Highly efficient and specific regulation of gene expression using enhanced CRISPR-Cas12f system.

The recently developed CRISPR activator (CRISPRa) system uses a CRISPR-Cas effector-based transcriptional activator to effectively control the expression of target genes without causing DNA damage. However, existing CRISPRa systems based on Cas9/Cas12a necessitate improvement in terms of efficacy and accuracy due to limitations associated with the CRISPR-Cas module itself. To overcome these limitations and effectively and accurately regulate gene expression, we developed an efficient CRISPRa system based on the small CRISPR-Cas effector Candidatus Woesearchaeota Cas12f (CWCas12f). By engineering the CRISPR-Cas module, linking activation domains, and using various combinations of linkers and nuclear localization signal sequences, the optimized eCWCas12f-VPR system enabled effective and target-specific regulation of gene expression compared with that using the existing CRISPRa system. The eCWCas12f-VPR system developed in this study has substantial potential for controlling the transcription of endogenous genes in living organisms and serves as a foundation for future gene therapy and biological research.

Splicing-independent loading of TREX on nascent RNA is required for efficient expression of dual-strand piRNA clusters in Drosophila.

The conserved THO/TREX (transcription/export) complex is critical for pre-mRNA processing and mRNA nuclear export. In metazoa, TREX is loaded on nascent RNA transcribed by RNA polymerase II in a splicing-dependent fashion; however, how TREX functions is poorly understood. Here we show that Thoc5 and other TREX components are essential for the biogenesis of piRNA, a distinct class of small noncoding RNAs that control expression of transposable elements (TEs) in the Drosophila germline. Mutations in TREX lead to defects in piRNA biogenesis, resulting in derepression of multiple TE families, gametogenesis defects, and sterility. TREX components are enriched on piRNA precursors transcribed from dual-strand piRNA clusters and colocalize in distinct nuclear foci that overlap with sites of piRNA transcription. The localization of TREX in nuclear foci and its loading on piRNA precursor transcripts depend on Cutoff, a protein associated with chromatin of piRNA clusters. Finally, we show that TREX is required for accumulation of nascent piRNA precursors. Our study reveals a novel splicing-independent mechanism for TREX loading on nascent RNA and its importance in piRNA biogenesis.

Aub and Ago3 Are Recruited to Nuage through Two Mechanisms to Form a Ping-Pong Complex Assembled by Krimper.

In Drosophila, two Piwi proteins, Aubergine (Aub) and Argonaute-3 (Ago3), localize to perinuclear "nuage" granules and use guide piRNAs to target and destroy transposable element transcripts. We find that Aub and Ago3 are recruited to nuage by two different mechanisms. Aub requires a piRNA guide for nuage recruitment, indicating that its localization depends on recognition of RNA targets. Ago3 is recruited to nuage independently of a piRNA cargo and relies on interaction with Krimper, a stable component of nuage that is able to aggregate in the absence of other nuage proteins. We show that Krimper interacts directly with Aub and Ago3 to coordinate the assembly of the ping-pong piRNA processing (4P) complex. Symmetrical dimethylated arginines are required for Aub to interact with Krimper, but they are dispensable for Ago3 to bind Krimper. Our study reveals a multi-step process responsible for the assembly and function of nuage complexes in piRNA-guided transposon repression.

Subcellular progression of mesenchymal transition identified by two discrete synchronous cell lines derived from the same glioblastoma.

Glioblastomas (GBM) exhibit intratumoral heterogeneity of various oncogenic evolutional processes. We have successfully isolated and established two distinct cancer cell lines with different morphological and biological characteristics that were derived from the same tissue sample of a GBM. When we compared their genomic and transcriptomic characteristics, each cell line harbored distinct mutation clusters while sharing core driver mutations. Transcriptomic analysis revealed that one cell line was undergoing a mesenchymal transition process, unlike the other cell line. Furthermore, we could identify four tumor samples containing our cell line-like clusters from the publicly available single-cell RNA-seq data, and in a set of paired longitudinal GBM samples, we could confirm three pairs where the recurrent sample was enriched in the genes specific to our cell line undergoing mesenchymal transition. The present study provides direct evidence and a valuable source for investigating the ongoing process of subcellular mesenchymal transition in GBM, which has prognostic and therapeutic implications.

