Precise Regulation of Cas9-Mediated Genome Engineering by Anti-CRISPR-Based Inducible CRISPR Controllers

CRISPR/Cas9 technology for advancements in cancer immunotherapy: from uncovering regulatory mechanisms to therapeutic applications

In recent years, immunotherapy has developed rapidly as a new field of tumour therapy. However, the efficacy of tumour immunotherapy is not satisfactory due to the immune evasion mechanism of tumour cells, induction of immunosuppressive tumour microenvironment (TME), and reduction of antigen delivery, etc. CRISPR/Cas9 gene editing technology can accurately modify immune and tumour cells in tumours, and improve the efficacy of immunotherapy by targeting immune checkpoint molecules and immune regulatory genes, which has led to the great development and application. In current clinical trials, there are still many obstacles to the application of CRISPR/Cas9 in tumour immunotherapy, such as ensuring the accuracy and safety of gene editing, overcoming overreactive immune responses, and solving the challenges of in vivo drug delivery. Here we provide a systematic review on the application of CRISPR/Cas9 in tumour therapy to address the above existing problems. We focus on CRISPR/Cas9 screening and identification of immunomodulatory genes, targeting of immune checkpoint molecules, manipulation of immunomodulators, enhancement of tumour-specific antigen presentation and modulation of immune cell function. Second, we also highlight preclinical studies of CRISPR/Cas9 in animal models and various delivery systems, and evaluate the efficacy and safety of CRISPR/Cas9 technology in tumour immunotherapy. Finally, potential synergistic approaches for combining CRISPR/Cas9 knockdown with other immunotherapies are presented. This study underscores the transformative potential of CRISPR/Cas9 to reshape the landscape of tumour immunotherapy and provide insights into novel therapeutic strategies for cancer patients.

Recent Advancements in Reducing the Off-Target Effect of CRISPR-Cas9 Genome Editing

The CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)) and the associated protein (Cas9) system, a young but well-studied genome-editing tool, holds plausible solutions to a wide range of genetic disorders. The single-guide RNA (sgRNA) with a 20-base user-defined spacer sequence and the Cas9 endonuclease form the core of the CRISPR-Cas9 system. This sgRNA can direct the Cas9 nuclease to any genomic region that includes a protospacer adjacent motif (PAM) just downstream and matches the spacer sequence. The current challenge in the clinical applications of CRISPR-Cas9 genome-editing technology is the potential off-target effects that can cause DNA cleavage at the incorrect sites. Off-target genome editing confuses and diminishes the therapeutic potential of CRISPR-Cas9 in addition to potentially casting doubt on scientific findings regarding the activities of genes. In this review, we summarize the recent technological advancements in reducing the off-target effect of CRISPR-Cas9 genome editing.

Fine-Tuning the Epigenetic Landscape: Chemical Modulation of Epigenome Editors

Epigenome editing has emerged as a powerful technique for targeted manipulation of the chromatin and transcriptional landscape, employing designer DNA binding domains fused with effector domains, known as epi-editors. However, the constitutive expression of dCas9-based epi-editors presents challenges, including off-target activity and lack of temporal resolution. Recent advancements of dCas9-based epi-editors have addressed these limitations by introducing innovative switch systems that enable temporal control of their activity. These systems allow precise modulation of gene expression over time and offer a means to deactivate epi-editors, thereby reducing off-target effects associated with prolonged expression. The development of novel dCas9 effectors regulated by exogenous chemical signals has revolutionized temporal control in epigenome editing, significantly expanding the researcher's toolbox. Here, we provide a comprehensive review of the current state of these cutting-edge systems and specifically discuss their advantages and limitations, offering context to better understand their capabilities.

Anti-CRISPR Proteins and Their Application to Control CRISPR Effectors in Mammalian Systems

CRISPR-Cas effectors are powerful tools for genome and transcriptome targeting and editing. Naturally, these protein-RNA complexes are part of the microbial innate immune system, which emerged from the evolutionary arms race between microbes and phages. This coevolution has also given rise to so-called anti-CRISPR (Acr) proteins that counteract the CRISPR-Cas adaptive immunity. Acrs constitutively block cognate CRISPR-Cas effectors, e.g., by interfering with guide RNA binding, target DNA/RNA recognition, or target cleavage. In addition to their important role in microbiology and evolution, Acrs have recently gained particular attention for being useful tools and switches to regulate or fine-tune the activity of CRISPR-Cas effectors. Due to their commonly small size, high inhibition potency, and structural and mechanistic versatility, Acrs offer a wide range of potential applications for controlling CRISPR effectors in heterologous systems, including mammalian cells.Here, we review the diverse applications of Acrs in mammalian cells and organisms and discuss the underlying engineering strategies. These applications include (i) persistent blockage of CRISPR-Cas function to create write-protected cells, (ii) reduction of CRISPR-Cas off-target editing, (iii) focusing CRISPR-Cas activity to specific cell types and tissues, (iv) spatiotemporal control of CRISPR effectors based on engineered, opto-, or chemogenetic Acrs, and (v) the use of Acrs for selective binding and detection of CRISPR-Cas effectors in complex samples. We will also highlight potential future applications of Acrs in a biomedical context and point out present challenges that need to be overcome on the way.

Inflammation conditional genome editing mediated by the CRISPR-Cas9 system

The specificity of CRISPR-Cas9 in response to particular pathological stimuli remains largely unexplored. Hence, we designed an inflammation-inducible CRISPR-Cas9 system by grafting a sequence that binds with NF-κB to the CRISPR-Cas9 framework, termed NBS-CRISPR. The genetic scissor function of this developed genome-editing tool is activated on encountering an inflammatory attack and is inactivated or minimized in non-inflammation conditions. Furthermore, we employed this platform to reverse inflammatory conditions by targeting the MyD88 gene, a crucial player in the NF-κB signaling pathway, and achieved impressive therapeutic effects. Finally, during inflammation, P65 (RELA) can translocate to the nucleus from the cytoplasm. Herein, to avoid Cas9 leaky DNA cleavage activity i, we constructed an NBS-P65-CRISPR system expressing the Cas9-p65 fusion protein. Our inflammation inducible Cas9-mediated genome editing strategy provides new perspectives and avenues for pathological gene interrogation.

