TRIM14 Inhibits cGAS Degradation Mediated by Selective Autophagy Receptor p62 to Promote Innate Immune Responses.

Cyclic GMP-AMP synthase (cGAS) is an essential DNA virus sensor that triggers type I interferon (IFN) signaling by producing cGAMP to initiate antiviral immunity. However, post-translational regulation of cGAS remains largely unknown. We report that K48-linked ubiquitination of cGAS is a recognition signal for p62-depdendent selective autophagic degradation. The induction of TRIM14 by type I IFN accelerates cGAS stabilization by recruiting USP14 to cleave the ubiquitin chains of cGAS at lysine (K) 414. Knockout of TRIM14 impairs herpes simplex virus type 1 (HSV-1)-triggered antiviral responses in a cGAS-dependent manner. Due to impaired type I IFN production, Trim14-/- mice are highly susceptible to lethal HSV-1 infection. Taken together, our findings reveal a positive feedback loop of cGAS signaling generated by TRIM14-USP14 and provide insights into the crosstalk between autophagy and type I IFN signaling in innate immunity.

Dual-AAV delivering split prime editor system for in vivo genome editing.

Prime editor (PE), a new genome editing tool, can generate all 12 possible base-to-base conversions, insertion, and deletion of short fragment DNA. PE has the potential to correct the majority of known human genetic disease-related mutations. Adeno-associated viruses (AAVs), the safe vector widely used in clinics, are not capable of delivering PE (∼6.3 kb) in a single vector because of the limited loading capacity (∼4.8 kb). To accommodate the loading capacity of AAVs, we constructed four split-PE (split-PE994, split-PE1005, split-PE1024, and split-PE1032) using Rma intein (Rhodothermus marinus). With the use of a GFP-mutated reporter system, PE reconstituting activities were screened, and two efficient split-PEs (split-PE1005 and split-PE1024) were identified. We then demonstrated that split-PEs delivered by dual-AAV1, especially split-PE1024, could mediate base transversion and insertion at four endogenous sites in human cells. To test the performance of split-PE in vivo, split-PE1024 was then delivered into the adult mouse retina by dual-AAV8. We demonstrated successful editing of Dnmt1 in adult mouse retina. Our study provides a new method to deliver PE to adult tissue, paving the way for in vivo gene-editing therapy using PE.

Single AAV-mediated CRISPR-Nme2Cas9 efficiently reduces mutant hTTR expression in a transgenic mouse model of transthyretin amyloidosis.

Transthyretin (TTR) amyloidosis is a hereditary life-threatening disease characterized by deposition of amyloid fibrils. The main causes of TTR amyloidosis are mutations in the TTR gene that lead to the production of misfolded TTR protein. Reducing the production of toxic protein in the liver is a validated strategy to treat TTR amyloidosis. In this study, we established a humanized mouse model that expresses mutant human TTR (hTTR; V30M) protein in the liver to model TTR amyloidosis. Then, we compared the efficiency of reducing the expression of mutant hTTR by dual adeno-associated virus 8 (AAV8)-mediated split SpCas9 with that by single AAV8-mediated Nme2Cas9 in this model. With two gRNAs targeting different exons, dual AAV-mediated split SpCas9 system achieved efficiencies of 37% and 34% reduction of hTTR mRNA and reporter GFP expression, respectively, in the liver. Surprisingly, single AAV-mediated Nme2Cas9 treatment resulted in 65% and 71% reduction of hTTR mRNA and reporter GFP, respectively. No significant editing was identified in predicted off-target sites in the mouse and human genomes after Nme2Cas9 targeting. Thus, we provide proof of principle for using single AAV-mediated CRISPR-Nme2Cas9 to effectively reduce mutant hTTR expression in vivo, which may translate into gene therapy for TTR amyloidosis.

Generation of C-to-G transversion in mouse embryos via CG editors.

Base editors (BEs) are efficient and precise tools for generating single base conversions in living organisms. While most BE systems are limited in mediating C-to-T or A-to-G conversions, recently developed C-to-G base editors (CGBEs) could produce C-to-G transversions. CGBEs convert cytosine within the editing window to abasic intermediates, which would be replaced with any base after base excision repair (BER). By far, though the efficiency and editing scope of CGBEs have been investigated in cultured cells via gRNA library and machine-learning, the viability of CGBEs in generating mouse models has not been adequately tested. In this study, we tested the C-to-G transversion efficiency of the CGBE1 and CGBE-XRCC1 systems in mouse embryos. Our results showed that both of the CGBE systems were able to mediate C-to-G transversion on 2 out of 3 targets tested, with up to 20% frequency within the editing window. Notably, most of the groups showed over 40% of other base conversions, predominantly C-to-T. Lastly, we successfully acquired the F1 mouse carrying a disease-causing mutation. In all, our study suggested that CGBEs systems held great potential in generating mouse models and indicated that XRCC1 based system is applicable in mouse embryos.

