CRISPR Journal最新文献

Custom CRISPR screens are powerful tools for rapid, hypothesis-driven discovery, but their design is often complex and time-consuming. Green Listed v2.0 simplifies this process with an intuitive workflow for designing custom CRISPR spacer libraries and supports downstream analysis for all users, irrespective of their computational experience. The web application features a user-friendly graphical interface freely accessible at https://greenlisted.cmm.se. Version 2.0 includes significant upgrades to the original 2016 version that were implemented based on user feedback. This includes a new gene synonym tool, expanded library options, optimized output lists, performance improvements, and linked scripts for the rational design of custom CRISPR screen gene sets.

CRISPR-Cas9 genome editing holds tremendous potential for accelerating genetic improvements in aquaculture. The success of the CRISPR-Cas9 system relies on the specificity and efficiency of engineered single-guide RNAs (sgRNAs). In this study, we optimized an in vitro validation protocol for sgRNAs to streamline the gene editing process, capitalizing on the limited breeding season of the Pacific oyster (Crassostrea gigas). We evaluated the efficiency of 11 sgRNAs targeting four genes both in vitro and in vivo in C. gigas. In addition, we found that Cas9 protein differs from Cas9 mRNA in gene editing efficiency at various stages of early development. Cas9 protein proved particular efficacy in achieving early and efficient gene knockout, functioning effectively during the first cell division and facilitating biallelic gene knockouts. Statistical analysis showed that in the protein group, the biallelic editing frequency ranged from 12.5% to 57.8%, and the overall editing frequency reached as high as 75-90.6%. The mRNA group exhibited a biallelic editing frequency of 3.1-14.0% and the overall editing frequency spanning 65.6-78.1%. Contrary to expectations, low-temperature incubation (20°C) of oyster embryos prolonged the time window for the first cell division but did not improve gene editing efficiency, likely due to the high temperature sensitivity of Cas9 enzyme activity. Together, this study provides a comprehensive analysis of factors affecting the efficiency of CRISPR-Cas9 gene editing in C. gigas, providing a robust framework for future gene editing endeavors in mollusks and other marine invertebrates.

Bacteria and archaea acquire resistance to genetic parasites by preferentially integrating short fragments of foreign DNA at one end of a Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR). "Leader" DNA upstream of CRISPR loci regulates transcription and foreign DNA integration into the CRISPR. Here, we analyze 37,477 CRISPRs from 39,277 bacterial and 556 archaeal genomes to identify conserved sequence motifs in CRISPR leaders. A global analysis of all leader sequences fails to identify universally conserved motifs. However, an analysis of leader sequences that have been grouped by 16S rRNA-based taxonomy and CRISPR subtype reveals 87 specific motifs in type I, II, III, and V CRISPR leaders. Fourteen of these leader motifs have biochemically demonstrated roles in CRISPR biology including integration, transcription, and CRISPR RNA processing. Another 28 motifs are related to DNA binding sites for proteins with functions that are consistent with regulating CRISPR activity. In addition, we show that these leader motifs can be used to improve existing CRISPR detection methods and enhance the accuracy of CRISPR classification.

Type V CRISPR systems are highly diverse in sequence, mechanism, and function. Although recent efforts have greatly expanded our understanding of their evolution, the diversity of type V systems remains to be completely explored, and many clades have not been experimentally characterized. In this work, we mined metagenomic databases to identify three new subtypes and nine new variants of Cas12, the effector of Type V systems, and provide experimental and computational characterization of their Protospacer-Adjacent Motif (PAM), interference activity, loci architecture, and tracrRNA dependence. Half of the new Cas12s are found in phages or prophages. New subtypes Cas12o and Cas12p lack the canonical RuvC catalytic residues, suggesting they interfere with the target without cleavage, possibly by blocking transcription or replication. One variant, Cas12f10, displays substantial activity on PAM-less targets. Our work expands the diversity of the functionally characterized Cas12 effectors and provides some promising candidates for genome engineering tools.

CRISPR gene editing is a cutting-edge technology that has advanced tremendously in recent years. The first clinical CRISPR applications have been approved, and more gene editing therapies are to be expected in human medicine. Consequently, continuous basic research is needed to assess possibilities and prime future clinical applications. Because this technology not only offers new possibilities for treating diseases but also raises important ethical and societal questions, collaboration between human, life, biomedical, and medical sciences is needed. In this article, we discuss the practical challenges of such interdisciplinary projects and present strategies for addressing them based on our experience of conducting an interdisciplinary project on CRISPR. This work aims to help and encourage interdisciplinary collaborations and discussions on modern scientific endeavors that, such as gene editing, tend to blur the lines between traditional disciplines. The strategies suggested include realistic expectations, shared goals, space setting, and expert and lay dialogue.

