Rapid and sensitive point-of-care detection of Leptospira by RPA-CRISPR/Cas12a targeting lipL32

Background One of the key barriers preventing rapid diagnosis of leptospirosis is the lack of available sensitive point-of-care testing. This study aimed to develop and validate a clustered regularly-interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 12a (CRISPR/Cas12a) platform combined with isothermal amplification to detect leptospires from extracted patient DNA samples. Methodology/Principal findings A Recombinase Polymerase Amplification (RPA)-CRISPR/Cas12a-fluorescence assay was designed to detect the lipL32 gene of pathogenic Leptospira spp. The assays demonstrated a limit of detection (LOD) of 100 cells/mL, with no cross-reactivity against several other acute febrile illnesses. The clinical performance of the assay was validated with DNA extracted from 110 clinical specimens and then compared to results from qPCR detection of Leptospira spp. The RPA-CRISPR/Cas12a assay showed 85.2% sensitivity, 100% specificity, and 92.7% accuracy. The sensitivity increased on days 4–6 after the fever onset and decreased after day 7. The specificity was consistent for several days after the onset of fever. The overall performance of the RPA-CRISPR/Cas12a platform was better than the commercial rapid diagnostic test (RDT). We also developed a lateral flow detection assay (LFDA) combined with RPA-CRISPR/Cas12a to make the test more accessible and easier to interpret. The combined LFDA showed a similar LOD of 100 cells/mL and could correctly distinguish between known positive and negative clinical samples in a pilot study. Conclusions/Significance The RPA-CRISPR/Cas12 targeting the lipL32 gene demonstrated acceptable sensitivity and excellent specificity for detection of leptospires. This assay might be an appropriate test for acute leptospirosis screening in limited-resource settings.

CRISPR-Cas9-mediated mutagenesis of the SlSRM1-like gene leads to abnormal leaf development in tomatoes

Background Leaves, which are the most important organs of plants, can not only fix carbon sources through photosynthesis, but also absorb nutrients through transpiration. Leaf development directly determines the growth, flowering and fruiting of plants. There are many factors that affect leaf development, such as the growth environment, gene expression, and hormone synthesis. In this study, tomatoes were used to study the role of the transcription factor Solanum lycopersicum salt-related MYB1-like (SlSRM1-like) in the development of tomato leaves. Results Loss-of-function of the SlSRM1-like gene mediated by clustered, regularly interspaced, short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) resulted in abnormal tomato leaf morphology, including thinner leaves, wrinkled edges, raised veins, disordered edge veins, and left and right asymmetry. An analysis of the transcription levels of genes related to leaf development revealed that the expression of these genes was significantly altered in the SlSRM1-like mutants (SlSRM1-like-Ms). Moreover, the SlSRM1-like gene was expressed at higher transcription levels in young tissues than in old tissues, and its expression was also induced in response to auxin. In addition, the transcription levels of genes related to the auxin pathway, which regulates tomato growth and development, were severely affected in the SlSRM1-like-Ms. Therefore, it is hypothesized that the SlSRM1-like gene functions in the regulation of tomato leaf development through the auxin-related pathway. Conclusions In this study, we successfully knocked out the SlSRM1-like gene in the tomato variety Ailsa Craig using CRISPR technology and found that knockout of the SlSRM1-like gene resulted in abnormal development of tomato leaves. Further research indicated that SlSRM1-like regulated tomato leaf development through auxin-related pathways. The results provide an important reference for the functional study of other SRM1-like genes in plants and provide new insights into the regulation of leaf development in tomato and other plants.

Genome Editing and CRISPR/Cas System of Extremophiles and Its Applications

Extremophiles will be the choice of next generation industrial biotechnology (NGIB) as they are known to be contaminant resistant, but engineering their genomes has always been difficult and time consuming task. CRIPR/Cas (clustered regularly interspaced short palindromic repeat and CRISPR associated proteins) system can be employed for this reason. The genome of an industrially important halophile (i.e., Halomonas) was edited to study a combined effect of four different genes on glucose breakdown and production of poly (3-hydroxybutyrate-co-3-hydroxyvalerate). This editing has resulted in 16-fold increase of 3HV, and the mutants generated by CRIPR/Cas system were significantly effective in synthesizing PHBV. Unfortunately, this system does not always work, specifically in extremophilic microorganisms because Cas9 or Cpf1 are from mesophilic bacteria. Therefore, alternatively, the endogenous CRISPR/Cas system is used for editing the genomes of such organisms. This genome editing of extremophiles will open the doors for developing next generation industrial biotechnology (NGIB).