Benzo[a]pyrene promotes progression in tongue squamous cell carcinoma.

OBJECTIVES: Benzo[a]pyrene (B[a]P) is a member of the polycyclic aromatic hydrocarbon (PAH) family. Although the potent carcinogenicity of high-dose B[a]P has been extensively reported, the effects of long-term exposure to B[a]P on the progression of tongue squamous cell carcinoma (TSCC) are poorly understood. METHODS: In the present study, TSCC cells were treated with 5 or 50 nM of B[a]P for three months. The proliferation and chemoresistance of B[a]P-treated cells to 5-fluorouracil or cisplatin were detected by CCK8. The motility of the B[a]P-treated cells was evaluated with wound healing analysis, invasion assay, and three-dimensional culture in decellularized mouse tongue matrix. Xenograft assay was used to investigate the aggressiveness of B[a]P-treated cells. Immunofluorescence staining, terminal restriction fragment assay, and whole-genome sequence were used to determine the mutation spectrums. RESULTS: Long-term 50 nM B[a]P-treated cells exhibited increased aggressiveness and chemoresistance to 5-fluorouracil or cisplatin. In addition, data from whole-genome sequencing demonstrated that C:T to A:T transitions were the predominant nucleotide substitutions occurred in 50 nM B[a]P-treated CAL27 cells. Furthermore, 102 non-synonymous or stop-gain mutations were enriched in the extracellular-matrix-receptor interactive pathway. CONCLUSIONS: B[a]P exposure may contribute to genomic instability, and therefore, B[a]P may promote the progression of TSCC.

[Construction of a mouse model of cblC type methylmalonic acidemia with W203X mutation based on the CRISPR/Cas9 technology].

OBJECTIVE: To construct a W203X-mutant mouse model of cblC type methylmalonic acidemia based on the CRISPR/Cas9 technology. METHODS: At first, BLAST was used to compare the conservative nature of the cblC gene and protein sequences in humans and mice, and then, the CRISPR/Cas9 technology was used for microinjection of mouse fertilized eggs to obtain heterozygous F1 mice. Hybridization was performed for these mice to obtain homozygous W203X-mutant mice. The blood level of the metabolite propionyl carnitine (C3) was measured for homozygous mutant mice, heterozygous littermates, and wild-type mice. RESULTS: The gene and protein sequences of MMACHC, the pathogenic gene for cblC type methylmalonic acidemia, were highly conserved in humans and mice. The homozygous W203X-mutant mice were successfully obtained by the CRISPR/Cas9 technology, and there was a significant increase in C3 in these mice at 24 hours after birth (P<0.001). CONCLUSIONS: A W203X-mutant mouse model of cblC type methylmalonic acidemia is successfully constructed by the CRISPR/Cas9 technology.

Ccndbp1 is a new positive regulator of skeletal myogenesis.

Skeletal myogenesis is a multistep process in which basic helix-loop-helix (bHLH) transcription factors, such as MyoD (also known as MyoD1), bind to E-boxes and activate downstream genes. Ccndbp1 is a HLH protein that lacks a DNA-binding region, and its function in skeletal myogenesis is currently unknown. We generated Ccndbp1-null mice by using CRISPR-Cas9. Notably, in Ccndbp1-null mice, the cross sectional area of the skeletal tibialis anterior muscle was smaller, and muscle regeneration ability and grip strength were impaired, compared with those of wild type. This phenotype resembled that of myofiber hypotrophy in some human myopathies or amyoplasia. Ccndbp1 expression was upregulated during C2C12 myogenesis. Ccndbp1 overexpression promoted myogenesis, whereas knockdown of Ccndbp1 inhibited myogenic differentiation. Co-transfection of Ccndbp1 with MyoD and/or E47 (encoded by TCF3) significantly enhanced E-box-dependent transcription. Furthermore, Ccndbp1 physically associated with MyoD but not E47. These data suggest that Ccndbp1 regulates muscle differentiation by interacting with MyoD and enhancing its binding to target genes. Our study newly identifies Ccndbp1 as a positive modulator of skeletal myogenic differentiation in vivo and in vitro, providing new insights in order to decipher the complex network involved in skeletal myogenic development and related diseases.

pgRNAFinder: a web-based tool to design distance independent paired-gRNA.

