Engineering IscB to develop highly efficient miniature editing tools in mammalian cells and embryos.

The IscB proteins, as the ancestors of Cas9 endonuclease, hold great promise due to their small size and potential for diverse genome editing. However, their activity in mammalian cells is unsatisfactory. By introducing three residual substitutions in IscB, we observed an average 7.5-fold increase in activity. Through fusing a sequence-non-specific DNA-binding protein domain, the eIscB-D variant achieved higher editing efficiency, with a maximum of 91.3%. Moreover, engineered ωRNA was generated with a 20% reduction in length and slightly increased efficiency. The engineered eIscB-D/eωRNA system showed an average 20.2-fold increase in activity compared with the original IscB. Furthermore, we successfully adapted eIscB-D for highly efficient cytosine and adenine base editing. Notably, eIscB-D is highly active in mouse cell lines and embryos, enabling the efficient generation of disease models through mRNA/ωRNA injection. Our study suggests that these miniature genome-editing tools have great potential for diverse applications.

Engineering of efficiency-enhanced Cas9 and base editors with improved gene therapy efficacies.

Editing efficiency is pivotal for the efficacies of CRISPR-based gene therapies. We found that fusing an HMG-D domain to the N terminus of SpCas9 (named efficiency-enhanced Cas9 [eeCas9]) significantly increased editing efficiency by 1.4-fold on average. The HMG-D domain also enhanced the activities of non-NGG PAM Cas9 variants, high-fidelity Cas9 variants, smaller Cas9 orthologs, Cas9-based epigenetic regulators, and base editors in cell lines. Furthermore, we discovered that eeCas9 exhibits comparable off-targeting effects with Cas9, and its specificity could be increased through ribonucleoprotein delivery or using hairpin single-guide RNAs and high-fidelity Cas9s. The entire eeCas9 could be packaged into an adeno-associated virus vector and exhibited a 1.7- to 2.6-fold increase in editing efficiency targeting the Pcsk9 gene in mice, leading to a greater reduction of serum cholesterol levels. Moreover, the efficiency of eeA3A-BE3 also surpasses that of A3A-BE3 in targeting the promoter region of γ-globin genes or BCL11A enhancer in human hematopoietic stem cells to reactivate γ-globin expression for the treatment of ß-hemoglobinopathy. Together, eeCas9 and its derivatives are promising editing tools that exhibit higher activity and therapeutic efficacy for both in vivo and ex vivo therapeutics.

Obesity induces male mice infertility via oxidative stress, apoptosis, and glycolysis.

In brief: The current declining trend in male fertility parallels the increasing prevalence of obesity worldwide. This paper revealed that the poor in vitro fertilization rates and decreased sperm motility in obese mice due to excessive oxidative stress enhanced apoptosis and impaired glucose metabolism in the testes. Abstract: Obesity is an urgent public health problem in recent decades, linked to reduced reproductive potential, and negatively affects the success of assisted reproduction technology. The aim of this study is to investigate the mechanisms underlying impaired male fertility caused by obesity. Male C57BL/6 mice fed a high-fat diet for 20 weeks served as mouse models with moderate (20% < body fat rate (BFR) < 30%) and severe obesity (BFR > 30%). Our results showed poor in vitro fertilization rates and decreased sperm motility in obese mice. Abnormal testicular structures were identified in male mice with moderate and severe obesity. The expression level of malondialdehyde increased with obesity severity. This finding indicates that oxidative stress plays a role in male infertility caused by obesity, which was further confirmed by the decreased expression of nuclear factor erythroid 2-related factor 2, superoxide dismutase, and glutathione peroxidases. Our study also found that the expression of cleaved caspase-3 and B-cell lymphoma-2 showed an obesity severity-dependent manner indicating that apoptosis is highly correlated with male infertility caused by obesity. Moreover, the expression of glycolysis-related proteins, including glucose transporter 8, lactate dehydrogenase A, monocarboxylate transporter 2 (MCT2), and MCT4, decreased significantly in the testes of obese male mice, suggesting energy supply for spermatogenesis is impaired by obesity. Taken together, our findings provide evidence that obesity impairs male fertility through oxidative stress, apoptosis, and blockage of energy supply in the testes and suggest that male obesity influences fertility through complex and multiple mechanisms.

Generation of genetically modified rat models via the CRISPR/Cas9 technology.