Enhancement of target specificity of CRISPR-Cas12a by using a chimeric DNA-RNA guide.

The CRISPR-Cas9 system is widely used for target-specific genome engineering. CRISPR-Cas12a (Cpf1) is one of the CRISPR effectors that controls target genes by recognizing thymine-rich protospacer adjacent motif (PAM) sequences. Cas12a has a higher sensitivity to mismatches in the guide RNA than does Cas9; therefore, off-target sequence recognition and cleavage are lower. However, it tolerates mismatches in regions distant from the PAM sequence (TTTN or TTN) in the protospacer, and off-target cleavage issues may become more problematic when Cas12a activity is improved for therapeutic purposes. Therefore, we investigated off-target cleavage by Cas12a and modified the Cas12a (cr)RNA to address the off-target cleavage issue. We developed a CRISPR-Cas12a that can induce mutations in target DNA sequences in a highly specific and effective manner by partially substituting the (cr)RNA with DNA to change the energy potential of base pairing to the target DNA. A model to explain how chimeric (cr)RNA guided CRISPR-Cas12a and SpCas9 nickase effectively work in the intracellular genome is suggested. Chimeric guide-based CRISPR- Cas12a genome editing with reduced off-target cleavage, and the resultant, increased safety has potential for therapeutic applications in incurable diseases caused by genetic mutations.

Piwi induces piRNA-guided transcriptional silencing and establishment of a repressive chromatin state.

In the metazoan germline, piwi proteins and associated piwi-interacting RNAs (piRNAs) provide a defense system against the expression of transposable elements. In the cytoplasm, piRNA sequences guide piwi complexes to destroy complementary transposon transcripts by endonucleolytic cleavage. However, some piwi family members are nuclear, raising the possibility of alternative pathways for piRNA-mediated regulation of gene expression. We found that Drosophila Piwi is recruited to chromatin, colocalizing with RNA polymerase II (Pol II) on polytene chromosomes. Knockdown of Piwi in the germline increases expression of transposable elements that are targeted by piRNAs, whereas protein-coding genes remain largely unaffected. Derepression of transposons upon Piwi depletion correlates with increased occupancy of Pol II on their promoters. Expression of piRNAs that target a reporter construct results in a decrease in Pol II occupancy and an increase in repressive H3K9me3 marks and heterochromatin protein 1 (HP1) on the reporter locus. Our results indicate that Piwi identifies targets complementary to the associated piRNA and induces transcriptional repression by establishing a repressive chromatin state when correct targets are found.

Lipopeptide-Based Nanosome-Mediated Delivery of Hyperaccurate CRISPR/Cas9 Ribonucleoprotein for Gene Editing.

A transient cytosolic delivery system for accurate Cas9 ribonucleoprotein is a key factor for target specificity of the CRIPSR/Cas9 toolkit. Owing to the large size of the Cas9 protein and a long negative strand RNA, the development of the delivery system is still a major challenge. Here, a size-controlled lipopeptide-based nanosome system is reported, derived from the blood-brain barrier-permeable dNP2 peptide which is capable of delivering a hyperaccurate Cas9 ribonucleoprotein complex (HypaRNP) into human cells for gene editing. Each nanosome is capable of encapsulating and delivering ≈2 HypaRNP molecules into the cytoplasm, followed by nuclear localization at 4 h post-treatment without significant cytotoxicity. The HypaRNP thus efficiently enacts endogenous eGFP silencing and editing in human embryonic kidney cells (up to 27.6%) and glioblastoma (up to 19.7% frequency of modification). The lipopeptide-based nanosome system shows superior delivery efficiency, high controllability, and simplicity, thus providing biocompatibility and versatile platform approach for CRISPR-mediated transient gene editing applications.

Advances in diagnostic methods for keloids and biomarker-targeted fluorescent probes.

A keloid is a type of unusually raised scar. Unlike other raised scars, keloids form larger sizes than the wound site due to overgrowth, generally related to various biological factors. To date, only a few diagnostic and therapeutic methods for keloids have been reported. The high recurrence rates and undesirable side effects of keloids, at the end stage, encourage the invention of novel diagnostic tools, in order to cure keloids at an earlier stage. In this review, we summarize the general information about keloid diagnosis, keloid biomarkers, and recently reported fluorescent probes that can sense the key biomarkers of keloids. The focused description of fluorescent probes for keloid biomarkers and the author's perspective give useful insights in order to design the next-generation diagnostic sensing system for keloids.

