Kazuto Yoshimi

The CRISPR-Cas system is a powerful tool for generating genetically modified animals; however, targeted knock-in (KI) via homologous recombination remains difficult in zygotes. Here we show efficient gene KI in rats by combining CRISPR-Cas with single-stranded oligodeoxynucleotides (ssODNs). First, a 1-kb ssODN co-injected with guide RNA (gRNA) and Cas9 messenger RNA produce GFP-KI at the rat Thy1 locus. Then, two gRNAs with two 80-bp ssODNs direct efficient integration of a 5.5-kb CAG-GFP vecto

The bacterial CRISPR/Cas system has proven to be an efficient gene-targeting tool in various organisms. Here we employ CRISPR/Cas for accurate and efficient genome editing in rats. The synthetic chimeric guide RNAs (gRNAs) discriminate a single-nucleotide polymorphism (SNP) difference in rat embryonic fibroblasts, allowing allele-specific genome editing of the dominant phenotype in (F344 × DA)F1 hybrid embryos. Interestingly, the targeted allele, initially assessed by the allele-specific gRNA, i

CRISPR-based diagnostics (CRISPR-dx), including the Cas12-based DETECTR and Cas13-based SHERLOCK Class 2 CRISPRs, have been used to detect the presence of DNA or RNA from pathogens, such as the 2009 pandemic influenza virus A (IAV) and the 2019 novel coronavirus SARS-CoV-2. Here, we describe the collateral single-stranded DNA cleavage with Class 1 type I CRISPR-Cas3 and highlight its potential for development as a Cas3-mediated rapid (within 40 min), low-cost, instrument-free detection method fo

To establish an efficient rat model for colitis-associated colorectal cancer, azoxymethane and dextran sodium sulfate (AOM/DSS)-induced colon carcinogenesis was applied to a novel adenomatous polyposis coli (Apc) mutant, the Kyoto Apc Delta (KAD) rat. The KAD rat was derived from ethylnitrosourea mutagenesis and harbors a nonsense mutation in the Apc gene (S2523X). The truncated APC of the KAD rat was deduced to lack part of the basic domain, an EB1-binding domain, and a PDZ domain, but retained

CRISPR-Cas9 are widely used for gene targeting in mice and rats. The non-homologous end-joining (NHEJ) repair pathway, which is dominant in zygotes, efficiently induces insertion or deletion (indel) mutations as gene knockouts at targeted sites, whereas gene knock-ins (KIs) via homology-directed repair (HDR) are difficult to generate. In this study, we used a double-stranded DNA (dsDNA) donor template with Cas9 and two single guide RNAs, one designed to cut the targeted genome sequences and the

Type I CRISPR-Cas3 uses an RNA-guided multi Cas-protein complex, Cascade, which detects and degrades foreign nucleic acids via the helicase-nuclease Cas3 protein. Despite many studies using cryoEM and smFRET, the precise mechanism of Cas3-mediated cleavage and degradation of target DNA remains elusive. Here we reconstitute the CRISPR-Cas3 system in vitro to show how the Escherichia coli Cas3 (EcoCas3) with EcoCascade exhibits collateral non-specific single-stranded DNA (ssDNA) cleavage and targe

Novel coronavirus SARS-CoV-2 outbreaks have rapidly spread to multiple countries, highlighting the urgent necessity for fast, sensitive, and specific diagnostic tools for virus surveillance. Here, the previously unknown collateral single-stranded DNA cleavage we observed with type I CRISPR-Cas3 highlights its potential for development as a Cas3-mediated rapid (within 40 min), low-cost, instrument-free detection method for SARS-CoV-2. This Cas3-based assay is comparable with Cas12- and real-time

The use of the AOM/DSS-treated tumor-bearing KAD rats could shorten the experimental period and reduce the number of animals examined in the chemotherapeutic bioassay. The efficient bioassay with the AOM/DSS-treated tumor-bearing KAD rats would promote the development of new anti-tumor drugs and regimens.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems, which are representative genome editing technologies, are classified into class 1 and class 2 in terms of evolutionary biology and are further classified into several subtypes. Class 2 CRISPR systems, including type II Cas9 and type V Cas12a, are the most commonly used for genome editing in eukaryotic cells, while type I CRISPR systems within Class 1 are also becoming available. Type I CRISPR recognizes longer target

Repeat expansion disorders, exemplified by myotonic dystrophy type 1 (DM1), present challenges in diagnostic quantification because of the variability and complexity of repeat lengths. Traditional diagnostic methods, including PCR and Southern blotting, exhibit limitations in sensitivity and specificity, necessitating the development of innovative approaches for precise and rapid diagnosis. Here, we introduce a CRISPR-based diagnostic method, REPLICA (<u>re</u>peat-<u>p</u>rimed <u>l</u>ocating

The type I CRISPR system has recently emerged as a promising tool, especially for large-scale genomic modification, but its application to generate model animals by editing zygotes had not been established. In this study, we demonstrate genome editing in zygotes using the type I-E CRISPR-Cas3 system, which efficiently generates deletions of several thousand base pairs at targeted loci in mice with 40%-70% editing efficiency without off-target mutations. To overcome the difficulties associated wi