Type III CRISPR-Cas Systems: Deciphering the Most Complex Prokaryotic Immune System

CRISPR applications in microbial World: Assessing the opportunities and challenges

Genome editing has emerged during the past few decades in the scientific research area to manipulate genetic composition, obtain desired traits, and deal with biological challenges by exploring genetic traits and their sequences at a level of precision. The discovery of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) as a genome editing tool has offered a much better understanding of cellular and molecular mechanisms. This technology emerges as one of the most promising candidates for genome editing, offering several advantages over other techniques such as high accuracy and specificity. In the microbial world, CRISPR/Cas technology enables researchers to manipulate the genetic makeup of micro-organisms, allowing them to achieve almost impossible tasks. This technology initially discovered as a bacterial defense mechanism, is now being used for gene cutting and editing to explore more of its dimensions. CRISPR/Cas 9 systems are highly efficient and flexible, leading to its widespread uses in microbial research areas. Although this technology is widely used in the scientific community, many challenges, including off-target activity, low efficiency of Homology Directed Repair (HDR), and ethical considerations, still need to be overcome before it can be widely used. As CRISPR/Cas technology has revolutionized the field of microbiology, this review article aimed to present a comprehensive overview highlighting a brief history, basic mechanisms, and its application in the microbial world along with accessing the opportunities and challenges.

Selective degradation of phage RNAs by the Csm6 ribonuclease provides robust type III CRISPR immunity in Streptococcus thermophilus

Type III CRISPR immune systems bind viral or plasmid RNA transcripts and activate Csm3/Cmr4 and Cas10 nucleases to uniquely cleave both invader RNA and DNA, respectively. Additionally, type III effector complexes generate cyclic oligoadenylate (cOA) signaling molecules to activate trans-acting, auxiliary Csm6/Csx1 ribonucleases, previously proposed to be non-specific in their in vivo RNA cleavage preference. Despite extensive in vitro studies, the nuclease requirements of type III systems in their native contexts remain poorly understood. Here we systematically investigated the in vivo roles for immunity of each of the three Streptococcus thermophilus (Sth) type III-A Cas nucleases and cOA signaling by challenging nuclease defective mutant strains with plasmid and phage infections. Our results reveal that RNA cleavage by Csm6 is both sufficient and essential for maintaining wild-type levels of immunity. Importantly, Csm6 RNase activity leads to immunity against even high levels of phage challenge without causing host cell dormancy or death. Transcriptomic analyses during phage infection indicated Csm6-mediated and crRNA-directed preferential cleavage of phage transcripts. Our findings highlight the critical role of Csm6 RNase activity in type III immunity and demonstrate specificity for invader RNA transcripts by Csm6 to ensure host cell survival upon phage infection.

Targeting mRNA-coding genes in prostate cancer using CRISPR/Cas9 technology with a special focus on androgen receptor signaling

BACKGROUND

Prostate cancer is among prevalent cancers in men. Numerous strategies have been proposed to intervene with the important prostate cancer-related signaling pathways. Among the most promising strategies is CRISPR/Cas9 strategy. This strategy has been used to modify expression of a number of genes in prostate cancer cells.

AIMS

This review summarizes the most recent progresses in the application of CRISPR/Cas9 strategy in modification of prostate cancer-related phenotypes with an especial focus on pathways related to androgen receptor signaling.

CONCLUSION

CRISPR/Cas9 technology has successfully targeted several genes in the prostate cancer cells. Moreover, the efficiency of this technique in reducing tumor burden has been tested in animal models of prostate cancer. Most of targeted genes have been related with the androgen receptor signaling. Targeted modulation of these genes have affected growth of castration-resistant prostate cancer. PI3K/AKT/mTOR signaling and immune response-related genes have been other targets that have been successfully modulated by CRISPR/Cas9 technology in prostate cancer. Based on the rapid translation of this technology into the clinical application, it is anticipated that novel treatments based on this technique change the outcome of this malignancy in future.

