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Abstract The discovery of CRISPR-Cas systems has paved the way for advanced gene editing tools. However, traditional Cas discovery methods relying on sequence similarity may miss distant homologs and aren’t suitable for functional recognition. With protein large language models (LLMs) evolving, there is potential for Cas system modeling without extensive training data. Here, we introduce CHOOSER (Cas HOmlog Observing and SElf-processing scReening), an AI framework for alignment-free discovery of CRISPR-Cas systems with self-processing pre-crRNA capability using protein foundation models. By using CHOOSER, we identify 11 Casλ homologs, nearly doubling the known catalog. Notably, one homolog, EphcCasλ, is experimentally validated for self-processing pre-crRNA, DNA cleavage, and trans-cleavage, showing promise for CRISPR-based pathogen detection. This study highlights an innovative approach for discovering CRISPR-Cas systems with specific functions, emphasizing their potential in gene editing.

Abstract Genetic testing is crucial for precision cancer medicine. However, detecting multiple same-site insertions or deletions (indels) is challenging. Here, we introduce CoHIT (Cas12a-based One-for-all High-speed Isothermal Test), a one-pot CRISPR-based assay for indel detection. Leveraging an engineered AsCas12a protein variant with high mismatch tolerance and broad PAM scope, CoHIT can use a single crRNA to detect multiple NPM1 gene c.863_864 4-bp insertions in acute myeloid leukemia (AML). After optimizing multiple parameters, CoHIT achieves a detection limit of 0.01% and rapid results within 30 minutes, without wild-type cross-reactivity. It successfully identifies NPM1 mutations in 30 out of 108 AML patients and demonstrates potential in monitoring minimal residual disease (MRD) through continuous sample analysis from three patients. The CoHIT method is also competent for detecting indels of KIT, BRAF, and EGFR genes. Integration with lateral flow test strips and microfluidic chips highlights CoHIT’s adaptability and multiplexing capability, promising significant advancements in clinical cancer diagnostics.

Abstract Base editors (BEs) are a recent generation of genome editing tools that couple a cytidine or adenosine deaminase activity to a catalytically impaired Cas9 moiety (nCas9) to enable specific base conversions at the targeted genomic loci. Given their strong application potential, BEs are under active developments toward greater levels of efficiency and safety. Here, a previously overlooked nCas9‐centric strategy is explored for enhancement of BE. Based on a cytosine BE (CBE), 20 point mutations associated with nCas9‐target interaction are tested. Subsequently, from the initial positive X‐to‐arginine hits, combinatorial modifications are applied to establish further enhanced CBE variants (1.1–1.3). Parallel nCas9 modifications in other versions of CBEs including A3A‐Y130F‐BE4max, YEE‐BE4max, CGBE, and split‐AncBE4max, as well as in the context of two adenine BEs (ABE), likewise enhance their respective activities. The same strategy also substantially improves the efficiencies of high‐fidelity nCas9/BEs. Further evidence confirms that the stabilization of nCas9‐substrate interactions underlies the enhanced BE activities. In support of their translational potential, the engineered CBE and ABE variants respectively enable 82% and 25% higher rates of editing than the controls in primary human T‐cells. This study thus demonstrates a highly adaptable strategy for enhancing BE, and for optimizing other forms of Cas9‐derived tools.

Abstract Rapid and accurate diagnostic tests are fundamental for improving patient outcomes and combating infectious diseases. The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) Cas12a‐based detection system has emerged as a promising solution for on‐site nucleic acid testing. Nonetheless, the effective design of CRISPR RNA (crRNA) for Cas12a‐based detection remains challenging and time‐consuming. In this study, we propose an enhanced crRNA design system with deep learning for Cas12a‐mediated diagnostics, referred to as EasyDesign. This system employs an optimized convolutional neural network (CNN) prediction model, trained on a comprehensive data set comprising 11,496 experimentally validated Cas12a‐based detection cases, encompassing a wide spectrum of prevalent pathogens, achieving Spearman's ρ = 0.812. We further assessed the model performance in crRNA design for four pathogens not included in the training data: Monkeypox Virus, Enterovirus 71, Coxsackievirus A16, and Listeria monocytogenes. The results demonstrated superior prediction performance compared to the traditional experiment screening. Furthermore, we have developed an interactive web server (https://crispr.zhejianglab.com/) that integrates EasyDesign with recombinase polymerase amplification (RPA) primer design, enhancing user accessibility. Through this web‐based platform, we successfully designed optimal Cas12a crRNAs for six human papillomavirus (HPV) subtypes. Remarkably, all the top five predicted crRNAs for each HPV subtype exhibited robust fluorescent signals in CRISPR assays, thereby suggesting that the platform could effectively facilitate clinical sample testing. In conclusion, EasyDesign offers a rapid and reliable solution for crRNA design in Cas12a‐based detection, which could serve as a valuable tool for clinical diagnostics and research applications.

Abstract Prime editing allows precise installation of any single base substitution and small insertions and deletions without requiring homologous recombination or double-strand DNA breaks in eukaryotic cells. However, the applications in bacteria are hindered and the underlying mechanisms that impede efficient prime editing remain enigmatic. Here, we report the determination of vital cellular factors that affect prime editing in bacteria. Genetic screening of 129 Escherichia coli transposon mutants identified sbcB, a 3ʹ→5ʹ DNA exonuclease, as a key genetic determinant in impeding prime editing in E. coli, combinational deletions of which with two additional 3ʹ→5ʹ DNA exonucleases, xseA and exoX, drastically enhanced the prime editing efficiency by up to 100-fold. Efficient prime editing in wild-type E. coli can be achieved by simultaneously inhibiting the DNA exonucleases via CRISPRi. Our results pave the way for versatile applications of prime editing for bacterial genome engineering.

