasitic nematodes manipulate host tissues through stylet-secreted gene products synthesised principally in two subventral and one dorsal oesophageal gland. Earlier reviews have catalogued effector repertoires, described feeding-site formation, and explained how individual effectors modify host defence, development, and metabolism. However, the temporal coordination of the gland cells themselves has not been comparatively synthesised across parasitic lifestyles. This review therefore advances a gland-centred, lifestyle-dependent framework. In sedentary endoparasites, available evidence supports a pronounced developmental transition: subventral gland products dominate penetration and migration, whereas dorsal gland products become increasingly important during feeding-site initiation and maintenance. Migratory endoparasites repeatedly penetrate, migrate, and feed without establishing permanent feeding cells; their gland activity is consequently predicted to be recurrent and overlapping rather than a one-way replacement. Ectoparasites likewise require behaviour-dependent coordination during repeated probing and external feeding, although direct gland localisation evidence remains limited. We integrate gland origin, secretion chemistry, infection stage, and parasitic behaviour across root-knot, cyst, citrus, false root-knot, lesion, burrowing, and ectoparasitic nematodes. The synthesis distinguishes experimentally demonstrated gland localisation from evidence-weighted inference and formulates testable predictions for comparative gland transcriptomics, spatial expression, and functional silencing. This framework also identifies gland activation, secretion, and stage-critical products as targets for RNA interference, genome editing, resistance breeding, and sustainable nematode management. The principal novelty is therefore not another catalogue of nematode effectors, but a comparative model explaining when and why subventral and dorsal glands exchange, retain, or alternate their functions across contrasting parasitic lifestyles.

dorsal gland