CRISPR RNA binding drives structural ordering that primes Cas7-11 for target cleavage

Type III-E CRISPR-Cas effectors, of which Cas7-11 is the first, are single proteins that cleave target RNAs without nonspecific collateral cleavage, opening new possibilities for RNA editing. Biochemical experiments combined with amide hydrogen-deuterium exchange (HDX-MS) experiments provide a first glimpse of the conformational dynamics of apo Cas7-11. HDX-MS revealed the backbone comprised of the four Cas7 zinc-binding RRM folds are well-folded but insertion sequences are highly dynamic and fold upon binding crRNA. The crRNA causes folding of disordered catalytic loops and β-hairpins, stronger interactions at domain-domain interfaces, and folding of the Cas7.1 processing site. Target RNA binding causes only minor ordering around the catalytic loops of Cas7.2 and Cas7.3. We show that Cas7-11 cannot fully process the CRISPR array and that binding of partially processed crRNA induces multiple states in Cas7-11 and reduces target RNA cleavage. The insertion domain shows the most ordering upon binding of mature crRNA. Finally, we show a crRNA-induced conformational change in one of the TPR-CHAT binding sites providing an explanation for why crRNA binding facilitates TPR-CHAT binding. The results provide the first glimpse of the apo state of Cas7-11 and reveal how its structure and function are regulated by crRNA binding.

Ecological and evolutionary dynamics of CRISPR-Cas systems in Clostridium botulinum: Insights from genome mining and comparative analysis

Understanding the prevalence and distribution of CRISPR-Cas systems across different strains can illuminate the ecological and evolutionary dynamics of Clostridium botulinum populations. In this study, we conducted genome mining to characterize the CRISPR-Cas systems of C. botulinum strains. Our analysis involved retrieving complete genome sequences of these strains and assessing the diversity, prevalence, and evolution of their CRISPR-Cas systems. Subsequently, we performed an analysis of homology in spacer sequences from identified CRISPR arrays to investigate and characterize the range of targeted phages and plasmids. Additionally, we investigated the evolutionary trajectory of C. botulinum strains under selective pressures from foreign invasive DNA. Our findings revealed that 306 strains possessed complete CRISPR-Cas structures, comprising 58% of the studied C. botulinum strains. Secondary structure prediction of consensus repeats indicated that subtype II-C, with longer stems compared to subtypes ID and IB, tended to form more stable RNA secondary structures. Moreover, protospacer motif analysis demonstrated that strains with subtype IB CRISPR-Cas systems exhibited 5'-CGG-3', 5'-CC-3', and 5'-CAT-3' motifs in the 3' flanking regions of protospacers. The diversity observed in CRISPR-Cas systems indicated their classification into subtypes IB, ID, II-C, III-B, and III-D. Furthermore, our results showed that systems with subtype ID and III-D frequently harbored similar spacer patterns. Moreover, analysis of spacer sequences homology with phage and prophage genomes highlighted the specific activities exhibited by subtype IB and III-B against phages and plasmids, providing valuable insights into the functional specialization within these systems.

Characterization of Ligilactobacillus salivarius CRISPR-Cas systems

Ligilactobacillus is a diverse genus among lactobacilli with phenotypes that reflect adaptation to various hosts. CRISPR-Cas systems are highly prevalent within lactobacilli, and Ligilactobacillus salivarius, the most abundant species of Ligilactobacillus, possesses both DNA- and RNA-targeting CRISPR-Cas systems. In this study, we explore the presence and functional properties of I-B, I-C, I-E, II-A, and III-A CRISPR-Cas systems in over 500 Ligilactobacillus genomes, emphasizing systems found in L. salivarius. We examined the I-E, II-A, and III-A CRISPR-Cas systems of two L. salivarius strains and observed occurrences of split cas genes and differences in CRISPR RNA maturation in native hosts. This prompted testing of the single Cas9 and multiprotein Cascade and Csm CRISPR-Cas effector complexes in a cell-free context to demonstrate the functionality of these systems. We also predicted self-targeting spacers within L. salivarius CRISPR-Cas systems and found that nearly a third of L. salivarius genomes possess unique self-targeting spacers that generally target elements other than prophages. With these two L. salivarius strains, we performed prophage induction coupled with RNA sequencing and discovered that the prophages residing within these strains are inducible and likely active elements, despite targeting by CRISPR-Cas systems. These findings deepen our comprehension of CRISPR-Cas systems in L. salivarius, further elucidating their relationship with associated prophages and providing a functional basis for the repurposing of these Cas effectors for bacterial manipulation.