Abstract Inverse Protein Folding (IPF) is an important task of protein design, which aims to design sequences compatible with a given backbone structure. Despite the prosperous development of algorithms for this task, existing methods tend to rely on noisy predicted residues located in the local neighborhood when generating sequences. To address this limitation, we propose an entropy-based residue selection method to remove noise in the input residue context. Additionally, we introduce ProRefiner, a memory-efficient global graph attention model to fully utilize the denoised context. Our proposed method achieves state-of-the-art performance on multiple sequence design benchmarks in different design settings. Furthermore, we demonstrate the applicability of ProRefiner in redesigning Transposon-associated transposase B, where six out of the 20 variants we propose exhibit improved gene editing activity.

Abstract CAR T cell therapy has been successfully used in the treatment of hematological malignancies, and the strategy that deletion of inhibitory receptor on the CAR T cell surface, such as PD-1, greatly enhance the antitumor effects. Here, we describe a one-step electroporation for the co-transfection of Cas9:sgRNA and CAR plasmids on primary T cells to demonstrate the effect of SHP-1 deletion in CAR T cells. By using PiggyBac Transposase system, we can achieve more than 90% of T cells express CAR gene and nearly 60% SHP-1 knockout efficiency in T cells. We show that knockout of SHP-1 in CD133 CAR T cells resulted in significantly improve the cytolysis effect on CD133 positive glioma cell lines. We further demonstrate that the enhanced antitumor efficacy of SHP-1 deletion is due to the increased release of TNF-α, IL-2 and IFN-γ in vitro. Finally, we evaluated the biosafety of Cas9 genome editing and did not find any insertions of Cas9 and obvious editing in off-target sites in CAR T cells. These data provide an approach for achieving both intracellular inhibitory molecule, SHP-1 deletion and CD133 CAR gene over-expression in human T cells. And SHP-1 could be a new potential target for adoptive CAR T cells immunotherapy.

Abstract Haploinsufficient mutation in arginine and glutamine-rich protein 1 (Arglu1), a newly identified pre-mRNA splicing regulator, may be linked to neural developmental disorders associated with mental retardation and epilepsy in human patients, but the underlying causes remain elusive. Here we show that ablation of Arglu1 promotes radial glial cell (RG) detachment from the ventricular zone (VZ), leading to ectopic localized RGs in the mouse embryonic cortex. Although they remain proliferative, ectopic progenitors, as well as progenitors in the VZ, exhibit prolonged mitosis, p53 upregulation and cell apoptosis, leading to reduced neuron production, neuronal loss and microcephaly. RNA seq analysis reveals widespread changes in alternative splicing in the mutant mouse embryonic cortex, preferentially affecting genes involved in neuronal functions. Mdm2 and Mdm4 are found to be alternatively spliced at the exon 3 and exon 5 respectively, leading to absence of the p53-binding domain and nonsense-mediated mRNA decay (NMD) and thus relieve inhibition of p53. Removal of p53 largely rescues the microcephaly caused by deletion of Arglu1. Our findings provide mechanistic insights into cortical malformations of human patients with Arglu1 haploinsufficient mutation.

An animal model harboring pathogenic mitochondrial DNA (mtDNA) mutations is important to understand the biological links between mtDNA variation and mitochondrial diseases. DdCBE, a DddA-derived cytosine base editor, has been utilized in zebrafish, mice, and rats for tC sequence-context targeting and human mitochondrial disease modeling. However, human pathogenic mtDNA mutations other than the tC context cannot be manipulated. Here, we screened the combination of different DdCBE pairs at pathogenic mtDNA mutation sites with nC (n for a, g, or c) context and identified that the left-G1333C (L1333C) + right G1333N (R1333N) pair could mediate C⋅G-to-T⋅A conversion effectively at aC sites in rat C6 cells. The editing efficiency at disease-associated mtDNA mutation sites within aC context was further confirmed to be up to 67.89% in vivo. Also, the installed disease-associated mtDNA mutations were germline transmittable. Moreover, the edited rats showed impaired cardiac function and mitochondrial function, resembling human mitochondrial disease symptoms. In summary, for the first time, we expanded the DdCBE targeting scope to an aC motif and installed the pathogenic mutation in rats to model human mitochondrial diseases.

Adenine base editors (ABEs) can mediate two transition mutations, A-to-G and T-to-C, which are suitable for repairing G·C-to-T·A pathogenic variants, the most significant human pathogenic variant. By combining the protospacer adjacent motif (PAM)less SpRY nuclease with F148A-mutated TadA∗8e deaminase, we developed a new editor, SpRY-ABE8eF148A, in this study, which has narrowed the editing range and enhanced A-to-G editing efficiency in most sites with NR/YN PAMs. Furthermore, compared with SpRY-ABE8e, SpRY-ABE8eF148A significantly decreased the RNA off-target effect. Therefore, this engineered base editor, SpRY-ABE8eF148A, expanded the editing scope and improved the editing precision for G·C-to-T·A pathogenic variants. Besides, we established a bioinformatics tool, adenine base-repairing sgRNA database of pathogenic variant (ARDPM), to facilitate the development of precise editors.

Advances in transcriptomic technologies have deepened our understanding of the cellular gene expression programs of multicellular organisms and provided a theoretical basis for disease diagnosis and therapy. However, both bulk and single-cell RNA sequencing approaches lose the spatial context of cells within the tissue microenvironment, and the development of spatial transcriptomics has made overall bias-free access to both transcriptional information and spatial information possible. Here, we elaborate development of spatial transcriptomic technologies to help researchers select the best-suited technology for their goals and integrate the vast amounts of data to facilitate data accessibility and availability. Then, we marshal various computational approaches to analyze spatial transcriptomic data for various purposes and describe the spatial multimodal omics and its potential for application in tumor tissue. Finally, we provide a detailed discussion and outlook of the spatial transcriptomic technologies, data resources and analysis approaches to guide current and future research on spatial transcriptomics.

Strategies to improve the specificity of nuclease-based prime editor (PEn) are needed. Here the authors report a 53BP1-inhibitory ubiquitin variant-assisted PEn platform (uPEn) to inhibit NHEJ and enable precise prime editing for generation of insertions, deletions and replacements.

