Search Results (42)

Leptospirosis is a globally distributed zoonotic disease caused by pathogenic bacteria of the Leptospira genus. Genome editing in Leptospira has been difficult to perform. Currently, the functionality of the CRISPR-Cas system has been demonstrated in species such as Leptospira interrogans. However, the different CRISPR-Cas systems present in most of the 77 species are unknown. Therefore, the objective of this study was to identify these arrays across the genomes of all described Leptospira species using bioinformatics tools. Methods: a bioinformatics workflow was followed: genomes were downloaded from the NCBI database; Cas protein detection was carried out using the CRISPR-CasFinder and RAST web servers; functional analyses of Cas proteins were performed with InterProScan, ProtParam, Swiss Model, Alphafold3, Swiss PDB Viewer, and Pymol; conservation pattern detection was conducted using MEGA12, and Seqlogos; spacer identification was carried out with the Actinobacteriophages database and BLAST version 1.4.0; and bacteriophage detection was performed using PHASTER, and PHASTEST. Results: Cas proteins were detected in 36 out of the 77 species of the Leptospira species, including Cas1 to Cas9 and Cas12. These proteins were classified into Class 1 and Class 2 systems, corresponding to types I, II, and V. Direct repeats and spacers were detected in 19 species, with the direct repeats exhibiting two conserved nucleotide motifs. Analysis of spacer sequences revealed 323 distinct bacteriophages. Additionally, three intact bacteriophages were detected in the genomes of four Leptospira species. Notably, two saprophytic species have complete CRISPR-Cas systems. Conclusions: The presence of Cas proteins, direct repeats, and spacer sequences with homology to bacteriophage genomes provides evidence for a functional CRISPR-Cas system in at least 19 species. Full article

Senecavirus A (SVA) is an emerging pathogen responsible for vesicular lesions and neonatal mortality in swine. In the absence of effective vaccines or therapeutics, early and accurate diagnosis is essential for controlling SVA outbreaks. Although nucleic acid-based detection methods are commonly employed, there remains a pressing need for rapid, convenient, highly sensitive, and specific diagnostic tools. Here, we developed a two-pot assay combining recombinase polymerase amplification (RPA) with CRISPR/Cas12a containing crRNA targeting canonical protospacer adjacent motifs (PAMs) for simple, rapid, and visual identification of SVA in clinical samples. Subsequently, we successfully streamlined this system into a one-pot assay by selecting a specially designed crRNA targeting suboptimal PAM and integrating RPA amplification reagents and CRISPR/Cas12a detection components into a single reaction system in one tube. The developed methods exhibited diagnostic specificity, showing no cross-reactivity with four major swine viruses, while showing remarkable sensitivity with a lower detection limit of just two copies. Clinical validation in field samples using these two methods revealed perfect agreement (100% concordance) with conventional quantitative PCR (qPCR) results (sample size, n = 28), with both assays completing detection within 30 min. These results demonstrate that both the one-pot and two-pot RPA-CRISPR/Cas12a assays offer a reliable and efficient method for detecting SVA in this pilot study. Despite the limited sample size, the assays combine rapid reaction time with high sensitivity and specificity, showing great potential for future diagnostic applications. Full article

A straightforward approach is suggested to selectively recognize specific products of loop-mediated isothermal amplification (LAMP) with the Cas12a nuclease without a need for a protospacer adjacent motif (PAM) in the sequence of LAMP amplicons (LAMPlicons). This strategy is based on the presence of single-stranded DNA loops in LAMPlicons and the ability of Cas12a to be trans-activated via the binding of guide RNA (gRNA) to single-stranded DNA in the absence of PAM. The approach feasibility is demonstrated on Clavibacter species—multiple bacterial plant pathogens that cause harmful diseases in agriculturally important plants. For Clavibacter species, the detection sensitivity of the developed PAM-independent LAMP/Cas12a system was determined by that of LAMP. The overall detection selectivity was enhanced by the Cas12a analysis of LAMPlicons. It was shown that the LAMP/Cas12a detection system can be fine-tuned by carefully designing gRNA to selectively distinguish C. sepedonicus from other Clavibacter species based on single nucleotide substitutions in the targeted LAMPlicon loop. The suggested loop-based Cas12a analysis of LAMPlicons was compatible with the format of a single test tube assay with the option of naked-eye detection. The findings broaden the palette of approaches to designing PAM-independent LAMP/Cas12a detection systems with potential for on-site testing. Full article