IMPORTANCE

Ligilactobacillus salivarius is a diverse bacterial species widely used in the food and dietary supplement industries. In this study, we investigate the occurrence and diversity of their adaptive immune systems, CRISPR-Cas, in over 500 genomes. We establish their function and provide insights into their role in the interplay between the bacterial host and the predatory phages that infect them. Such findings expand our knowledge about these important CRISPR-Cas immune systems widespread across the bacterial tree of life and also provide a technical basis for the repurposing of these molecular machines for the development of molecular biology tools and the manipulation and engineering of bacteria and other life forms.

Interference Requirements of Type III CRISPR-Cas Systems from Thermus thermophilus

Among the diverse prokaryotic adaptive immunity mechanisms, the Type III CRISPR-Cas systems are the most complex. The multisubunit Type III effectors recognize RNA targets complementary to CRISPR RNAs (crRNAs). Target recognition causes synthesis of cyclic oligoadenylates that activate downstream auxiliary effectors, which affect cell physiology in complex and poorly understood ways. Here, we studied the ability of III-A and III-B CRISPR-Cas subtypes from Thermus thermophilus to interfere with plasmid transformation. We find that for both systems, requirements for crRNA-target complementarity sufficient for interference depend on the target transcript abundance, with more abundant targets requiring shorter complementarity segments. This result and thermodynamic calculations indicate that Type III effectors bind their targets in a simple bimolecular reaction with more extensive crRNA-target base pairing compensating for lower target abundance. Since the targeted RNA used in our work is non-essential for either the host or the plasmid, the results also establish that a certain number of target-bound effector complexes must be present in the cell to interfere with plasmid establishment. For the more active III-A system, we determine the minimal length of RNA-duplex sufficient for interference and show that the position of this minimal duplex can vary within the effector. Finally, we show that the III-A immunity is dependent on the HD nuclease domain of the Cas10 subunit. Since this domain is absent from the III-B system the result implies that the T. thermophilus III-B system must elicit a more efficient cyclic oligoadenylate-dependent response to provide the immunity.

The structural biology of type III CRISPR-Cas systems

CRISPR-Cas system is an RNA-guided adaptive immune system widespread in bacteria and archaea. Among them, type III CRISPR-Cas systems are the most ancient throughout the CRISPR-Cas family, proving anti-phage defense through a crRNA-guided RNA targeting manner and possessing multiple enzymatic activities. Type III CRISPR-Cas systems comprise four typical members (type III-A to III-D) and two atypical members (type III-E and type III-F), providing immune defense through distinct mechanisms. Here, we delve into structural studies conducted on three well-characterized members: the type III-A, III-B, and III-E systems, provide an overview of the structural insights into the crRNA-guided target RNA cleavage, self/non-self discrimination, and the target RNA-dependent regulation of enzymatic subunits in the effector complex.

The influence of the copy number of invader on the fate of bacterial host cells in the antiviral defense by CRISPR-Cas10 DNases

Type III CRISPR-Cas10 systems employ multiple immune activities to defend their hosts against invasion from mobile genetic elements (MGEs), including DNase and cyclic oligoadenylates (cOA) synthesis both of which are hosted by the type-specific protein Cas10. Extensive investigations conducted for the activation of Cas accessory proteins by cOAs have revealed their functions in the type III immunity, but the function of the Cas10 DNase in the same process remains elusive. Here, Lactobacillus delbrueckii subsp. Bulgaricus type III-A (Ld) Csm system, a type III CRISPR system that solely relies on its Cas10 DNase for providing immunity, was employed as a model to investigate the DNase function. Interference assay was conducted in Escherichia coli using two plasmids: pCas carrying the LdCsm system and pTarget producing target RNAs. The former functioned as a de facto "CRISPR host element" while the latter, mimicking an invading MGE. We found that, upon induction of immune responses, the fate of each genetic element was determined by their copy numbers: plasmid of a low copy number was selectively eliminated from the E. coli cells regardless whether it represents a de facto CRISPR host or an invader. Together, we reveal, for the first time, that the immune mechanisms of Cas10 DNases are of two folds: the DNase activity is capable of removing low-copy invaders from infected cells, but it also leads to abortive infection when the invader copy number is high.