Abstract Distant metastasis is the main cause of mortality in breast cancer patients. Using the breast cancer genomic data from The Cancer Genome Atlas (TCGA), we identified brain specific Cav2.2 as a critical regulator of metastasis. Cav2.2 expression is significantly upregulated in breast cancer and its higher expression is inversely correlated with survival suggesting a previously unappreciated role of Cav2.2 in breast cancer. Cav2.2 is required for breast cancer migration, invasion, and metastasis. Interestingly, Cav2.2 promotes invadopodia formation and extracellular matrix (ECM) degradation through the stabilization of invadopodia component cortactin in a proteosome-dependent manner. Moreover, deubiquitinating enzyme USP43 mediated the functions of Cav2.2 in cortactin stabilization, invadopodia formation, ECM degradation, and metastasis. Interestingly, Cav2.2 upregulates USP43 expression through NFAT2 dephosphorylation and nuclear localization. Our study uncovered a novel pathway that regulates cortactin expression and invadopodia formation in breast cancer metastasis.

Genome editing in pluripotent stem cells (PSCs) using CRISPR technology holds great promise for therapeutic applications. Yet, it has been reported that Cas9-mediated cleavage could cause large deletions or rearrangements of DNA, and the selection of edited PSCs could acquire p53 mutations. Adenine base editors (ABEs) do not introduce DNA double-strand breaks and thus have been proposed as alternatives to circumvent those problems, but their off-target effects still limit their applications. Here, we tested different combinations of off-target reduction methods to further diminish off-target effects of ABEs without compromising their on-target editing efficiencies. We subsequently chose the best editor, CE-8e-dV, which contains V106W substitution, R153 deletion, and Cas-embedding strategy, to establish a single-cell-derived human embryonic stem cell (hESC) line expressing tetracycline-inducible CE-8e-dV. By performing RNA and whole-genome sequencing, we demonstrated that the expression of CE-8e-dV did not produce nearly any DNA or RNA off-target effects in hESCs. Our results provide stringent proof of the safety of ABEs in PSCs and suggest that CE-8e-dV could be suitable for related therapeutic strategies, such as generation of engineered stem cells in vitro and gene therapy in vivo.

Chemotherapy-related cognitive impairment (CRCI) or “chemo brain” is a devastating neurotoxic sequela of cancer-related treatments, especially for the elderly individuals. Here we show that PTPRO, a tyrosine phosphatase, is highly enriched in the hippocampus, and its level is tightly associated with neurocognitive function but declined significantly during aging. To understand the protective role of PTPRO in CRCI, a mouse model was generated by treating Ptpro–/– female mice with doxorubicin (DOX) because Ptpro–/– female mice are more vulnerable to DOX, showing cognitive impairments and neurodegeneration. By analyzing PTPRO substrates that are neurocognition-associated tyrosine kinases, we found that SRC and EPHA4 are highly phosphorylated/activated in the hippocampi of Ptpro–/– female mice, with increased sensitivity to DOX-induced CRCI. On the other hand, restoration of PTPRO in the hippocampal CA3 region significantly ameliorate CRCI in Ptpro–/– female mice. In addition, we found that the plant alkaloid berberine (BBR) is capable of ameliorating CRCI in aged female mice by upregulating hippocampal PTPRO. Mechanistically, BBR upregulates PTPRO by downregulating miR-25-3p, which directly targeted PTPRO. These findings collectively demonstrate the protective role of hippocampal PTPRO against CRCI.

New therapeutic strategies for the rapid and effective treatment of drug-resistant tuberculosis are highly desirable, and their development can be drastically accelerated by facile genetic manipulation methods in Mycobacterium tuberculosis (M. tuberculosis). Clustered regularly interspaced short palindromic repeat (CRISPR) base editors allow for rapid, robust, and programmed single-base substitutions and gene inactivation, yet no such systems are currently available in M. tuberculosis. By screening distinct CRISPR base editors, we discovered that only the unusual Streptococcus thermophilus CRISPR associated protein 9 (St1Cas9) cytosine base editor (CBE)—but not the widely used Streptococcus pyogenes Cas9 (SpCas9) or Lachnospiraceae bacterium Cpf1 (LbCpf1) CBEs—is active in mycobacteria. Despite the notable C-to-T conversions, a high proportion of undesired byproducts exists with St1Cas9 CBE. We therefore engineered St1Cas9 CBE by means of uracil DNA glycosylase inhibitor (UGI) or uracil DNA glycosylase (UNG) fusion, yielding two new base editors (CTBE and CGBE) capable of C-to-T or C-to-G conversions with dramatically enhanced editing product purity and multiplexed editing capacity in Mycobacterium smegmatis (M. smegmatis). Because wild-type St1Cas9 recognizes a relatively strict protospacer adjacent motif (PAM) sequence for DNA targeting, we engineered a PAM-expanded St1Cas9 variant by means of structure-guided protein engineering for the base editors, substantially broadening the targeting scope. We first developed and characterized CTBE and CGBE in M. smegmatis, and then applied CTBE for genome editing in M. tuberculosis. Our approaches significantly reduce the efforts and time needed for precise genetic manipulation and will facilitate functional genomics, antibiotic-resistant mechanism study, and drug-target exploration in M. tuberculosis and related organisms.

The evolution of epigenetic regulation of brain development in primates is not well understood. Here, the authors perform a comparative study of epigenetic dynamics of early prefrontal cortex development between human and rhesus macaque, finding divergent regulatory elements that may be related to cognitive capacity.