The incorporation of nuclear localization signal (NLS) sequences at one or both termini of CRISPR enzymes is a widely adopted strategy to facilitate genome editing. Engineered variants of CRISPR enzymes with diverse NLS sequences have demonstrated superior performance, promoting nuclear localization and efficient DNA editing. However, limiting NLS fusion to the CRISPR protein's termini can negatively impact protein yield via recombinant expression. Here we present a distinct strategy involving the installation of hairpin internal NLS sequences (hiNLS) at rationally selected sites within the backbone of CRISPR-Cas9. We evaluated the performance of these hiNLS Cas9 variants by editing genes in human primary T cells following the delivery of ribonucleoprotein enzymes via either electroporation or co-incubation with amphiphilic peptides. We show that hiNLS Cas9 variants can improve editing efficiency in T cells compared with constructs with terminally fused NLS sequences. Furthermore, many hiNLS Cas9 constructs can be produced with high purity and yield, even when these constructs contain as many as nine NLS. These hiNLS Cas9 constructs represent a key advance in optimizing CRISPR effector design and may contribute to improved editing outcomes in research and therapeutic applications.

The silkworm (Bombyx mori) is a lepidopteran model insect that has been utilized for basic research and industrial applications. In this species, transcription activator-like effector nucleases (TALENs) have been found to function efficiently, and we previously developed a TALEN-mediated genome editing system for knockout and knock-in experiments using plasmids and single-stranded oligodeoxynucleotides (ssODNs) as donors. By contrast, clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9)-mediated genome editing, especially for gene integration, remains limited. In this study, we attempted to improve CRISPR-Cas systems to expand the utility of genome editing in the silkworm. Codon optimization of Cas9 improved genome editing efficiency, and single-guide RNA utilization also resulted in a higher genome editing efficiency than crRNA/tracrRNA when Cas9 messenger RNA (mRNA) was used. CRISPR-Cas12a-mediated genome editing and targeted sequence integration using ssODNs were both successfully performed. Overall, our study provides a robust technical platform that can facilitate basic and applied silkworm studies.

Cas9 must be localized to the nucleus to access the genome of mammalian cells. For most proteins, adding a single nuclear localization signal (NLS) is sufficient to promote nuclear entry. However, Cas9 nuclear entry appears to be inefficient as multiple NLSs are typically added to Cas9. Here, we found that three different Cas9 variants interact with the ribosome in HEK293T cells, and that this interaction is RNA mediated. Following immunoprecipitation-mass spectrometry of cytoplasmic-localized Cas9-0NLS and nuclear-localized Cas9-4NLS constructs, we identified novel Cas9 interactors in postmitotic neurons, including KEAP1 and additional ribosomal subunits, the latter were enriched in Cas9-0NLS samples. Collectively, our results suggest that Cas9 is sequestered in the cytoplasm of mammalian cells, in part, via interaction with the ribosome. Increasing the number of NLSs on Cas9 and/or increasing the amount of cytoplasmic guide RNA has the potential to outcompete ribosomal RNA binding and promote efficient nuclear localization of CRISPR-Cas9 variants.

Design of guide RNA (gRNA) with high efficiency and specificity is vital for successful application of the CRISPR gene editing technology. Although many machine learning (ML) and deep learning (DL)-based tools have been developed to predict gRNA activities, a systematic and unbiased evaluation of their predictive performance is still needed. Here, we provide a brief overview of in silico tools for CRISPR design and assess the CRISPR datasets and statistical metrics used for evaluating model performance. We benchmark seven ML and DL-based CRISPR-Cas9 editing efficiency prediction tools across nine CRISPR datasets covering six cell types and three species. The DL models CRISPRon and DeepHF outperform the other models exhibiting greater accuracy and higher Spearman correlation coefficient across multiple datasets. We compile all CRISPR datasets and in silico prediction tools into a GuideNet resource web portal, aiming to facilitate and streamline the sharing of CRISPR datasets. Furthermore, we summarize features affecting CRISPR gene editing activity, providing important insights into model performance and the further development of more accurate CRISPR prediction models.