The RNA-guided CRISPR/Cas9 genomic editing system consists of a single guide RNA (sgRNA) and a Cas9 nuclease. The two components form a complex in cells and target the genomic loci complementary to the sgRNA. The Cas9 nuclease cleaves the target site creating a double stranded DNA break (DSB). In mammalian cells, DSBs are often repaired via error prone non-homologous end joining (NHEJ) or via homology directed repair (HDR) with the presence of donor DNA templates. Micro-injection of the CRISPR/Cas9 system into the rat embryos enables generation of genetically modified rat models. Here, we describe a detailed protocol for creating gene knockout or knockin rat models via the CRISPR/Cas9 technology.

Amelioration of an Inherited Metabolic Liver Disease through Creation of a De Novo Start Codon by Cytidine Base Editing.

Base editing technology efficiently generates nucleotide conversions without inducing excessive double-strand breaks (DSBs), which makes it a promising approach for genetic disease therapy. In this study, we generated a novel hereditary tyrosinemia type 1 (HT1) mouse model, which contains a start codon mutation in the fumarylacetoacetate hydrolase (Fah) gene by using an adenine base editor (ABE7.10). To investigate the feasibility of base editing for recombinant adeno-associated virus (rAAV)-mediated gene therapy, an intein-split cytosine base editor (BE4max) was developed. BE4max efficiently induced C-to-T conversion and restored the start codon to ameliorate HT1 in mice, but an undesired bystander mutation abolished the effect of on-target editing. To solve this problem, an upstream sequence was targeted to generate a de novo in-frame start codon to initiate the translation of FAH. After treatment, almost all C-to-T conversions created a start codon and restored Fah expression, which efficiently ameliorated the disease without inducing off-target mutations. Our study demonstrated that base editing-mediated creation of de novo functional elements would be an applicable new strategy for genetic disease therapy.

Cas9-nickase-mediated genome editing corrects hereditary tyrosinemia in rats.

Hereditary tyrosinemia type I (HTI) is a metabolic genetic disorder caused by mutation of fumarylacetoacetate hydrolase (FAH). Because of the accumulation of toxic metabolites, HTI causes severe liver cirrhosis, liver failure, and even hepatocellular carcinoma. HTI is an ideal model for gene therapy, and several strategies have been shown to ameliorate HTI symptoms in animal models. Although CRISPR/Cas9-mediated genome editing is able to correct the Fah mutation in mouse models, WT Cas9 induces numerous undesired mutations that have raised safety concerns for clinical applications. To develop a new method for gene correction with high fidelity, we generated a Fah mutant rat model to investigate whether Cas9 nickase (Cas9n)-mediated genome editing can efficiently correct the Fah First, we confirmed that Cas9n rarely induces indels in both on-target and off-target sites in cell lines. Using WT Cas9 as a positive control, we delivered Cas9n and the repair donor template/single guide (sg)RNA through adenoviral vectors into HTI rats. Analyses of the initial genome editing efficiency indicated that only WT Cas9 but not Cas9n causes indels at the on-target site in the liver tissue. After receiving either Cas9n or WT Cas9-mediated gene correction therapy, HTI rats gained weight steadily and survived. Fah-expressing hepatocytes occupied over 95% of the liver tissue 9 months after the treatment. Moreover, CRISPR/Cas9-mediated gene therapy prevented the progression of liver cirrhosis, a phenotype that could not be recapitulated in the HTI mouse model. These results strongly suggest that Cas9n-mediated genome editing is a valuable and safe gene therapy strategy for this genetic disease.

Virus-Triggered ATP Release Limits Viral Replication through Facilitating IFN-ß Production in a P2X7-Dependent Manner.

Accumulating evidence shows that innate immune responses are associated with extracellular nucleotides, particularly ATP. In this article, we demonstrate extensive protection of ATP/P2X7 signaling in a host against viral infection. Interestingly, we observed a significant increase in ATP as a danger signal in vesicular stomatitis virus (VSV)-infected cell supernatant and VSV-infected mice in an exocytosis- and pannexin channel-dependent manner. Furthermore, extracellular ATP reduces the replication of VSV, Newcastle disease virus, murine leukemia virus, and HSV in vivo and in vitro through the P2X7 receptor. Meanwhile, ATP significantly increases IFN-ß expression in a concentration- and time-dependent manner. Mechanistically, ATP facilitates IFN-ß secretion through P38/JNK/ATF-2 signaling pathways, which are crucial in promoting antiviral immunity. Taken together, these results demonstrate the protective role of extracellular ATP and P2X7 in viral infection and suggest a potential therapeutic role for ATP/P2X7 in viral diseases.