About 47% of pathogenic point mutations could be corrected by ABE-induced A·T-to-G·C conversions. However, the applications of ABEs are still hindered by undesired editing efficiency, limited editing scopes, and off-targeting effects. Here, we develop a new adenine base editor, by embedding TadA-8e monomer into SpRY-nCas9, named as CE-8e-SpRY, which exhibits higher activity at NRN than NYN PAMs favored by SpRY nuclease. CE-8e-SpRY could target nearly all genomic sites in principle and induces the highest targeting efficiency among tested SpRY-based ABEs. In addition, CE-8e-SpRY also shows reduced RNA and DNA off-targeting activities. With optimized sgRNAs, CE-8e-SpRY induces efficient or desired target editing at some disease-relevant loci where conventional ABEs were unable to induce precise and satisfied editing. Taken together, our CE-8e-SpRY could broaden the applicability of ABEs in correcting or introducing pathogenic point mutations.

Inborn errors of immunity (IEIs) are a group of inherited disorders caused by mutations in the protein-coding genes involved in innate and/or adaptive immunity. Hematopoietic stem cell transplantation (HSCT) is a mainstay definitive therapy for many severe IEIs. However, the lack of HLA-matched donors increases the risk of developing severe immunological complications. Gene therapy provides long-term clinical benefits and could be an attractive therapeutic strategy for IEIs. In this review, we describe the development and evolution of clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated proteins (Cas) gene-editing systems, including double-strand break (DSB)-based gene editing and DSB-free base editing or prime editing systems. Here, we discuss the advances in and issues associated with CRISPR/Cas gene editing tools and their potential as therapeutic alternatives for IEIs. We also highlight the progress of preclinical studies for the treatment of human genetic diseases, including IEIs, using CRISR/Cas and ongoing clinical trials based on this versatile technology.

Abstract Peroxisome proliferator-activated receptor (PPAR)-γ is a key transcription activator controlling adipogenesis and lipid metabolism. PPARγ binds PPAR response elements (PPREs) as the obligate heterodimer with retinoid X receptor (RXR) α, but exactly how PPARγ orchestrates the transcriptional response is unknown. This study demonstrates that PPARγ forms phase-separated droplets in vitro and solid-like nuclear condensates in cell, which is intriguingly mediated by its DNA binding domain characterized by the zinc finger motif. Furthermore, PPARγ forms nuclear condensates at PPREs sites through phase separation to compartmentalize its heterodimer partner RXRα to initiate PPARγ-specific transcriptional activation. Finally, using an optogenetic approach, the enforced formation of PPARγ/RXRα condensates leads to preferential enrichment at PPREs sites and significantly promotes the expression of PPARγ target genes. These results define a novel mechanism by which PPARγ engages the phase separation principles for efficient and specific transcriptional activation.

The prime editors (PEs) have shown great promise for precise genome modification. Here the authors place a stabilizing viral xrRNA motif to the 3′ of pegRNAs to enhance editing efficiencies.

Abstract CRISPR/RfxCas13d (CasRx) editing system can specifically and precisely cleave single-strand RNAs, which is a promising treatment for various disorders by downregulation of related gene expression. Here, we tested this RNA-editing approach on Beethoven (Bth) mice, an animal model for human DFNA36 due to a point mutation in Tmc1. We first screened 30 sgRNAs in cell cultures and found that CasRx with sgRNA3 reduced the Tmc1 Bth transcript by 90.8%, and the Tmc1 wild type transcript (Tmc1 + ) by 44.3%. We then injected a newly developed AAV vector (AAV-PHP.eB) based CasRx into the inner ears of neonatal Bth mice, and we found that Tmc1 Bth was reduced by 70.2% in 2 weeks with few off-target effects in the whole transcriptome. Consistently, we found improved hair cell survival, rescued hair bundle degeneration, and reduced mechanoelectrical transduction current. Importantly, the hearing performance, measured in both ABR and DPOAE thresholds, was improved significantly in all ages over 8 weeks. We, therefore, have validated the CRISPR/CasRx-based RNA editing strategy in treating autosomal-dominant hearing loss, paving way for its further application in many other hereditary diseases in hearing and beyond.

“Reinvigoration of antitumor immunity has recently become the central theme for the development of cancer therapies. Here the authors present an adaptable gene circuit to harness the CRISPRa for tumorlocalized immune activation.”

Interorganelle contacts and communications are increasingly recognized to play a vital role in cellular function and homeostasis. In particular, the mitochondria–endoplasmic reticulum (ER) membrane contact site (MAM) is known to regulate ion and lipid transfer, as well as signaling and organelle dynamics. However, the regulatory mechanisms of MAM formation and their function are still elusive. Here, we identify mitochondrial Lon protease (LonP1), a highly conserved mitochondrial matrix protease, as a new MAM tethering protein. The removal of LonP1 substantially reduces MAM formation and causes mitochondrial fragmentation. Furthermore, deletion of LonP1 in the cardiomyocytes of mouse heart impairs MAM integrity and mitochondrial fusion and activates the unfolded protein response within the ER (UPRER). Consequently, cardiac-specific LonP1 deficiency causes aberrant metabolic reprogramming and pathological heart remodeling. These findings demonstrate that LonP1 is a novel MAM-localized protein orchestrating MAM integrity, mitochondrial dynamics, and UPRER, offering exciting new insights into the potential therapeutic strategy for heart failure.

Modulating the extracellular matrix microenvironment is critical for achieving the desired macrophage phenotype in immune investigations or tumor therapy. Combining de novo protein design and biosynthesis techniques, herein, we designed a biomimetic polypeptide self-assembled nano-immunomodulator to trigger the activation of a specific macrophage phenotype. It was intended to be made up of (​GGS​GGP​GGG​PAS​AAA​NSA​SRA​TSN​SP)n, the RGD motif from collagen, and the IKVAV motif from laminin. The combination of these domains allows the biomimetic polypeptide to assemble into extracellular matrix-like nanofibrils, creating an extracellular matrix-like milieu for macrophages. Furthermore, changing the concentration further provides a facile route to fine-tune macrophage polarization, which enhances antitumor immune responses by precisely resetting tumor-associated macrophage immune responses into an M1-like phenotype, which is generally considered to be tumor-killing macrophages, primarily antitumor, and immune-promoting. Unlike metal or synthetic polymer-based nanoparticles, this polypeptide-based nanomaterial exhibits excellent biocompatibility, high efficacy, and precise tunability in immunomodulatory effectiveness. These encouraging findings motivate us to continue our research into cancer immunotherapy applications in the future.