Specificity Assessment of CRISPR Genome Editing of Oncogenic EGFR Point Mutation with Single-Base Differences.

In CRISPR genome editing, CRISPR proteins form ribonucleoprotein complexes with guide RNAs to bind and cleave the target DNAs with complete sequence complementarity. CRISPR genome editing has a high potential for use in precision gene therapy for various diseases, including cancer and genetic disorders, which are caused by DNA mutations within the genome. However, several studies have shown that targeting the DNA via sequence complementarity is imperfect and subject to unintended genome editing of other genomic loci with similar sequences. These off-target problems pose critical safety issues in the therapeutic applications of CRISPR technology, with particular concerns in terms of the genome editing of pathogenic point mutations, where non-mutant alleles can become an off-target with only a one-base difference. In this study, we sought to assess a novel CRISPR genome editing technique that has been proposed to achieve a high specificity by positioning the mismatches within the protospacer adjacent motif (PAM) sequence. To this end, we compared the genome editing specificities of the PAM-based and conventional methods on an oncogenic single-base mutation in the endothelial growth factor receptor (EGFR). The results indicated that the PAM-based method provided a significantly increased genome editing specificity for pathogenic mutant alleles with single-base precision.

Prokaryotic Argonautes defend genomes against invasive DNA.

Argonaute proteins are central players in small RNA-mediated silencing mechanisms such as RNA interference (RNAi), microRNA repression and piRNA-mediated transposon silencing. In eukaryotes, Argonautes bind small RNAs that guide them to RNA targets in order to regulate gene expression and repress invasive genomic elements. Although Argonaute proteins are conserved in all life forms from bacteria to eukaryotes, until now studies have focused on the biological functions of eukaryotic Argonautes. Here we highlight two recent studies that discover the functions of prokaryotic Argonautes in defence against exogenous DNA.

Myofibroblast in the ligamentum flavum hypertrophic activity.

PURPOSE: Majority of the previous studies compared lumbar spinal stenosis (LSS) and lumbar disc herniation (LDH) patients for analyses of LFH. However, the separation of normal/hypertrophied LF has often been ambiguous and the severity of hypertrophic activity differed. Here, we present a novel analysis scheme for LFH in which myofibroblast is proposed as a major etiological factor for LFH study. METHODS: Seventy-one LF patient tissue samples were used for this study. Initially, mRNA levels of the samples were assessed by qRT-PCR: angiopoietin-like protein-2 (ANGPTL2), transforming growth factor-beta1 (TGF-ß1), vascular endothelial growth factor (VEGF), interleukin-6, collagen-1, 3, 4, 5, and 11, and elastin. Myofibroblasts were detected by immune stain using α-smooth muscle actin (αSMA) as a marker. To study the myofibroblast in TGF-ß pathway, LF tissues were analyzed for protein levels of αSMA/TGF-ß1 by Western blot. In addition, from LF cells cultured with exogenous TGF-ß1 conditioned medium, expression of αSMA/collagen-1 was assessed and the cell morphology was identified. RESULTS: The comparative analysis of mRNA expression levels (LSS vs LDH) failed to show significant differences in TGF-ß1 (p = 0.08); however, we found a significant positive correlation among ANGPTL2, VEGF, TGF-ß1, and collagen-1 and 3, which represent common trends in hypertrophic activity (p < 0.05). We detected myofibroblast in the patient samples by αSMA staining, and the protein levels of αSMA were positively correlated with TGF-ß1. In LF cell culture, exogenous TGF-ß1 upregulated αSMA/collagen-1 mRNA levels and facilitated trans-differentiation to myofibroblast. CONCLUSIONS: We conclude that the transition of fibroblast to myofibroblasts via TGF-ß pathway is a key linker between inflammation and fibrosis in LFH mechanism.

Regulation of Argonaute slicer activity by guide RNA 3' end interactions with the N-terminal lobe.