Leucine-rich repeat-containing G protein-coupled receptor 4 facilitates vesicular stomatitis virus infection by binding vesicular stomatitis virus glycoprotein.

Vesicular stomatitis virus (VSV) and rabies and Chandipura viruses belong to the Rhabdovirus family. VSV is a common laboratory virus to study viral evolution and host immune responses to viral infection, and recombinant VSV-based vectors have been widely used for viral oncolysis, vaccination, and gene therapy. Although the tropism of VSV is broad, and its envelope glycoprotein G is often used for pseudotyping other viruses, the host cellular components involved in VSV infection remain unclear. Here, we demonstrate that the host protein leucine-rich repeat-containing G protein-coupled receptor 4 (Lgr4) is essential for VSV and VSV-G pseudotyped lentivirus (VSVG-LV) to infect susceptible cells. Accordingly, Lgr4-deficient mice had dramatically decreased VSV levels in the olfactory bulb. Furthermore, Lgr4 knockdown in RAW 264.7 cells also significantly suppressed VSV infection, and Lgr4 overexpression in RAW 264.7 cells enhanced VSV infection. Interestingly, only VSV infection relied on Lgr4, whereas infections with Newcastle disease virus, influenza A virus (A/WSN/33), and herpes simplex virus were unaffected by Lgr4 status. Of note, assays of virus entry, cell ELISA, immunoprecipitation, and surface plasmon resonance indicated that VSV bound susceptible cells via the Lgr4 extracellular domain. Pretreating cells with an Lgr4 antibody, soluble LGR4 extracellular domain, or R-spondin 1 blocked VSV infection by competitively inhibiting VSV binding to Lgr4. Taken together, the identification of Lgr4 as a VSV-specific host factor provides important insights into understanding VSV entry and its pathogenesis and lays the foundation for VSV-based gene therapy and viral oncolytic therapeutics.

Lgr4/Gpr48 negatively regulates TLR2/4-associated pattern recognition and innate immunity by targeting CD14 expression.

The recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is pivotal in both innate and adaptive immune responses. Here we demonstrate that deletion of Lgr4/Gpr48 (G-protein-coupled receptor 48), a seven-transmembrane glycoprotein hormone receptor, potentiates TLR2/4-associated cytokine production and attenuates mouse resistance to septic shock. The expression of CD14, a co-receptor for TLR2/4-associated pathogen-associated molecular patterns, is increased significantly in Lgr4-deficient macrophages, which is consistent with the increased immune response, whereas the binding activity of cAMP-response element-binding protein is decreased significantly in Lgr4-deficient macrophages, which up-regulate the expression of CD14 at the transcriptional level. Together, our data demonstrate that Lgr4/Gpr48 plays a critical role in modulating the TLR2/4 signaling pathway and represents a useful therapeutic approach of targeting Lgr4/Gpr48 in TLR2/4-associated septic shock and autoimmune diseases.

Impact of Nicosulfuron on Sperm Quality: Insights into Testicular Cell Apoptosis and NF-κB Signaling Pathway in Mice Testes.

BACKGROUND: Nicosulfuron, a widely used herbicide in crops, has raised concerns due to its escalating presence as an environmental pollutant, particularly in soil and water. The potential adverse effects of nicosulfuron on animals, including reproductive toxicity, have garnered attention. OBJECTIVE: The study aimed to evaluate the reproductive toxicity of nicosulfuron in male mice. METHODS: Male mice were orally administrated with three different concentration gradients (350, 700, and 1400 mg/kg) of nicosulfuron for 35 days. The investigation delved into sperm quality, testicular structures, and expression of cleaved caspase-3 and NF-κB p65 of the testes. RESULTS: The finding unveiled a correlation between nicosulfuron exposure and detrimental effects on sperm quality and alteration of testicular structure. Notably, parameters, such as sperm survival rate (SUR) and sperm motility (MOT), exhibited a decline in relation to increasing nicosulfuron dosages. Moreover, in the mice subjected to higher doses of nicosulfuron, elevated expression of cleaved caspase-3 and NF-κB p65 was observed in the testes. Interestingly, we also observed an increase of NF-κB p65 expression in the mice exposed to the nicosulfuron. CONCLUSION: Our research revealed that exposure to nicosulfuron resulted in compromised sperm quality and alterations in testicular structure. The correlation between nicosulfuron and apoptosis, especially via the NF-κB pathway, provided significant insights into the mechanisms underpinning these detrimental effects. These findings significantly enhance our comprehension of the potential hazards associated with nicosulfuron exposure and its impacts on the reproductive health of animals.