Multi-nucleotide variants (MNVs) represent an important type of genetic variation and have biological and clinical significance. To simulate MNVs, we designed four dual-mutation base editors combining hA3A(Y130F), TadA8e(V106W), and protospacer adjacent motif (PAM)-flexible SpRY and selected cytosine and adenine base editor-SpRY (CABE-RY), which had the best editing performance, for further study. Characterization and comparison showed that CABE-RY had a smaller DNA editing window and lower RNA off-target edits than the corresponding single base editors. Thus, we have established a versatile tool to efficiently simulate MNVs over the genome, which could be very useful for functional studies on MNVs in humans.

Abstract N6-methyladenosine (m6A) is required for differentiation of human bone marrow mesenchymal stem cells (hBMSCs). However, its intrinsic mechanisms are largely unknown. To identify the possible role of m6A binding protein YTHDF1 in hBMSCs osteogenesis in vivo, we constructed Ythdf1 KO mice and showed that depletion of Ythdf1 would result in decreased bone mass in vivo. Both deletion of Ythdf1 in mouse BMSCs and shRNA-mediated knockdown of YTHDF1 in hBMSCs prevented osteogenic differentiation of cells in vitro. Using methylated RNA immunoprecipitation (Me-RIP) sequencing and RIP-sequencing, we found that ZNF839 (a zinc finger protein) served as a target of YTHDF1. We also verified its mouse homolog, Zfp839, was translationally regulated by Ythdf1 in an m6A-dependent manner. Zfp839 potentiated BMSC osteogenesis by interacting with and further enhancing the transcription activity of Runx2. These findings should improve our understanding of the mechanism of BMSC osteogenesis regulation and provide new ideas for the prevention and treatment of osteoporosis.

Prime editing enables efficient introduction of targeted transversions, insertions, and deletions in mammalian cells and several organisms. However, genetic disease models with base deletions by prime editing have not yet been reported in mice. Here, we successfully generate a mouse model with a cataract disorder through microinjection of prime editor 3 (PE3) plasmids to efficiently induce targeted single-base deletion. Notably, a generated mouse with a high G-deletion rate (38.2%) displays a nuclear cataract phenotype; the PE3-induced deletions in mutant mice achieve high rates of germline transmission to their progenies, with phenotypic inheritance of cataract. Our data propose that modeling a genetic disease with a single nucleotide deletion in mice can be achieved with prime genome editing in vivo.

Pathogenic mitochondrial DNA (mtDNA) mutations can cause a variety of human diseases. The recent development of genome-editing technologies to manipulate mtDNA, such as mitochondria-targeted DNA nucleases and base editors, offer a promising way for curing mitochondrial diseases caused by mtDNA mutations. The CRISPR-Cas9 system is a widely used tool for genome editing; however, its application in mtDNA editing is still under debate. In this study, we developed a mito-Cas9 system by adding the mitochondria-targeted sequences and 3′ untranslated region of nuclear-encoded mitochondrial genes upstream and downstream of the Cas9 gene, respectively. We confirmed that the mito-Cas9 system was transported into mitochondria and enabled knockin of exogenous single-stranded DNA oligonucleotides (ssODNs) into mtDNA based on proteinase and DNase protection assays. Successful knockin of exogenous ssODNs into mtDNA was further validated using polymerase chain reaction-free third-generation sequencing technology. We also demonstrated that RS-1, an agonist of RAD51, significantly increased knockin efficiency of the mito-Cas9 system. Collectively, we provide direct evidence that mtDNA can be edited using the CRISPR-Cas9 system. The mito-Cas9 system could be optimized as a promising approach for the treatment of mitochondrial diseases caused by pathogenic mtDNA mutations, especially those with homoplasmic mtDNA mutations.

Abstract Selective inhibition of targeted protein kinases is an effective therapeutic approach for treatment of human malignancies, which interferes phosphorylation of cellular substrates. However, a drug‐imposed selection creates pressures for tumor cells to acquire chemoresistance‐conferring mutations or activating alternative pathways, which can bypass the inhibitory effects of kinase inhibitors. Thus, identifying downstream phospho‐substrates conferring drug resistance is of great importance for developing poly‐pharmacological and targeted therapies. To identify functional phosphorylation sites involved in 5‐fluorouracil (5‐FU) resistance during its treatment of colorectal cancer cells, CRISPR‐mediated cytosine base editor (CBE) and adenine base editor (ABE) are utilized for functional screens by mutating phosphorylated amino acids with two libraries specifically targeting 7779 and 10 149 phosphorylation sites. Among the top enriched gRNAs‐induced gain‐of‐function mutants, the target genes are involved in cell cycle and post‐translational covalent modifications. Moreover, several substrates of RSK2 and PAK4 kinases are discovered as main effectors in responding to 5‐FU chemotherapy, and combinational treatment of colorectal cancer cells with 5‐FU and RSK2 inhibitor or PAK4 inhibitor can largely inhibit cell growth and enhance cell apoptosis through a RSK2/TP53BP1/γ‐H2AX phosphorylation signaling axis. It is proposed that this screen approach can be used for functional phosphoproteomics in chemotherapy of various human diseases.