The recent discovery of TIGR-Tas (Tandem Interspaced Guide RNA-Targeting Systems) marks a major advance in the field of genome editing, introducing a new class of compact, programmable DNA-targeting systems that function independently of traditional CRISPR-Cas pathways. TIGR-Tas effectors use a novel dual-spacer guide RNA (tigRNA) to recognize both strands of target DNA without requiring a protospacer adjacent motif (PAM). These Tas proteins introduce double-stranded DNA cuts with characteristic 8-nucleotide 3′ overhangs and are significantly smaller than Cas9, offering delivery advantages for in vivo editing. Structural analyses reveal homology to box C/D snoRNP proteins, suggesting a previously unrecognized evolutionary lineage of RNA-guided nucleases. This review positions TIGR-Tas at the forefront of a new wave of RNA-programmable genome-editing technologies. In parallel, I provide comparative insight into the diverse and increasingly modular CRISPR-Cas systems, including Cas9, Cas12, Cas13, and emerging effectors like Cas3, Cas10, CasΦ, and Cas14. While the CRISPR-Cas universe has revolutionized molecular biology, TIGR-Tas systems open a complementary and potentially more versatile path for programmable genome manipulation. I discuss mechanistic distinctions, evolutionary implications, and potential applications in human cells, synthetic biology, and therapeutic genome engineering. Full article

High-sensitivity and high-specificity biodetection is critical for advancing applications in life sciences, biosafety, food safety, and environmental monitoring. CRISPR/Cas systems have emerged as transformative tools in biosensing due to their unparalleled specificity, programmability, and unique enzymatic activities. They exhibit two key cleavage behaviors: precise ON-target cleavage guided by specific protospacers, which ensures accurate target recognition, and bystander cleavage activity triggered upon target binding, which enables robust signal amplification. These properties make CRISPR/Cas systems highly versatile for designing biosensors for ultra-sensitive detection. This review comprehensively explores recent advancements in CRISPR/Cas system-based biosensors, highlighting their impact on improving biosensing performance. We discuss the integration of CRISPR/Cas systems with diverse signal readout mechanisms, including electrochemical, fluorescent, colorimetric, surface-enhanced Raman scattering (SERS), and so on. Additionally, we examine the development of integrated biosensing systems, such as microfluidic devices and portable biosensors, which leverage CRISPR/Cas technology for point-of-care testing (POCT) and high-throughput analysis. Furthermore, we identify unresolved challenges, aiming to inspire innovative solutions and accelerate the translation of these technologies into practical applications for diagnostics, food, and environment safety. Full article

Background/Objectives: CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats)-associated protein 9 is now widely used in agriculture and medicine. Off-target effects can lead to unexpected results that may be harmful, and these effects are a common concern in both research and therapeutic applications. Methods: In this study, using pineapple as the gene-editing material, eighteen target sequences with varying numbers of PAM (Protospacer-Adjacent Motif) sites were used to construct gRNA vectors. Fifty mutant lines were generated for each target sequence, and the off-target rates were counted. Results: Selecting sequences with multiple flanking PAM sites as editing targets resulted in a lower off-target rate compared to those with a single PAM site. Target sequences with two 5′-NGG (“N” represents any nucleobase, followed by two guanine “G”) PAM sites at the 3′ end exhibited greater specificity and a higher probability of binding with the Cas9 protein than those only with one 5′-NGG PAM site at the 3′ end. Conversely, although the target sequence with a 5′-NAG PAM site (where “N” is any nucleobase, followed by adenine “A” and guanine “G”) adjacent and upstream of an NGG PAM site had a lower off-target rate compared to sequences with only an NGG PAM site, their off-target rates were still higher than those of sequences with two adjacent 5′-NAG PAM sites. Among the target sequences of pineapple mutant lines (AcACS1, AcOT5, AcCSPE6, AcPKG11A), more deletions than insertions were found. Conclusions: We found that target sequences with multiple flanking PAM sites are more likely to bind with the Cas9 protein and induce mutations. Selecting sequences with multiple flanking PAM sites as editing targets can reduce the off-target effects of the Cas9 enzyme in pineapple. These findings provide a foundation for improving off-target prediction and engineering CRISPR-Cas9 complexes for gene editing. Full article

The non-ideal accuracy and insufficient selectivity of CRISPR/Cas9 systems is a serious problem for their use as a genome editing tool. It is important to select the target sequence correctly so that the CRISPR/Cas9 system does not cut similar sequences. This requires an understanding of how and why mismatches in the target sequence can affect the efficiency of the Cas9/sgRNA complex. In this work, we studied the catalytic activity of the Cas9 enzyme to cleave DNA substrates containing nucleotide mismatch at different positions relative to the PAM in the “seed” sequence. We show that mismatches in the complementarity of the sgRNA/DNA duplex at different positions relative to the protospacer adjacent motif (PAM) sequence tend to decrease the cleavage efficiency and increase the half-maximal reaction time. However, for two mismatches at positions 11 and 20 relative to the PAM, an increase in cleavage efficiency was observed, both with and without an increase in half-reaction time. Thermodynamic parameters were obtained from molecular dynamics results, which showed that mismatches at positions 8, 11, and 20 relative to the PAM thermodynamically stabilize the formed complex, and a mismatch at position 2 of the PAM fragment exerts the greatest stabilization compared to the original DNA sequence. The weak correlation of the thermodynamic binding parameters of the components of the Cas9/sgRNA:dsDNA complex with the cleavage data of DNA substrates containing mismatches indicates that the efficiency of Cas9 operation is mainly affected by the conformational changes in Cas9 and the mutual arrangement of sgRNA and substrates. Full article