Enhanced genome editing to ameliorate a genetic metabolic liver disease through co-delivery of adeno-associated virus receptor.

Genome editing through adeno-associated viral (AAV) vectors is a promising gene therapy strategy for various diseases, especially genetic disorders. However, homologous recombination (HR) efficiency is extremely low in adult animal models. We assumed that increasing AAV transduction efficiency could increase genome editing activity, especially HR efficiency, for in vivo gene therapy. Firstly, a mouse phenylketonuria (PKU) model carrying a pathogenic R408W mutation in phenylalanine hydroxylase (Pah) was generated. Through co-delivery of the general AAV receptor (AAVR), we found that AAVR could dramatically increase AAV transduction efficiency in vitro and in vivo. Furthermore, co-delivery of SaCas9/sgRNA/donor templates with AAVR via AAV8 vectors increased indel rate over 2-fold and HR rate over 15-fold for the correction of the single mutation in PahR408W mice. Moreover, AAVR co-injection successfully increased the site-specific insertion rate of a 1.4 kb Pah cDNA by 11-fold, bringing the HR rate up to 7.3% without detectable global off-target effects. Insertion of Pah cDNA significantly decreased the Phe level and ameliorated PKU symptoms. This study demonstrates a novel strategy to dramatically increase AAV transduction which substantially enhanced in vivo genome editing efficiency in adult animal models, showing clinical potential for both conventional and genome editing-based gene therapy.

Increasing the efficiency and targeting range of cytidine base editors through fusion of a single-stranded DNA-binding protein domain.

Cytidine base editors are powerful genetic tools that catalyse cytidine to thymidine conversion at specific genomic loci, and further improvement of the editing range and efficiency is critical for their broader applications. Through insertion of a non-sequence-specific single-stranded DNA-binding domain from Rad51 protein between Cas9 nickase and the deaminases, serial hyper cytidine base editors were generated with substantially increased activity and an expanded editing window towards the protospacer adjacent motif in both cell lines and mouse embryos. Additionally, hyeA3A-BE4max selectively catalysed cytidine conversion in TC motifs with a broader editing range and much higher activity (up to 257-fold) compared with eA3A-BE4max. Moreover, hyeA3A-BE4max specifically generated a C-to-T conversion without inducing bystander mutations in the haemoglobin gamma gene promoter to mimic a naturally occurring genetic variant for amelioration of ß-haemoglobinopathy, suggesting the therapeutic potential of the improved base editors.

Dual base editor catalyzes both cytosine and adenine base conversions in human cells.

Although base editors are useful tools for precise genome editing, current base editors can only convert either adenines or cytosines. We developed a dual adenine and cytosine base editor (A&C-BEmax) by fusing both deaminases with a Cas9 nickase to achieve C-to-T and A-to-G conversions at the same target site. Compared to single base editors, A&C-BEmax's activity on adenines is slightly reduced, whereas activity on cytosines is higher and RNA off-target activity is substantially decreased.

Correction to: Increasing targeting scope of adenosine base editors in mouse and rat embryos through fusion of TadA deaminase with Cas9 variants.

In the original publication the grant number is incorrectly published. The correct grant number should be read as "17140901600". The corrected contents are provided in this correction article. This work was partially supported by grants from the National Natural Science Foundation of China (Nos. 81670470 and 81600149), a grant from the Shanghai Municipal Commission for Science and Technology (17140901600, 18411953500 and 15JC1400201) and a grant from National Key Research and Development Program (2016YFC0905100).

Kisspeptin/GPR54 signaling restricts antiviral innate immune response through regulating calcineurin phosphatase activity.

G protein-coupled receptor 54 (GPR54), the key receptor for the neuropeptide hormone kisspeptin, plays essential roles in regulating puberty development and cancer metastasis. However, its role in the antiviral innate immune response is unknown. We report that virus-induced type I interferon (IFN-I) production was significantly enhanced in Gpr54-deficient cells and mice and resulted in restricted viral replication. We found a marked increase of kisspeptin in mouse serum during viral infection, which, in turn, impaired IFN-I production and antiviral immunity through the GPR54/calcineurin axis. Mechanistically, kisspeptin/GPR54 signaling recruited calcineurin and increased its phosphatase activity to dephosphorylate and deactivate TANK [tumor necrosis factor receptor-associated factor (TRAF) family member-associated NF-κB activator]-binding kinase 1 (TBK1) in a Ca2+-dependent manner. Thus, our data reveal a kisspeptin/GPR54/calcineurin-mediated immune evasion pathway exploited by virus through the negative feedback loop of TBK1 signaling. These findings also provide insights into the function and cross-talk of kisspeptin, a known neuropeptide hormone, in antiviral innate immune response.