Abstract RNA base editing is potential for cellular function research and genetic diseases treating. There are two main RNA base editors, REPAIR and RESCUE, for in vitro use. REPAIR was developed by fusing inactivated Cas13 (dCas13) with the adenine deaminase domain of ADAR2, which efficiently performs adenosine-to-inosine (A-to-I) RNA editing. RESCUE, which performs both cytidine-to-uridine (C-to-U) and A-to-I RNA editing, was developed by fusing inactivated Cas13 (dCas13) with the evolved ADAR2. However, the relatively low editing efficiency of the RESCUE system limits its broad application. Here, we constructed an enhanced RESCUE (eRESCUE) system; this dPspCas13b-RESCUE-NES system was generated by fusing inactivated PspCas13b with the evolved ADAR2. We determined the endogenous mRNA A-to-I and C-to-U editing efficiency mediated by the dPspCas13b-RESCUE-NES system in HEK-293T cells. This new RNA base editor was then used to induce 177Ser/Gly conversion of inhibitor kappa B kinase β (IKKβ) by changing the genetic code from AGU to GGU. The results showed that the eRESCUE editor mediates more efficient A-to-I and C-to-U RNA editing than the RESCUE RNA editor, as was previously reported. The 177Ser/Gly conversion of IKKβ, accomplished by converting the genetic code from AGU to GGU, resulted in a decrease in the phosphorylation of IKKβ and downregulation of downstream IKKβ-related genes. In summary, we developed a more efficient RNA base editor, eRESCUE, which may provide a useful tool for biomedical research and genetic disease treatment. Video Abstract

Abstract The currently available RESCUE RNA base editing system demonstrates considerable potential for the treatment of genetic diseases at the transcriptional level. However, the relatively high incidence of off-target events hampers the precise RNA editing, thereby limiting its use in the clinical setting. This study describes a new RNA base editing method, named ecRESCUE, which utilizes inducible stabilization of the protein ecDHFR DD fused at the C-terminal of the original RESCUE system. In vitro experiments in 293T cells showed that the ecRESCUE editor markedly reduced the incidence of off-target single nucleotide polymorphisms without affecting the RNA A-to-I and C-to-U base editing efficiency. Altogether, these results demonstrate that the inducible ecRESCUE system represents an attractive approach to regulate and improve the outcome of the available RNA base editor with reduced off-targeting activity. Video Abstract

Base editors can induce transcriptome-wide RNA off-target editing independent of gRNA. Here, the authors engineer ABEmax variants with minimized RNA off-target activities.

Abstract Background Site-specific C>T DNA base editing has been achieved by recruiting cytidine deaminases to the target C using catalytically impaired Cas proteins; the target C is typically located within 5-nt editing window specified by the guide RNAs. The prototypical cytidine base editor BE3, comprising rat APOBEC1 (rA1) fused to nCas9, can indiscriminately deaminate multiple C’s within the editing window and also create substantial off-target edits on the transcriptome. A powerful countermeasure for the DNA off-target editing is to replace rA1 with APOBEC proteins which selectively edit C’s in the context of specific motifs, as illustrated in eA3A-BE3 which targets TC. However, analogous editors selective for other motifs have not been described. In particular, it has been challenging to target a particular C in C-rich sequences. Here, we sought to confront this challenge and also to overcome the RNA off-target effects seen in BE3. Results By replacing rA1 with an optimized human A3G (oA3G), we developed oA3G-BE3, which selectively targets CC and CCC and is also free of global off-target effects on the transcriptome. Furthermore, we created oA3G-BE4max, an upgraded version of oA3G-BE3 with robust on-target editing. Finally, we showed that oA3G-BE4max has negligible Cas9-independent off-target effects at the genome. Conclusions oA3G-BE4max can edit C(C)C with high efficiency and selectivity, which complements eA3A-editors to broaden the collective editing scope of motif selective editors, thus filling a void in the base editing tool box.

Activation of human immune T-cells by swine leukocyte antigens class I (SLA-I) and class II (SLA-II) leads to xenograft destruction. Here, we generated the GGTA1, B2M, and CIITA (GBC) triple-gene-modified Diannan miniature pigs, analyzed the transcriptome of GBC-modified peripheral blood mononuclear cells (PBMCs) in the pig's spleen, and investigated their effectiveness in anti-immunological rejection. A total of six cloned piglets were successfully generated using somatic cell nuclear transfer, one of them carrying the heterozygous mutations in triple genes and the other five piglets carrying the homozygous mutations in GGTA1 and CIITA genes, but have the heterozygous mutation in the B2M gene. The autopsy of GBC-modified pigs revealed that a lot of spot bleeding in the kidney, severe suppuration and necrosis in the lungs, enlarged peripulmonary lymph nodes, and adhesion between the lungs and chest wall were found. Phenotyping data showed that the mRNA expressions of triple genes and protein expressions of B2M and CIITA genes were still detectable and comparable with wild-type (WT) pigs in multiple tissues, but α1,3-galactosyltransferase was eliminated, SLA-I was significantly decreased, and four subtypes of SLA-II were absent in GBC-modified pigs. In addition, even in swine umbilical vein endothelial cells (SUVEC) induced by recombinant porcine interferon gamma (IFN-γ), the expression of SLA-I in GBC-modified pig was lower than that in WT pigs. Similarly, the expression of SLA-II DR and DQ also cannot be induced by recombinant porcine IFN-γ. Through RNA sequencing (RNA-seq), 150 differentially expressed genes were identified in the PBMCs of the pig's spleen, and most of them were involved in immune- and infection-relevant pathways that include antigen processing and presentation and viral myocarditis, resulting in the pigs with GBC modification being susceptible to pathogenic microorganism. Furthermore, the numbers of human IgM binding to the fibroblast cells of GBC-modified pigs were obviously reduced. The GBC-modified porcine PBMCs triggered the weaker proliferation of human PBMCs than WT PBMCs. These findings indicated that the absence of the expression of α1,3-galactosyltransferase and SLA-II and the downregulation of SLA-I enhanced the ability of immunological tolerance in pig-to-human xenotransplantation.

DNA base editors can display off-target effects on DNA and RNA. Here the authors embed the base editing enzymes in the middle of nCas9 to reduce these without impacting on-target editing.