The demand for high-precision CRISPR/Cas9 systems in biomedicine is experiencing a notable upsurge. The editing system fdCas9 employs a dual-sgRNA strategy to enhance editing accuracy. However, the application of fdCas9 is constrained by the stringent requirement for two protospacer adjacent motifs (PAMs) of Cas9. Here, we devised an optimized editor, fRYdCas9, by merging FokI with the nearly PAM-less RYdCas9 variant, and two fRYdCas9 systems formed a dimer in a proper spacer length to accomplish DNA cleavage. In comparison to fdCas9, fRYdCas9 demonstrates a substantial increase in the number of editable genomic sites, approximately 330-fold, while maintaining a comparable level of editing efficiency. Through meticulous experimental validation, we determined that the optimal spacer length between two FokI guided by RYdCas9 is 16 base pairs. Moreover, fRYdCas9 exhibits a near PAM-less feature, along with no on-target motif preference via the library screening. Meanwhile, fRYdCas9 effectively addresses the potential risks of off-targets, as analyzed through whole genome sequencing (WGS). Mouse embryonic editing shows fRYdCas9 has robust editing capabilities. This study introduces a potentially beneficial alternative for accurate gene editing in therapeutic applications and fundamental research. Full article

Genome editing provides novel opportunities for the precise genome engineering of diverse organisms. Significant progress has been made in the development of genome-editing tools for Bombyx mori (B. mori) in recent years. Among these, CRISPR/Cas9, which is currently the most commonly used system in lepidopteran insects, recognizes NGG protospacer adjacent motif (PAM) sequences within the target locus. However, Cas9 lacks the ability to target all gene loci in B. mori, indicating the need for Cas9 variants with a larger editing range. In this study, we developed a high-throughput screening platform to validate Cas9 variants at all possible recognizable and editable PAM sites for target sequences in B. mori. This platform enabled us to identify PAM sites that can be recognized by both xCas9 3.7 and SpCas9-NG variants in B. mori and to assess their editing efficiency. Cas9 shows PAM sites every 13 base pairs in the genome, whereas xCas9 3.7 and SpCas9-NG have an average distance of 3.4 and 3.6 base pairs, respectively, between two specific targeting sites. Combining the two Cas9 variants could significantly expand the targeting range of the genome, accelerate research on the B. mori genome, and extend the high-throughput rapid screening platform to other insects, particularly those lacking suitable NGG PAM sequences. Full article

The CRISPR-Cas12a platform has attracted interest in the genome editing community because the prototypical Acidaminococcus Cas12a generates a staggered DNA double-strand break upon binding to an AT-rich protospacer-adjacent motif (PAM, 5′-TTTV). The broad application of the platform in primary human cells was enabled by the development of an engineered version of the natural Cas12a protein, called Cas12a Ultra. In this study, we confirmed that CRISPR-Cas12a Ultra ribonucleoprotein complexes enabled allelic gene disruption frequencies of over 90% at multiple target sites in human T cells, hematopoietic stem and progenitor cells (HSPCs), and induced pluripotent stem cells (iPSCs). In addition, we demonstrated, for the first time, the efficient knock-in potential of the platform in human iPSCs and achieved targeted integration of a GFP marker gene into the AAVS1 safe harbor site and a CSF2RA super-exon into CSF2RA in up to 90% of alleles without selection. Clonal analysis revealed bi-allelic integration in >50% of the screened iPSC clones without compromising their pluripotency and genomic integrity. Thus, in combination with the adeno-associated virus vector system, CRISPR-Cas12a Ultra provides a highly efficient genome editing platform for performing targeted knock-ins in human iPSCs. Full article

Acinetobacter baumannii is a low-GC-content Gram-negative opportunistic pathogen that poses a serious global public health threat. Convenient and rapid genetic manipulation is beneficial for elucidating its pathogenic mechanisms and developing novel therapeutic methods. In this study, we report a new CRISPR-FnCpf1-based two-plasmid system for versatile and precise genome editing in A. baumannii. After identification, this new system prefers to recognize the 5′-TTN-3′ (N = A, T, C or G) and the 5′-CTV-3′ (V = A, C or G) protospacer-adjacent motif (PAM) sequence and utilize the spacer with lengths ranging from 19 to 25 nt. In direct comparison with the existing CRISPR-Cas9 system, it exhibits approximately four times the targetable range in A. baumannii. Moreover, by employing a tandem dual crRNA expression cassette, the new system can perform large-fragment deletion and simultaneous multiple gene editing, which is difficult to achieve via CRISPR-Cas9. Therefore, the new system is valuable and can greatly expand the genome editing toolbox of A. baumannii. Full article