Insights into the Function of Regulatory RNAs in Bacteria and Archaea

Non-coding RNAs (ncRNAs) are functional RNA molecules that comprise about 80% of both mammals and prokaryotes genomes. Recent studies have identified a large number of small regulatory RNAs in Escherichia coli and other bacteria. In prokaryotes, RNA regulators are a diverse group of molecules that modulate a wide range of physiological responses through a variety of mechanisms. Similar to eukaryotes, bacterial microRNAs are an important class of ncRNAs that play an important role in the development and secretion of proteins and in the regulation of gene expression. Similarly, riboswitches are cis-regulatory structured RNA elements capable of directly controlling the expression of downstream genes in response to small molecule ligands. As a result, riboswitches detect and respond to the availability of various metabolic changes within cells. The most extensive and most widely studied set of small RNA regulators act through base pairing with RNAs. These types of RNAs are vital for prokaryotic life, activating or suppressing important physiological processes by modifying transcription or translation. The majority of these small RNAs control responses to changes in environmental conditions. Finally, clustered regularly interspaced short palindromic repeat (CRISPR) RNAs, a newly discovered RNA regulator group, contains short regions of homology to bacteriophage and plasmid sequences that bacteria use to splice phage DNA as a defense mechanism. The detailed mechanism is still unknown but devoted to target homologous foreign DNAs. Here, we review the known mechanisms and roles of non-coding regulatory RNAs, with particular attention to riboswitches and their functions, briefly introducing translational applications of CRISPR RNAs in mammals.

Whole gut virome analysis of 476 Japanese revealed a link between phage and autoimmune disease

ObjectiveThe relationship between autoimmune diseases and the gut microbiome has been intensively studied, and several autoimmunity-associated bacterial taxa have been identified. However, much less is known about the roles of the gut virome in autoimmune diseases.MethodsHere, we performed a whole gut virome analysis based on the shotgun sequencing of 476 Japanese which included patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis and healthy control subjects.ResultsOur case–control comparison of the viral abundance revealed that crAss-like phages, which are one of the main components of a healthy gut virome, significantly decreased in the gut of the patients with autoimmune disease, specifically the patients with RA and SLE. In addition, Podoviridae significantly decreased in the gut of the patients with SLE. To understand how these viruses affected the bacteriome, we performed a quantitative virus–bacterium association analysis and clustered regularly interspaced short palindromic repeat-based virus–bacterium interaction analysis. We identified a symbiosis between Podoviridae and Faecalibacterium. In addition, multiple bacterial targets of crAss-like phages were identified (eg, Ruminococcus spp).ConclusionOur data suggest that the gut virome can affect our body either directly or via bacteria. Our analyses have elucidated a previously missing part of the autoimmunity-associated gut microbiome and presented new candidates that contribute to the development of autoimmune diseases.

An Efficient Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR-Associated Protein 9 Mutagenesis System for Oil Palm (Elaeis guineensis)

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system has emerged as a powerful tool for the precise editing of plant genomes for crop improvement. Rapid in vitro methods for the determination of guide RNA (gRNA) cleavage efficiency and an efficient DNA delivery system is essential for gene editing. However, we lack an efficient gene-editing system for palm species. In this study, we described the development of a transient oil palm protoplast assay to rapidly evaluate the cleavage efficiency of CRISPR/Cas9 mutagenesis and the generation of stable transformed oil palms using biolistic particle bombardment in immature embryos. Using the phytoene desaturase (EgPDS) gene, we found cleavage frequency of up to 25.49% in electro-transfected protoplast, which enables the production of transgenic oil palm shoots exhibiting chimeric albino phenotypes as a result of DNA insertions, deletions (InDels), and nucleotide substitutions, with a mutation efficiency of 62.5–83.33%. We further validated the mutagenesis efficiency and specificity of the CRISPR/Cas9 system in oil palm by targeting the brassinosteroid-insensitive 1 (EgBRI1) gene, which resulted in nucleotide substitutions in EgBRI1 with premature necrosis phenotype in oil palm transgenic shoots and stunted phenotype resulting from DNA InDels. Taken together, our results showed that effective and efficient editing of genes using the CRISPR/Cas9 system can be achieved in oil palm by optimizing the selection of efficient gRNA and DNA delivery methods. This newly designed strategy will enable new routes for the genetic improvement in oil palm and related species.