Bacteriophage strategies for overcoming host antiviral immunity

Phages and their bacterial hosts together constitute a vast and diverse ecosystem. Facing the infection of phages, prokaryotes have evolved a wide range of antiviral mechanisms, and phages in turn have adopted multiple tactics to circumvent or subvert these mechanisms to survive. An in-depth investigation into the interaction between phages and bacteria not only provides new insight into the ancient coevolutionary conflict between them but also produces precision biotechnological tools based on anti-phage systems. Moreover, a more complete understanding of their interaction is also critical for the phage-based antibacterial measures. Compared to the bacterial antiviral mechanisms, studies into counter-defense strategies adopted by phages have been a little slow, but have also achieved important advances in recent years. In this review, we highlight the numerous intracellular immune systems of bacteria as well as the countermeasures employed by phages, with an emphasis on the bacteriophage strategies in response to host antiviral immunity.

Characteristics of subtype III-A CRISPR-Cas system in Mycobacterium tuberculosis: An overview

CRISPR-Cas systems are the only RNA- guided adaptive immunity pathways that trigger the detection and destruction of invasive phages and plasmids in bacteria and archaea. Due to its prevalence and mystery, the Class 1 CRISPR-Cas system has lately been the subject of several studies. This review highlights the specificity of CRISPR-Cas system III-A in Mycobacterium tuberculosis, the tuberculosis-causing pathogen, for over twenty years. We discuss the difference between the several subtypes of Type III and their defence mechanisms. The anti-CRISPRs (Acrs) recently described, the critical role of Reverse transcriptase (RT) and housekeeping nuclease for type III CRISPR-Cas systems, and the use of this cutting-edge technology, its impact on the search for novel anti-tuberculosis drugs.

Functional and Phylogenetic Diversity of Cas10 Proteins

Cas10 proteins are large subunits of type III CRISPR RNA (crRNA)-guided surveillance complexes, many of which have nuclease and cyclase activities. Here, we use computational and phylogenetic methods to identify and analyze 2014 Cas10 sequences from genomic and metagenomic databases. Cas10 proteins cluster into five distinct clades that mirror previously established CRISPR-Cas subtypes. Most Cas10 proteins (85.0%) have conserved polymerase active-site motifs, while HD-nuclease domains are less well conserved (36.0%). We identify Cas10 variants that are split over multiple genes or genetically fused to nucleases activated by cyclic nucleotides (i.e., NucC) or components of toxin-antitoxin systems (i.e., AbiEii). To clarify the functional diversification of Cas10 proteins, we cloned, expressed, and purified five representatives from three phylogenetically distinct clades. None of the Cas10s are functional cyclases in isolation, and activity assays performed with polymerase domain active site mutants indicate that previously reported Cas10 DNA-polymerase activity may be a result of contamination. Collectively, this work helps clarify the phylogenetic and functional diversity of Cas10 proteins in type III CRISPR systems.

Anti-CRISPR Discovery: Using Magnets to Find Needles in Haystacks

CRISPR-Cas immune systems in bacteria and archaea protect against viral infection, which has spurred viruses to develop dedicated inhibitors of these systems called anti-CRISPRs (Acrs). Like most host-virus arms races, many diverse examples of these immune and counter-immune proteins are encoded by the genomes of bacteria, archaea, and their viruses. For the case of Acrs, it is almost certain that just a small minority of nature's true diversity has been described. In this review, I discuss the various approaches used to identify these Acrs and speculate on the future for Acr discovery. Because Acrs can determine infection outcomes in nature and regulate CRISPR-Cas activities in applied settings, they have a dual importance to both host-virus conflicts and emerging biotechnologies. Thus, revealing the largely hidden world of Acrs should provide important lessons in microbiology that have the potential to ripple far beyond the field.

AlphaFold2 and its applications in the fields of biology and medicine

AlphaFold2 (AF2) is an artificial intelligence (AI) system developed by DeepMind that can predict three-dimensional (3D) structures of proteins from amino acid sequences with atomic-level accuracy. Protein structure prediction is one of the most challenging problems in computational biology and chemistry, and has puzzled scientists for 50 years. The advent of AF2 presents an unprecedented progress in protein structure prediction and has attracted much attention. Subsequent release of structures of more than 200 million proteins predicted by AF2 further aroused great enthusiasm in the science community, especially in the fields of biology and medicine. AF2 is thought to have a significant impact on structural biology and research areas that need protein structure information, such as drug discovery, protein design, prediction of protein function, et al. Though the time is not long since AF2 was developed, there are already quite a few application studies of AF2 in the fields of biology and medicine, with many of them having preliminarily proved the potential of AF2. To better understand AF2 and promote its applications, we will in this article summarize the principle and system architecture of AF2 as well as the recipe of its success, and particularly focus on reviewing its applications in the fields of biology and medicine. Limitations of current AF2 prediction will also be discussed.