SUMMARY: The CRISPR/Cas System has been shown to be an efficient and accurate genome-editing technique. There exist a number of tools to design the guide RNA sequences and predict potential off-target sites. However, most of the existing computational tools on gRNA design are restricted to small deletions. To address this issue, we present pgRNAFinder, with an easy-to-use web interface, which enables researchers to design single or distance-free paired-gRNA sequences. The web interface of pgRNAFinder contains both gRNA search and scoring system. After users input query sequences, it searches gRNA by 3' protospacer-adjacent motif (PAM), and possible off-targets, and scores the conservation of the deleted sequences rapidly. Filters can be applied to identify high-quality CRISPR sites. PgRNAFinder offers gRNA design functionality for 8 vertebrate genomes. Furthermore, to keep pgRNAFinder open, extensible to any organism, we provide the source package for local use. AVAILABILITY AND IMPLEMENTATION: The pgRNAFinder is freely available at http://songyanglab.sysu.edu.cn/wangwebs/pgRNAFinder/, and the source code and user manual can be obtained from https://github.com/xiexiaowei/pgRNAFinder. CONTACT: songyang@bcm.edu or daizhim@mail.sysu.edu.cn. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

CRISPR/Cas9 Technology Targeting Fas Gene Protects Mice From Concanavalin-A Induced Fulminant Hepatic Failure.

Fulminant hepatic failure is a life-threatening disease which occurs in patients without preexisting liver disease. Nowadays, there is no ideal therapeutic tool in the treatment of fulminant hepatic failure. Recent studies suggested that a novel technology termed CRISPR/Cas9 may be a promising approach for the treatment of fulminant hepatic failure. In this project, we have designed single chimeric guide RNAs specifically targeting the genomic regions of mouse Fas gene. The in vitro and in vivo effects of sgRNAs on the production of Fas protein were examined in cultured mouse cells and in a hydrodynamic injection-based mouse model, respectively. The in vivo delivery of CRISPR/Cas9 could maintain liver homeostasis and protect hepatocytes from Fas-mediated cell apoptosis in the fulminant hepatic failure model. Our study indicates the clinical potential of developing the CRISPR/Cas9 system as a novel therapeutic strategy to rescue Concanavalin-A-induced fulminant hepatic failure in the mouse model. J. Cell. Biochem. 118: 530-536, 2017. © 2016 Wiley Periodicals, Inc.

Developmental history and application of CRISPR in human disease.

Genome-editing tools are programmable artificial nucleases, mainly including zinc-finger nucleases, transcription activator-like effector nucleases and clustered regularly interspaced short palindromic repeat (CRISPR). By recognizing and cleaving specific DNA sequences, genome-editing tools make it possible to generate site-specific DNA double-strand breaks (DSBs) in the genome. DSBs will then be repaired by either error-prone nonhomologous end joining or high-fidelity homologous recombination mechanisms. Through these two different mechanisms, endogenous genes can be knocked out or precisely repaired/modified. Rapid developments in genome-editing tools, especially CRISPR, have revolutionized human disease models generation, for example, various zebrafish, mouse, rat, pig, monkey and human cell lines have been constructed. Here, we review the developmental history of CRISPR and its application in studies of human diseases. In addition, we also briefly discussed the therapeutic application of CRISPR in the near future.

MiR-25 suppresses 3T3-L1 adipogenesis by directly targeting KLF4 and C/EBPα.

In the past decade, miRNA emerges as a vital player in orchestrating gene regulation and maintaining cellular homeostasis. It is well documented that miRNA influences a variety of biological events, including embryogenesis, cell fate decision, and cellular differentiation. Adipogenesis is an organized process of cellular differentiation by which pre-adipocytes differentiate towards mature adipocytes. It has been shown that adipogenesis is tightly modulated by a number of transcription factors such as PPARγ, KLF4, and C/EBPα. However, the molecular mechanisms underlying the missing link between miRNA and adipogenesis-related transcription factors remain elusive. In this study, we unveiled that miR-25, a member of miR-106b-25 cluster, was remarkably downregulated during 3T3-L1 adipogenesis. Restored expression of miR-25 significantly impaired 3T3-L1 adipogenesis and downregulated the expression of serial adipogenesis-related genes. Further experiments presented that ectopic expression of miR-25 did not affect cell proliferation and cell cycle progression. Finally, KLF4 and C/EBPα, two key regulators of adipocyte differentiation, were experimentally identified as bona fide targets for miR-25. These data indicate that miR-25 is a novel negative regulator of adipocyte differentiation and it suppressed 3T3-L1 adipogenesis by targeting KLF4 and C/EBPα, which provides novel insights into the molecular mechanism of miRNA-mediated cellular differentiation.