Applications of Anti-CRISPR Proteins in Genome Editing and Biotechnology

In the ten years since the discovery of the first anti-CRISPR (Acr) proteins, the number of validated Acrs has expanded rapidly, as has our understanding of the diverse mechanisms they employ to suppress natural CRISPR-Cas immunity. Many, though not all, function via direct, specific interaction with Cas protein effectors. The abilities of Acr proteins to modulate the activities and properties of CRISPR-Cas effectors have been exploited for an ever-increasing spectrum of biotechnological uses, most of which involve the establishment of control over genome editing systems. This control can be used to minimize off-target editing, restrict editing based on spatial, temporal, or conditional cues, limit the spread of gene drive systems, and select for genome-edited bacteriophages. Anti-CRISPRs have also been developed to overcome bacterial immunity, facilitate viral vector production, control synthetic gene circuits, and other purposes. The impressive and ever-growing diversity of Acr inhibitory mechanisms will continue to allow the tailored applications of Acrs.

Research and Therapeutic Approaches in Stem Cell Genome Editing by CRISPR Toolkit

The most widely used genome editing toolkit is CRISPR (clustered regularly interspaced short palindromic repeats). It provides the possibility of replacing and modifying DNA and RNA nucleotides. Furthermore, with advancements in biological technology, inhibition and activation of the transcription of specific gene(s) has become possible. Bioinformatics tools that target the evolution of CRISPR-associated protein 9 (Cas9) turn this protein into a vehicle that is specific for a DNA or RNA region with single guide RNA (sgRNA). This toolkit could be used by researchers to investigate the function of stem cell gene(s). Here, in this review article, we cover recent developments and applications of this technique in stem cells for research and clinical purposes and discuss different CRISPR/Cas technologies for knock-out, knock-in, activation, or inhibition of gene expression. Additionally, a comparison of several deliveries and off-target detecting strategies is discussed.

Controlling CRISPR-Cas9 by guide RNA engineering

The clustered regularly interspaced short palindromic repeats (CRISPR) system is a product of million years of evolution by microbes to fight against invading genetic materials. Around 10 years ago, scientists started to repurpose the CRISPR as genetic tools by molecular engineering approaches. The guide RNA provides a versatile and unique platform for the innovation to improve and expand the application of CRISPR-Cas9 system. In this review, we will first introduce the basic sequence and structure of guide RNA and its role during the function of CRISPR-Cas9. We will then summarize recent progress on the development of various guide RNA engineering strategies. These strategies have been dedicated to improve the performance of CRISPR-Cas9, to achieve precise spatiotemporal control of CRISPR-Cas9, and to broaden the application of CRISPR-Cas9. Finally, we will briefly discuss the uniqueness and advantage of guide RNA-engineering based systems versus those with engineered Cas9 proteins and speculate potential future directions in guide RNA engineering. This article is categorized under: RNA Methods > RNA Analyses In Vitro and In Silico RNA Methods > RNA Nanotechnology Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.

Small Molecules for Enhancing the Precision and Safety of Genome Editing

Clustered regularly interspaced short palindromic repeats (CRISPR)-based genome-editing technologies have revolutionized biology, biotechnology, and medicine, and have spurred the development of new therapeutic modalities. However, there remain several barriers to the safe use of CRISPR technologies, such as unintended off-target DNA cleavages. Small molecules are important resources to solve these problems, given their facile delivery and fast action to enable temporal control of the CRISPR systems. Here, we provide a comprehensive overview of small molecules that can precisely modulate CRISPR-associated (Cas) nucleases and guide RNAs (gRNAs). We also discuss the small-molecule control of emerging genome editors (e.g., base editors) and anti-CRISPR proteins. These molecules could be used for the precise investigation of biological systems and the development of safer therapeutic modalities.

CRISPR-Cas technology a new era in genomic engineering

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CRISPR-Cas systems offer a flexible and easy-to-use molecular platform to precisely modify and control organisms' genomes in a variety of fields, from agricultural biotechnology to therapeutics.

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With CRISPR technology, crop genomes can be precisely edited in a shorter and more efficient approach compared to traditional breeding or classic mutagenesis.

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CRISPR-Cas system can be used to manage the fermentation process by addressing phage resistance, antimicrobial activity, and genome editing.

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CRISPR-Cas technology has opened up a new era in gene therapy and other therapeutic fields and given hope to thousands of patients with genetic diseases.

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Anti-CRISPR molecules are powerful tools for regulating the CRISPR-Cas systems.

The CRISPR-Cas systems have offered a flexible, easy-to-use platform to precisely modify and control the genomes of organisms in various fields, ranging from agricultural biotechnology to therapeutics. This system is extensively used in the study of infectious, progressive, and life-threatening genetic diseases for the improvement of quality and quantity of major crops and in the development of sustainable methods for the generation of biofuels. As CRISPR-Cas technology continues to evolve, it is becoming more controllable and precise with the addition of molecular regulators, which will provide benefits for everyone and save many lives. Studies on the constant growth of CRISPR technology are important due to its rapid development. In this paper, we present the current applications and progress of CRISPR-Cas genome editing systems in several fields of research, we further highlight the applications of anti-CRISPR molecules to regulate CRISPR-Cas gene editing systems, and we discuss ethical considerations in CRISPR-Cas applications.