Importance of mobile genetic element immunity in numerically abundant Trichodesmium clades

The colony-forming cyanobacteria Trichodesmium spp. are considered one of the most important nitrogen-fixing genera in the warm, low nutrient ocean. Despite this central biogeochemical role, many questions about their evolution, physiology, and trophic interactions remain unanswered. To address these questions, we describe Trichodesmium pangenomic potential via significantly improved genomic assemblies from two isolates and 15 new >50% complete Trichodesmium metagenome-assembled genomes from hand-picked, Trichodesmium colonies spanning the Atlantic Ocean. Phylogenomics identified ~four N2 fixing clades of Trichodesmium across the transect, with T. thiebautii dominating the colony-specific reads. Pangenomic analyses showed that all T. thiebautii MAGs are enriched in COG defense mechanisms and encode a vertically inherited Type III-B Clustered Regularly Interspaced Short Palindromic Repeats and associated protein-based immunity system (CRISPR-Cas). Surprisingly, this CRISPR-Cas system was absent in all T. erythraeum genomes, vertically inherited by T. thiebautii, and correlated with increased signatures of horizontal gene transfer. Additionally, the system was expressed in metaproteomic and transcriptomic datasets and CRISPR spacer sequences with 100% identical hits to field-assembled, putative phage genome fragments were identified. While the currently CO2-limited T. erythraeum is expected to be a 'winner' of anthropogenic climate change, their genomic dearth of known phage resistance mechanisms, compared to T. thiebautii, could put this outcome in question. Thus, the clear demarcation of T. thiebautii maintaining CRISPR-Cas systems, while T. erythraeum does not, identifies Trichodesmium as an ecologically important CRISPR-Cas model system, and highlights the need for more research on phage-Trichodesmium interactions.

CRISPR-Based Approaches for Cancer Immunotherapy

Clustered regularly interspaced short palindromic repeats (CRISPR) technology is a powerful gene editing tool that has the potential to revolutionize cancer treatment. It allows for precise and efficient editing of specific genes that drive cancer growth and progression. CRISPR-based approaches gene knock-out, which deletes specific genes or sequences of DNA within a cancer cell, and gene knock-in, which inserts new sequences of DNA into a cancer cell to identify potential targets for cancer therapy. Further, genome-wide CRISPR-Cas9-based screens identify specific markers for diagnosis of cancers. Recently, immunotherapy has become a highly efficient strategy for the treatment of cancer. The use of CRISPR in cancer immunotherapy is focused on enhancing the function of T cells, making them more effective at attacking cancer cells and inactivating the immune evasion mechanisms of cancer cells. It has the potential to generate CAR-T cells, which are T cells that have been genetically engineered to target and attack cancer cells specifically. This review uncovers the latest developments in CRISPR-based gene editing strategies and delivery of their components in cancer cells. In addition, the applications of CRISPR in cancer immune therapy are discussed. Overall, this review helps to explore the potential of CRISPR-based strategies in cancer immune therapy in clinical settings.

Molecular Details of DNA Integration by CRISPR-Associated Proteins During Adaptation in Bacteria and Archaea

Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) proteins constitute an adaptive immune system in bacteria and archaea, where immunological memory is retained in the CRISPR locus as short pieces of the intruding nucleic acid, termed spacers. The adaptation to new infections occurs through the integration of a new spacer into the CRISPR array. For immune protection, spacers are transcribed into CRISPR RNAs (crRNA) that are used to guide the effector nuclease of the system in sequence-dependent target cleavage. Spacers originate as a prespacer from either DNA or RNA depending on the CRISPR-Cas system being observed, and the nearly universal Cas proteins, Cas1 and Cas2, insert the prespacer into the CRISPR locus during adaptation in all systems that contain them. The mechanism of site-specific prespacer integration varies across CRISPR classes and types, and distinct differences can even be found within the same subtype. In this review, the current knowledge on the mechanisms of prespacer integration in type II-A CRISPR-Cas systems will be described. Comparisons of the currently characterized type II-A systems show that distinct mechanisms exist within different members of this subtype and are correlated to sequence-specific interactions of Cas proteins and the DNA elements present in the CRISPR array. These observations indicate that nature has fine-tuned the mechanistic details while performing the basic step of DNA integration by Cas proteins, which offers unique advantages to develop Cas1-Cas2-based biotechnology.