Current therapies for osteoarthritis and prospects of CRISPR-based genome, epigenome, and RNA editing in osteoarthritis treatment.

Osteoarthritis (OA) is one of the most common degenerative joint diseases worldwide, causing pain, disability, and decreased quality of life. The balance between regeneration and inflammation-induced degradation results in multiple etiologies and complex pathogenesis of OA. Currently, there is a lack of effective therapeutic strategies for OA treatment. With the development of CRISPR-based genome, epigenome, and RNA editing tools, OA treatment has been improved by targeting genetic risk factors, activating chondrogenic elements, and modulating inflammatory regulators. Supported by cell therapy and in vivo delivery vectors, genome, epigenome, and RNA editing tools may provide a promising approach for personalized OA therapy. This review summarizes CRISPR-based genome, epigenome, and RNA editing tools that can be applied to the treatment of OA and provides insights into the development of CRISPR-based therapeutics for OA treatment. Moreover, in-depth evaluations of the efficacy and safety of these tools in human OA treatment are needed.

Correction of a CADASIL point mutation using adenine base editors in hiPSCs and blood vessel organoids.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a monogenic small vessel disease caused by mutations in the NOTCH3 gene. However, the pathogenesis of CADASIL remains unclear, and patients have limited treatment options. Here, we use human induced pluripotent stem cells (hiPSCs) generated from the peripheral blood mononuclear cells of a patient with CADASIL carrying a heterozygous NOTCH3 mutation (c.1261C>T, p.R421C) to develop a disease model. The correction efficiency of different adenine base editors (ABEs) is tested using the HEK293T-NOTCH3 reporter cell line. ABEmax is selected based on its higher efficiency and minimization of predicted off-target effects. Vascular smooth muscle cells (VSMCs) differentiated from CADASIL hiPSCs show NOTCH3 deposition and abnormal actin cytoskeleton structure, and the abnormalities are recovered in corrected hiPSC-derived VSMCs. Furthermore, CADASIL blood vessel organoids generated for in vivo modeling show altered expression of genes related to disease phenotypes, including the downregulation of cell adhesion, extracellular matrix organization, and vessel development. The dual adeno-associated virus (AAV) split-ABEmax system is applied to the genome editing of vascular organoids with an average editing efficiency of 8.82%. Collectively, we present potential genetic therapeutic strategies for patients with CADASIL using blood vessel organoids and the dual AAV split-ABEmax system.

CRISPR-assisted transcription activation by phase-separation proteins.

The clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system has been widely used for genome engineering and transcriptional regulation in many different organisms. Current CRISPR-activation (CRISPRa) platforms often require multiple components because of inefficient transcriptional activation. Here, we fused different phase-separation proteins to dCas9-VPR (dCas9-VP64-P65-RTA) and observed robust increases in transcriptional activation efficiency. Notably, human NUP98 (nucleoporin 98) and FUS (fused in sarcoma) IDR domains were best at enhancing dCas9-VPR activity, with dCas9-VPR-FUS IDR (VPRF) outperforming the other CRISPRa systems tested in this study in both activation efficiency and system simplicity. dCas9-VPRF overcomes the target strand bias and widens gRNA designing windows without affecting the off-target effect of dCas9-VPR. These findings demonstrate the feasibility of using phase-separation proteins to assist in the regulation of gene expression and support the broad appeal of the dCas9-VPRF system in basic and clinical applications.

Homology-based repair induced by CRISPR-Cas nucleases in mammalian embryo genome editing.

Recent advances in genome editing, especially CRISPR-Cas nucleases, have revolutionized both laboratory research and clinical therapeutics. CRISPR-Cas nucleases, together with the DNA damage repair pathway in cells, enable both genetic diversification by classical non-homologous end joining (c-NHEJ) and precise genome modification by homology-based repair (HBR). Genome editing in zygotes is a convenient way to edit the germline, paving the way for animal disease model generation, as well as human embryo genome editing therapy for some life-threatening and incurable diseases. HBR efficiency is highly dependent on the DNA donor that is utilized as a repair template. Here, we review recent progress in improving CRISPR-Cas nuclease-induced HBR in mammalian embryos by designing a suitable DNA donor. Moreover, we want to provide a guide for producing animal disease models and correcting genetic mutations through CRISPR-Cas nuclease-induced HBR in mammalian embryos. Finally, we discuss recent developments in precise genome-modification technology based on the CRISPR-Cas system.