Prime editing is a rapidly developing method of CRISPR/Cas-based genome editing. The increasing number of novel PE applications and improved versions demands constant analysis and evaluation. The present review covers the mechanism of prime editing, the optimization of the method and the possible next step in the evolution of CRISPR/Cas9-associated genome editing. The basic components of a prime editing system are a prime editor fusion protein, consisting of nickase and reverse transcriptase, and prime editing guide RNA, consisting of a protospacer, scaffold, primer binding site and reverse transcription template. Some prime editing systems include other parts, such as additional RNA molecules. All of these components were optimized to achieve better efficiency for different target organisms and/or compactization for viral delivery. Insights into prime editing mechanisms allowed us to increase the efficiency by recruiting mismatch repair inhibitors. However, the next step in prime editing evolution requires the incorporation of new mechanisms. Prime editors combined with integrases allow us to combine the precision of prime editing with the target insertion of large, several-kilobase-long DNA fragments. Full article

Clustered regularly interspaced short palindromic repeats (CRISPR)- CRISPR-associated protein 9 (Cas9) genome editing technology is widely used for gene editing because it provides versatility in genetic manipulation. Several methods for regulating CRISPR activity already exist for accurate editing, but these require complex engineering. Thus, a simple and convenient regulatory system is required. In this study, we devised a CRISPR activation system using a DNA regulator that can be activated by miRNAs. The designed regulator was divided into two parts. The inhibition component consisted of the protospacer-adjacent motif (PAM) and seed sequence, which are important for Cas9 target recognition and bind to the ribonucleoprotein (RNP) complex for inhibition. The miRNA recognition component has a single-stranded toehold DNA for target miRNA binding and a partial double-stranded DNA complementary to the remaining miRNA sequence. In the presence of target miRNAs, the structure of the regulator is disrupted by the miRNAs, leading to its dissociation from the RNP complex and subsequent restoration of CRISPR activity. This method is easy to design and can be applied to various miRNAs via simple sequence manipulation. Therefore, this strategy provides a general platform for controlled genome editing. Full article

The advancement in CRISPR-Cas biosensors has transmuted the detection of plant viruses owing to their rapid and higher sensitivity. However, false positives and restricted multiplexing capabilities are still the challenges faced by this technology, demanding the exploration of novel methodologies. In this study, a novel detection system was developed by integrating reverse transcriptome (RT) techniques with recombinase polymerase isothermal amplification (RPA) and Pyrococcus furiosus Argonaute (PfAgo). The RT-RPA-PfAgo system enabled the simultaneous detection of rice ragged stunt virus (RRSV), rice grassy stunt virus (RGSV), and rice black streaked dwarf virus (RBSDV). Identifying targets via guide DNA without being hindered by protospacer adjacent motif sequences is the inherent merit of PfAgo, with the additional advantage of it being simple, cost-effective, and exceptionally sensitive, with detection limits between 3.13 and 5.13 copies/µL, in addition to it effectively differentiating between the three distinct viruses. The field evaluations were also in accordance with RT-PCR methods. The RT-RPA-PfAgo system proved to be a robust, versatile, highly specific, and sensitive method with great potential for practicality in future plant virus diagnostics. Full article

The innovative advances in transforming clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) into different variants have taken the art of genome-editing specificity to new heights. Allosteric modulation of Cas9-targeting specificity by sgRNA sequence alterations and protospacer adjacent motif (PAM) modifications have been a good lesson to learn about specificity and activity scores in different Cas9 variants. Some of the high-fidelity Cas9 variants have been ranked as Sniper-Cas9, eSpCas9 (1.1), SpCas9-HF1, HypaCas9, xCas9, and evoCas9. However, the selection of an ideal Cas9 variant for a given target sequence remains a challenging task. A safe and efficient delivery system for the CRISPR/Cas9 complex at tumor target sites faces considerable challenges, and nanotechnology-based stimuli-responsive delivery approaches have significantly contributed to cancer management. Recent innovations in nanoformulation design, such as pH, glutathione (GSH), photo, thermal, and magnetic responsive systems, have modernized the art of CRISPR/Cas9 delivery approaches. These nanoformulations possess enhanced cellular internalization, endosomal membrane disruption/bypass, and controlled release. In this review, we aim to elaborate on different CRISPR/Cas9 variants and advances in stimuli-responsive nanoformulations for the specific delivery of this endonuclease system. Furthermore, the critical constraints of this endonuclease system on clinical translations towards the management of cancer and prospects are described. Full article