CRISPR-Cas13: A new technology for the rapid detection of pathogenic microorganisms

Pathogenic microorganisms have major impacts on human lives. Rapid and sensitive diagnostic tools are urgently needed to facilitate the early treatment of microbial infections and the effective control of microbial transmission. CRISPR-Cas13 employs programmable RNA to produce a sensitive and specific method with high base resolution and thus to provide a novel tool for the rapid detection of microorganisms. The review aims to provide insights to spur further development by summarizing the characteristics of effectors of the CRISPR-Cas13 system and by describing the latest research into its application in the rapid detection of pathogenic microorganisms in combination with nucleic acid extraction, isothermal amplification, and product detection.

Investigating CRISPR spacer targets and their impact on genomic diversification of Streptococcus mutans

CRISPR-Cas is a bacterial immune system that restricts the acquisition of mobile DNA elements. These systems provide immunity against foreign DNA by encoding CRISPR spacers that help target DNA if it re-enters the cell. In this way, CRISPR spacers are a type of molecular tape recorder of foreign DNA encountered by the host microorganism. Here, we extracted ∼8,000 CRISPR spacers from a collection of over three hundred Streptococcus mutans genomes. Phage DNA is a major target of S. mutans spacers. S. mutans strains have also generated immunity against mobile DNA elements such as plasmids and integrative and conjugative elements. There may also be considerable immunity generated against bacterial DNA, although the relative contribution of self-targeting versus bona fide intra- or inter-species targeting needs to be investigated further. While there was clear evidence that these systems have acquired immunity against foreign DNA, there appeared to be minimal impact on horizontal gene transfer (HGT) constraints on a species-level. There was little or no impact on genome size, GC content and ‘openness’ of the pangenome when comparing between S. mutans strains with low or high CRISPR spacer loads. In summary, while there is evidence of CRISPR spacer acquisition against self and foreign DNA, CRISPR-Cas does not act as a barrier on the expansion of the S. mutans accessory genome.

Dali server: structural unification of protein families

Protein structure is key to understanding biological function. Structure comparison deciphers deep phylogenies, providing insight into functional conservation and functional shifts during evolution. Until recently, structural coverage of the protein universe was limited by the cost and labour involved in experimental structure determination. Recent breakthroughs in deep learning revolutionized structural bioinformatics by providing accurate structural models of numerous protein families for which no structural information existed. The Dali server for 3D protein structure comparison is widely used by crystallographers to relate new structures to pre-existing ones. Here, we report two most recent upgrades to the web server: (i) the foldomes of key organisms in the AlphaFold Database (version 1) are searchable by Dali, (ii) structural alignments are annotated with protein families. Using these new features, we discovered a novel functionally diverse subgroup within the WRKY/GCM1 clan. This was accomplished by linking the structurally characterized SWI/SNF and NAM families as well as the structural models of the CG-1 family and uncharacterized proteins to the structure of Gti1/Pac2, a previously known member of the WRKY/GCM1 clan. The Dali server is available at http://ekhidna2.biocenter.helsinki.fi/dali. This website is free and open to all users and there is no login requirement.

Development of clustered regularly interspaced short palindromic repeats/CRISPR-associated technology for potential clinical applications

The clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) proteins constitute the innate adaptive immune system in several bacteria and archaea. This immune system helps them in resisting the invasion of phages and foreign DNA by providing sequence-specific acquired immunity. Owing to the numerous advantages such as ease of use, low cost, high efficiency, good accuracy, and a diverse range of applications, the CRISPR-Cas system has become the most widely used genome editing technology. Hence, the advent of the CRISPR/Cas technology highlights a tremendous potential in clinical diagnosis and could become a powerful asset for modern medicine. This study reviews the recently reported application platforms for screening, diagnosis, and treatment of different diseases based on CRISPR/Cas systems. The limitations, current challenges, and future prospectus are summarized; this article would be a valuable reference for future genome-editing practices.