Reversible regulation of Cas12a activities by AcrVA5-mediated acetylation and CobB-mediated deacetylation

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR associated (Cas) system protects bacteria and archaea from the invasion of foreign genetic elements. To cope with the host CRISPR systems, phages have evolved many strategies, including the anti-CRISPR (Acr) proteins, to inactivate the Cas nucleases. Recently, it has been reported that the type V-A Cas12a effector can be acetylated and inactivated by AcrVA5, which is a GNAT-family acetyltransferase. However, it is unclear whether the host has any coping strategies to reactivate the defense system. Here we show that the AcrVA5-acetylated Cas12a can be deacetylated by bacterial deacetylase CobB, reactivating Cas12a for both in vitro cleavage of target DNA sequences and in vivo protection of the host from invasion of foreign nucleic acids. Therefore, this study not only shows the reversible regulation of Cas12a activities by post-translational modification but also reveals CobB as a secondary safeguard to bacterial CRISPR defense systems. In addition, we demonstrate that AcrVA5 is a wide-spectrum acetyltransferase, acetylating a large number of target proteins besides Cas12a, and the AcrVA5-acetylated targets can also be deacetylated by CobB.

Study on Factors Affecting the Performance of a CRISPR/Cas-Assisted New Immunoassay: Detection of Salivary Insulin as an Example

The clustered regularly interspaced short palindromic repeat (CRISPR)/Cas is now playing a significant role in biosensing applications, especially when the trans-cleavage activity of several Cas effectors is discovered. Taking advantages of both CRISPR/Cas and the enzyme-linked immunosorbent assay (ELISA) in analytical and clinical investigations, CRISPR/Cas-powered ELISA has been successfully designed to detect a spectrum of analytes beyond nucleic acid. Herein, we developed a CRISPR/Cas12a-assisted new immunoassay (CANi) for detection of salivary insulin as an example. Specifically, factors (antibody selection, temperature, and assay time) affecting the CRISPR/Cas-based ELISA system’s performance were investigated. It was observed that the concentration of blocking solution, selection of the capture antibody pairs, and the sequences of triggering ssDNA and guiding RNA affected this immunoassay sensitivity. In contrast, the preincubation of CRISPR/Cas12a working solution and pre-mixture of detection antibody with anti-IgG–ssDNA did not show influence on the performance of CANi for the detection of insulin. Under optimized conditions, the sensitivity for detection of salivary insulin was 10 fg/ml with a linear range from 10 fg/ml to 1 ng/ml.

Targeted Inter-Homologs Recombination in Arabidopsis Euchromatin and Heterochromatin

Homologous recombination (HR) typically occurs during meiosis between homologs, at a few unplanned locations along the chromosomes. In this study, we tested whether targeted recombination between homologous chromosomes can be achieved via Clustered Regulatory Interspaced Short Palindromic Repeat associated protein Cas9 (CRISPR-Cas9)-induced DNA double-strand break (DSB) repair in Arabidopsis thaliana. Our experimental system includes targets for DSB induction in euchromatic and heterochromatic genomic regions of hybrid F1 plants, in one or both parental chromosomes, using phenotypic and molecular markers to measure Non-Homologous End Joining and HR repair. We present a series of evidence showing that targeted DSBs can be repaired via HR using a homologous chromosome as the template in various chromatin contexts including in pericentric regions. Targeted crossover was rare, but gene conversion events were the most frequent outcome of HR and were found in both “hot and cold” regions. The length of the conversion tracts was variable, ranging from 5 to 7505 bp. In addition, a typical feature of these tracks was that they often were interrupted. Our findings pave the way for the use of targeted gene-conversion for precise breeding.

Simple and Rapid Assembly of TALE Modules Based on the Degeneracy of the Codons and Trimer Repeats

Transcription activator-like effectors (TALEs) have been effectively used for targeted genome editing, transcriptional regulation, epigenetic modification, and locus-specific DNA imaging. However, with the advent of the clustered regularly interspaced short palindromic repeat/Cas9 system, an easy-to-use tool with the same function as TALEs, TALEs have recently been abandoned because of their complexity, time consumption, and difficult handling in common labs. Here, we described a degenerated codon-based TALE assembly system for simple, rapid, and efficient TALE assembly. TALE trimers with nonrepetitive DNA sequences were amplified by PCR and sequentially assembled via Gibson assembly. Our method is cost-effective, requires only commonly used basic molecular biology reagents, and takes only 2 h from target sequence analysis to completion. This simple, rapid, and lab-friendly TALE assembly method will restore the value of TALEs in DNA targeting.