Structural studies indicate that binding of both the guide RNA (siRNA and miRNA) and the target mRNA trigger substantial conformational changes in the Argonaute proteins. Here we explore the role of the N-terminal lobe (and its PAZ domain) in these conformational changes using biochemical and cell culture-based approaches. In vitro, whereas deletion (or mutation) of the N-terminal lobe of DmAgo1 and DmAgo2 had no effect on binding affinity to guide RNAs, we observed a loss of protection of the 3' end of the guide RNA and decreased target RNA binding; consistent with this, in cells, loss of function DmAgo1 PAZ variant proteins (PAZ6 and ΔN-PAZ) still bind RNA, although the RNAs are shorter than normal. We also find that deletion of the N-terminal lobe results in constitutive activation of endogenous PIWI domain-based cleavage activity in vitro, providing insights into how cleavage activity may be regulated in vivo in response to different types of pairing interactions with the target mRNAs.

Applications of CRISPR technologies to the development of gene and cell therapy.

Advancements in gene and cell therapy have resulted in novel therapeutics for diseases previously considered incurable or challenging to treat. Among the various contributing technologies, genome editing stands out as one of the most crucial for the progress in gene and cell therapy. The discovery of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) and the subsequent evolution of genetic engineering technology have markedly expanded the field of target-specific gene editing. Originally studied in the immune systems of bacteria and archaea, the CRISPR system has demonstrated wide applicability to effective genome editing of various biological systems including human cells. The development of CRISPR-based base editing has enabled directional cytosine-tothymine and adenine-to-guanine substitutions of select DNA bases at the target locus. Subsequent advances in prime editing further elevated the flexibility of the edit multiple consecutive bases to desired sequences. The recent CRISPR technologies also have been actively utilized for the development of in vivo and ex vivo gene and cell therapies. We anticipate that the medical applications of CRISPR will rapidly progress to provide unprecedented possibilities to develop novel therapeutics towards various diseases. [BMB Reports 2024; 57(1): 2-11].

CORRIGENDUM: Correction of the ACKNOWLEDGEMENTS (Fund/Grant Support). Epigenetic modulation inhibits epithelial-mesenchymal transition-driven fibrogenesis and enhances characteristics of chemically-derived hepatic progenitors.

[This corrects the article on p. 274 in vol. 106, PMID: 38725803.].

Epigenetic modulation inhibits epithelial-mesenchymal transition-driven fibrogenesis and enhances characteristics of chemically-derived hepatic progenitors.

Purpose: One of the novel cell sources of cell-based liver regenerative medicine is human chemically-derived hepatic progenitors (hCdHs). We previously established this cell by direct hepatocyte reprogramming with a combination of small molecules (hepatocyte growth factor, A83-01, CHIR99021). However, there have been several issues concerning the cell's stability and maintenance, namely the occurrences of epithelial-mesenchymal transition (EMT) that develop fibrotic phenotypes, resulting in the loss of hepatic progenitor characteristics. These hepatic progenitor attributes are thought to be regulated by SOX9, a transcription factor essential for hepatic progenitor cells and cholangiocytes. Methods: To suppress the fibrotic phenotype and improve our long-term hCdHs culture technology, we utilized the epigenetic modulating drugs DNA methyltransferase inhibitor (5-azacytidine) and histone deacetylase inhibitor (sodium butyrate) that have been reported to suppress and revert hepatic fibrosis. To confirm the essential role of SOX9 to our cell, we used clustered regularly interspaced short palindromic repeats-interference (CRISPRi) to repress the SOX9 expression. Results: The treatment of only 5-azacytidine significantly reduces the fibrosis/mesenchymal marker and EMT-related transcription factor expression level in the early passages. Interestingly, this treatment also increased the hepatic progenitor markers expression, even during the reprogramming phase. Then, we confirmed the essential role of SOX9 by repressing the SOX9 expression with CRISPRi which resulted in the downregulation of several essential hepatic progenitor cell markers. Conclusion: These results highlight the capacity of 5-azacytidine to inhibit EMT-driven hepatic fibrosis and the significance of SOX9 on hepatic progenitor cell stemness properties.

Utilization of nicking properties of CRISPR-Cas12a effector for genome editing.