Identification and Analysis of Small Molecule Inhibitors of CRISPR-Cas9 in Human Cells.

Genome editing tools based on CRISPR-Cas systems can repair genetic mutations in situ; however, off-target effects and DNA damage lesions that result from genome editing remain major roadblocks to its full clinical implementation. Protein and chemical inhibitors of CRISPR-Cas systems may reduce off-target effects and DNA damage. Here we describe the identification of several lead chemical inhibitors that could specifically inhibit the activity of Streptococcus pyogenes Cas9 (SpCas9). In addition, we obtained derivatives of lead inhibitors that could penetrate the cell membrane and inhibit SpCas9 in cellulo. Two of these compounds, SP2 and SP24, were able to improve the specificity of SpCas9 in cellulo at low-micromolar concentration. Furthermore, microscale thermophoresis (MST) assays showed that SP24 might inhibit SpCas9 activity by interacting with both the SpCas9 protein and the SpCas9-gRNA ribonucleoprotein complex. Taken together, SP24 is a novel chemical inhibitor of SpCas9 which has the potential to enhance therapies that utilize SpCas9.

USP19 suppresses inflammation and promotes M2-like macrophage polarization by manipulating NLRP3 function via autophagy.

Macrophage polarization to proinflammatory M1-like or anti-inflammatory M2-like cells is critical to mount a host defense or repair tissue. The exact molecular mechanisms controlling this process are still elusive. Here, we report that ubiquitin-specific protease 19 (USP19) acts as an anti-inflammatory switch that inhibits inflammatory responses and promotes M2-like macrophage polarization. USP19 inhibited NLRP3 inflammasome activation by increasing autophagy flux and decreasing the generation of mitochondrial reactive oxygen species. In addition, USP19 inhibited the proteasomal degradation of inflammasome-independent NLRP3 by cleaving its polyubiquitin chains. USP19-stabilized NLRP3 promoted M2-like macrophage polarization by direct association with interferon regulatory factor 4, thereby preventing its p62-mediated selective autophagic degradation. Consistent with these observations, compared to wild-type mice, Usp19-/- mice had decreased M2-like macrophage polarization and increased interleukin-1ß secretion, in response to alum and chitin injections. Thus, we have uncovered an unexpected mechanism by which USP19 switches the proinflammatory function of NLRP3 into an anti-inflammatory function, and suggest that USP19 is a potential therapeutic target for inflammatory interventions.

Effective generation of maternal genome point mutated porcine embryos by injection of cytosine base editor into germinal vesicle oocytes.

Cytosine and adenine base editors are promising new tools for introducing precise genetic modifications that are required to generate disease models and to improve traits in pigs. Base editors can catalyze the conversion of C→T (C>T) or A→G (A>G) in the target site through a single guide RNA. Injection of base editors into the zygote cytoplasm can result in the production of offspring with precise point mutations, but most F0 are mosaic, and breeding of F1 heterozygous pigs is time-intensive. Here, we developed a method called germinal vesicle oocyte base editing (GVBE) to produce point mutant F0 porcine embryos by editing the maternal alleles during the GV to MII transition. Injection of cytosine base editor 3 (BE3) mRNA and X-linked Dmd-specific guide RNAs into GVoocytes efficiently edited maternal Dmd during in vitro maturation and did not affect the maturation potential of the oocytes. The edited MII oocytes developed into blastocysts after parthenogenetic activation (PA) or in vitro fertilization (IVF). However, BE3 may reduce the developmental potential of IVF blastocysts from 31.5%±0.8% to 20.4% ±2.1%. There 40%-78.3% diploid PA blastocysts had no more than two different alleles, including up to 10% embryos that had only C>T mutation alleles. Genotyping of IVF blastocysts indicated that over 70% of the edited embryos had one allele or two different alleles of Dmd. Since the male embryos had only a copy of Dmd allele, all five (5/19) F0 male embryos are homozygous and three of them were Dmd precise C>T mutation. Nine (9/19) female IVF embryos had two different alleles including a WT and a C>T mutation. DNA sequencing showed that some of them might be heterozygous embryos. In conclusion, the GVBE method is a valuable method for generating F0 embryos with maternal point mutated alleles in a single step.