Abstract Base editing has the potential to improve important economic traits in agriculture and can precisely convert single nucleotides in DNA or RNA sequences into minimal double-strand DNA breaks (DSB). Adenine base editors (ABE) have recently emerged as a base editing tool for the conversion of targeted A:T to G:C, but have not yet been used in sheep. ABEmax is one of the latest versions of ABE, which consists of a catalytically-impaired nuclease and a laboratory-evolved DNA-adenosine deaminase. The Booroola fecundity (FecB B ) mutation (g.A746G, p.Q249R) in the bone morphogenetic protein receptor 1B (BMPR1B) gene influences fecundity in many sheep breeds. In this study, by using ABEmax we successfully obtained lambs with defined point mutations that result in an amino acid substitution (p.Gln249Arg). The efficiency of the defined point mutations was 75% in newborn lambs, since six lambs were heterozygous at the FecB B mutation site (g.A746G, p.Q249R), and two lambs were wild-type. We did not detect off-target mutations in the eight edited lambs. Here, we report the validation of the first gene-edited sheep generated by ABE and highlight its potential to improve economically important traits in livestock.

Until now, the transcriptome of preimplantation mouse embryos has only been analysed by short-read sequencing. Here, the authors perform long-read sequencing to provide a more detailed transcriptome of the preimplantation mouse embryo, identifying various novel transcripts, for example Kdm4dl.

ABSTRACTIdeal methods for detecting pathogens should be sensitive, specific, rapid, cost-effective and instrument-free. Conventional nucleic acid pathogen detection strategies, mostly PCR-based techniques, have various limitations, such as expensive equipment, reagents and skilled performance. Recently, CRISPR/Cas-based methods have burst onto the scene, with the potential to power the pathogen detection field. Here we introduce these unique methods and discuss its hurdles and promises.

Abstract Combinatorial antibody libraries not only effectively reduce antibody discovery to a numbers game, but enable documentation of the history of antibody responses in an individual. The severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) pandemic has prompted a wider application of this technology to meet the public health challenge of pandemic threats in the modern era. Herein, a combinatorial human antibody library constructed 20 years before the coronavirus disease 2019 (COVID‐19) pandemic is used to discover three highly potent antibodies that selectively bind SARS‐CoV‐2 spike protein and neutralize authentic SARS‐CoV‐2 virus. Compared to neutralizing antibodies from COVID‐19 patients with generally low somatic hypermutation (SHM), these three antibodies contain over 13–22 SHMs, many of which are involved in specific interactions in their crystal structures with SARS‐CoV‐2 spike receptor binding domain. The identification of these somatically mutated antibodies in a pre‐pandemic library raises intriguing questions about the origin and evolution of these antibodies with respect to their reactivity with SARS‐CoV‐2.

Drug-resistant tuberculosis (TB) is a serious public health problem and threat to global TB prevention and control. Streptomycin (STR) is the earliest and classical anti-TB drug, and it is the earliest drug that generated resistance to anti-TB treatment, which limits its use in treating TB and impedes TB control efforts. The rapid, economical, and highly sensitive detection of STR-resistant TB may help reduce disease transmission and morbimortality. CRISPR/CRISPR-associated protein (Cas) is a new-generation pathogen detection method that can detect single-nucleotide polymorphisms with high sensitivity and good specificity. In this study, a Cas12a RR detection system that can recognize more non-traditional protospacer-adjacent motif-targeting sequences was developed based on Cas12a combined with recombinase polymerase amplification technology. This system detects 0.1% of the target substance, and the entire detection process can be completed within 60 min. Its sensitivity and specificity for detecting clinical STR-resistant Mycobacterium tuberculosis were both 100%. Overall, the Cas12 RR detection system provides a novel alternative for the rapid, simple, sensitive, and specific detection of STR-resistant TB, which may contribute to the prompt treatment and prevention of disease transmission in STR-resistant TB.

Rapid and sensitive nucleic acid detection of SARS-CoV-2 has contributed to the clinical diagnosis and control of COVID-19. Although detection of virus genomic RNA (gRNA) has been commonly used in clinical diagnosis, SARS-CoV-2 gRNA detection could not discriminate between active infectious virus with remnant viral RNA. In contrast to genomic RNA, subgenomic RNAs (sgRNAs) are only produced when the virus is actively replicating and transcription, detection of sgRNA could be an indication to evaluate infectivity. CRISPR/Cas-based nucleic acid detection methods have been considered potential diagnostic tools due to their intrinsic sensitivity, specificity and simplicity. In this study, to specifically detect active virus replication, we developed a CRISPR-based active SARS-CoV-2 (CRISPR-actCoV) detection strategy by detecting sgRNAs of SARS-CoV-2. CRISPR-actCoV with CRISPR Cas12a-assisted fluorescence reporter system enables detection of sgRNAs at 10 copies in 35 min with high specificity and can be read out with naked eyes. Further, we performed CRISPR-actCoV mediated sgRNA detection in 30 SARS-CoV-2 potentially infected clinical samples, and 21 samples were SARS-CoV-2 sgRNA positive. A quantitative RT-PCR assay was also performed to detect gRNA of SARS-CoV-2 in parallel. Among the 30 clinical samples, 27 samples were gRNA positive. Taken together, CRISPR-actCoV provides an alternative for rapid and accurate detection of active SARS-CoV-2 and has great significance in better response of coronavirus causing epidemic disease.

Genome editing technology holds great promise for genome manipulation and gene therapy. While widespread utilization, genome editing has been used to unravel the roles of specific genes in differentiation and pluripotency of stem cells, and reinforce the stem cell-based applications. In this review, we summarize the advances of genome editing technology, as well as the derivative technologies from CRISPR/Cas system, which show tremendous potential in various fields. We also highlight the key findings in the studies of stem cells and regeneration by genome editing technology. Keywords: Genome editing, CRISPR/Cas9, Gene therapy, Stem cell

Sensitive and efficient detection of drug-resistant mutations is essential in cancer precision medicine. In treating acute myeloid leukemia (AML), FLT3 gene F691L mutation shows universal resistance to all currently available FLT3 inhibitors. However, there is no particular detection method for FLT3-F691L. Commonly-used first-generation sequencing (FGS) approaches have low sensitivity, and next-generation sequencing (NGS) is time-consuming. Herein, we developed an accurate and sensitive FLT3-F691L diagnostic method by CRISPR detection. Briefly, the FLT3-691 region is amplified by recombinase polymerase amplification (RPA) and detected by L691-crRNA induced Cas12a reaction, and finally the result can be directly observed under a blue lamp or analyzed by a fluorescence reader. Confirmed by the tests on diluted plasmids and 120 AML patient samples, this method can achieve a sensitivity of 0.1% and complete the whole diagnosis process within 40 min. Potentially, this method will play an important role in point-of-care applications and guidance of AML treatment.