The CRISPR-Cas nickase system for genome editing has attracted considerable attention owing to its safety, efficiency, and versatility. Although alternative effectors to Cas9 have the potential to expand the scope of genome editing, their application has not been optimized. Herein, we used an enhanced CRISPR-Cas12a nickase system to induce mutations by targeting genes in a human-derived cell line. The optimized CRISPR-Cas12a nickase system effectively introduced mutations into target genes under a specific directionality and distance between nickases. In particular, the single-mode Cas12a nickase system can induce the target-specific mutations with less DNA double-strand breaks. By inducing mutations in the Thymine-rich target genes in single- or dual-mode, Cas12a nickase compensates the limitations of Cas9 nickase and is expected to contribute to the development of future genome editing technologies.

Epigenetic modification of gene expression in cancer cells by terahertz demethylation.

Terahertz (THz) radiation can affect the degree of DNA methylation, the spectral characteristics of which exist in the terahertz region. DNA methylation is an epigenetic modification in which a methyl (CH3) group is attached to cytosine, a nucleobase in human DNA. Appropriately controlled DNA methylation leads to proper regulation of gene expression. However, abnormal gene expression that departs from controlled genetic transcription through aberrant DNA methylation may occur in cancer or other diseases. In this study, we demonstrate the modification of gene expression in cells by THz demethylation using resonant THz radiation. Using an enzyme-linked immunosorbent assay, we observed changes in the degree of global DNA methylation in the SK-MEL-3 melanoma cell line under irradiation with 1.6-THz radiation with limited spectral bandwidth. Resonant THz radiation demethylated living melanoma cells by 19%, with no significant occurrence of apurinic/apyrimidinic sites, and the demethylation ratio was linearly proportional to the power of THz radiation. THz demethylation downregulates FOS, JUN, and CXCL8 genes, which are involved in cancer and apoptosis pathways. Our results show that THz demethylation has the potential to be a gene expression modifier with promising applications in cancer treatment.

CRISPR-clear imaging of melanin-rich B16-derived solid tumors.

Tissue clearing combined with deep imaging has emerged as a powerful technology to expand classical histological techniques. Current techniques have been optimized for imaging sparsely pigmented organs such as the mammalian brain. In contrast, melanin-rich pigmented tissue, of great interest in the investigation of melanomas, remains challenging. To address this challenge, we have developed a CRISPR-based gene editing approach that is easily incorporated into existing tissue-clearing workflows such the PACT clearing method. We term this method CRISPR-Clear. We demonstrate its applicability to highly melanin-rich B16-derived solid tumors, including one made transgenic for HER2, constituting one of very few syngeneic mouse tumors that can be used in immunocompetent models. We demonstrate the utility in detailed tumor characterization by staining for targeting antibodies and nanoparticles, as well as expressed fluorescent proteins. With CRISPR-Clear we have unprecedented access to optical interrogation in considerable portions of intact melanoma tissue for stained surface markers, expressed fluorescent proteins, of subcellular compartments, and of the vasculature.

Spatial Transcriptomics: Technical Aspects of Recent Developments and Their Applications in Neuroscience and Cancer Research.

Spatial transcriptomics is a newly emerging field that enables high-throughput investigation of the spatial localization of transcripts and related analyses in various applications for biological systems. By transitioning from conventional biological studies to "in situ" biology, spatial transcriptomics can provide transcriptome-scale spatial information. Currently, the ability to simultaneously characterize gene expression profiles of cells and relevant cellular environment is a paradigm shift for biological studies. In this review, recent progress in spatial transcriptomics and its applications in neuroscience and cancer studies are highlighted. Technical aspects of existing technologies and future directions of new developments (as of March 2023), computational analysis of spatial transcriptome data, application notes in neuroscience and cancer studies, and discussions regarding future directions of spatial multi-omics and their expanding roles in biomedical applications are emphasized.

Extru-seq: a method for predicting genome-wide Cas9 off-target sites with advantages of both cell-based and in vitro approaches.

We present a novel genome-wide off-target prediction method named Extru-seq and compare it with cell-based (GUIDE-seq), in vitro (Digenome-seq), and in silico methods using promiscuous guide RNAs with large numbers of valid off-target sites. Extru-seq demonstrates a high validation rate and retention of information about the intracellular environment, both beneficial characteristics of cell-based methods. Extru-seq also shows a low miss rate and could easily be performed in clinically relevant cell types with little optimization, which are major positive features of the in vitro methods. In summary, Extru-seq shows beneficial features of cell-based and in vitro methods.