Abstract Background Dynamic N 6-methyladenosine (m6A) modification was previously identified as a ubiquitous post-transcriptional regulation that affected mRNA homeostasis. However, the m6A-related epitranscriptomic alterations and functions remain elusive in human cancer. Here we aim to identify the profile and outcome of m6A-methylation in hepatocellular carcinoma (HCC). Results Using liquid chromatography-tandem mass spectrometry and m6A-immunoprecipitation in combination with high-throughput sequencing, we determined the m6A-mRNA levels in human HCC. Human HCC exhibited a characteristic gain of m6A modification in tandem with an increase of mRNA expression, owing to YTH domain family 2 (YTHDF2) reduction. The latter predicted poor classification and prognosis of HCC patients, and highly correlated with HCC m6A landscape. YTHDF2 silenced in human HCC cells or ablated in mouse hepatocytes provoked inflammation, vascular reconstruction and metastatic progression. Mechanistically, YTHDF2 processed the decay of m6A-containing interleukin 11 (IL11) and serpin family E member 2 (SERPINE2) mRNAs, which were responsible for the inflammation-mediated malignancy and disruption of vascular normalization. Reciprocally, YTHDF2 transcription succumbed to hypoxia-inducible factor-2α (HIF-2α). Administration of a HIF-2α antagonist (PT2385) restored YTHDF2-programed epigenetic machinery and repressed liver cancer. Conclusion Our results have characterized the m6A-mRNA landscape in human HCC and revealed YTHDF2 as a molecular ‘rheostat’ in epitranscriptome and cancer progression.

Abstract Background Catalytic defect Cas9‐cytosine deaminase fusion is widely used in base editing. The Multiple copy numbers of the MS2 binding site (MBS) can recruit multiple MS2 coat proteins (MCPs), which are usually applied to amplify signals. Our study aimed to apply the MS2 signal amplification system to the base editing system in order to achieve simultaneous mutations of multiple bases at the target genome site. Methods Multiple copy numbers of the MS2 were ligated to the 3′‐end of sgRNA, and MCP was fused to the 5′‐end of cytosine deaminases. The MS2 was recognized by MCP to recruit cytosine deaminase for base substitutions (C‐T) at the target site. Different Cas9 variants, different cytosine deaminases and different copy numbers of MS2 were tested in this system, and the different versions of base editors were compared by editing efficiency and window. Results In this study, dCas9, nCas9 (D10A) and nCas9 (H840A) were used. Among these 3 Cas9 variants, dCas9 exhibited higher base mutation efficiency. Two cytosine deaminases were then applied and the efficiency of rAPOBEC1 deaminase was found to be higher than AID. We also increased the copy numbers of MS2 linked to sgRNA from 2 to 12. Disappointingly, the sgRNA‐12x MS2 did not improve the editing efficiency or increase the editing window. Conclusion An optimal version of base editor based on the MS2 system, MS2‐BE‐rAPOBEC1 (sgRNA‐2x MS2, MCP‐rAPOBEC1 and dCas9), was obtained. This tool can simultaneously mutate multiple bases at the target site, providing a new approach for the study of genome functions.

Base editing systems show their power in modeling and correcting the pathogenic mutations of genetic diseases. Previous studies have already demonstrated the editing efficiency of BE3-mediated C-to-T conversion in human embryos. However, the precision and efficiency of a recently developed adenine base editor (ABE), which converts A-to-G editing in human embryos, remain to be addressed. Here we selected reported pathogenic mutations to characterize the ABE in human tripronuclear embryos. We found effective A-to-G editing occurred at the desirable sites using the ABE system. Furthermore, ABE-mediated A-to-G editing in the single blastomere of the edited embryos exhibited high product purity. By deep sequencing and whole-genome sequencing, A or T mutations didn’t increase significantly, and no off-target or insertion or deletion (indel) mutations were detected in these edited embryos, indicating the ABE-mediated base editing in human embryos is precise and controllable. For some sites, since a different editing pattern was obtained from the cells and the embryos targeted with the same single guide RNA (sgRNA), it suggests that ABE-mediated editing might have different specificity in vivo. Taken together, we efficiently generated pathogenic A-to-G mutations in human tripronuclear embryos via ABE-mediated base editing.

The development of CRISPR/Cas9-mediated base editors (BEs) provided a versatile tool for precise genome editing. The recently developed xCas9-derived base editors (xBEs) that recognize the NG PAM substantially expand the targeting scope in the genome, while their editing efficiency needs to be improved. Here, we described an improved version of xBEs by fusing the BPNLS and Gam to the N terminus of xBEs (BPNLS-Gam-xBE3 and BPNLS-xABE), and this version of base editor displayed higher targeting efficiency for the majority of detected sites. By using this improved version of xBEs, we successfully created and corrected pathogenic mutations at genomic sites with the NGN protospacer-adjacent motif in human cells. Lastly, we used BPNLS-Gam-xBE3 to model pathogenic mutations in discarded human tripronuclear (3PN) zygotes, and no obvious off-targets and indels were detected. Taken together, the data in our study offer an efficient tool for precise genome editing and, thus, an enriched base editing toolkit. Keywords: CRISPR/Cas, base editor, xCas9, base editing efficiency, pathogenic mutation, Wilson disease