Inhibition of Rspo-Lgr4 Facilitates Checkpoint Blockade Therapy by Switching Macrophage Polarization.

Therapies targeting immune checkpoints have shown great clinical potential in a subset of patients with cancer but may be hampered by a failure to reverse the immunosuppressive tumor microenvironment (TME). As the most abundant immune cells in TME, tumor-associated macrophages (TAM) play nonredundant roles in restricting antitumor immunity. The leucine-rich repeat-containing G-protein-coupled receptor 4 (Lgr4, also known as Gpr48) has been associated with multiple physiologic and pathologic functions. Lgr4 and its ligands R-spondin 1-4 have been shown to promote the growth and metastasis of tumor cells. However, whether Lgr4 can promote tumor progression by regulating the function of immune cells in the tumor microenvironment remains largely unknown. Here, we demonstrate that Lgr4 promotes macrophage M2 polarization through Rspo/Lgr4/Erk/Stat3 signaling. Notably, urethane-induced lung carcinogenesis, Lewis lung carcinoma (LLC), and B16F10 melanoma tumors were all markedly reduced in Lgr4fl/flLyz2cre/+ mice, characterized by fewer protumoral M2 TAMs and increased CD8+ T lymphocyte infiltration in the TME. Furthermore, LLC tumor growth was greatly depressed when Rspo/Lgr4/Erk/Stat3 signaling was blocked with either the LGR4 extracellular domain or an anti-Rspo1 antibody. Importantly, blocking Rspo-Lgr4 signaling overcame LLC resistance to anti-PD-1 therapy and improved the efficacy of PD-1 immunotherapy against B16F10 melanoma, indicating vital roles of Rspo-Lgr4 in host antitumor immunity and a potential therapeutic target in cancer immunotherapy.Significance: This study identifies a novel receptor as a critical switch in TAM polarization whose inhibition sensitizes checkpoint therapy-resistant lung cancer to anti-PD-1 therapy.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/17/4929/F1.large.jpg Cancer Res; 78(17); 4929-42. ©2018 AACR.

Metabolite-Sensing G Protein Coupled Receptor TGR5 Protects Host From Viral Infection Through Amplifying Type I Interferon Responses.

The metabolite-sensing G protein-coupled receptors (GPCRs) bind to various metabolites and transmit signals that are important for proper immune and metabolic functions. However, the roles of metabolite-sensing GPCRs in viral infection are not well characterized. Here, we identified metabolite-sensing GPCR TGR5 as an interferon (IFN)-stimulated gene (ISG) which had increased expression following viral infection or IFN-ß stimulation in a STAT1-dependent manner. Most importantly, overexpression of TGR5 or treatment with the modified bile acid INT-777 broadly protected host cells from vesicular stomatitis virus (VSV), newcastle disease virus (NDV) and herpes simplex virus type 1 (HSV-1) infection. Furthermore, VSV and HSV-1 replication was increased significantly in Tgr5-deficient macrophages and the VSV distribution in liver, spleen and lungs was increased in Tgr5-deficient mice during VSV infection. Accordingly, Tgr5-deficient mice were much more susceptible to VSV infection than wild-type mice. Mechanistically, TGR5 facilitates type I interferon (IFN-I) production through the AKT/IRF3-signaling pathway, which is crucial in promoting antiviral innate immunity. Taken together, our data reveal a positive feedback loop regulating IRF3 signaling and suggest a potential therapeutic role for metabolite-sensing GPCRs in controlling viral diseases.

CRISPR/Cas9-mediated somatic correction of a novel coagulator factor IX gene mutation ameliorates hemophilia in mouse.

The X-linked genetic bleeding disorder caused by deficiency of coagulator factor IX, hemophilia B, is a disease ideally suited for gene therapy with genome editing technology. Here, we identify a family with hemophilia B carrying a novel mutation, Y371D, in the human F9 gene. The CRISPR/Cas9 system was used to generate distinct genetically modified mouse models and confirmed that the novel Y371D mutation resulted in a more severe hemophilia B phenotype than the previously identified Y371S mutation. To develop therapeutic strategies targeting this mutation, we subsequently compared naked DNA constructs versus adenoviral vectors to deliver Cas9 components targeting the F9 Y371D mutation in adult mice. After treatment, hemophilia B mice receiving naked DNA constructs exhibited correction of over 0.56% of F9 alleles in hepatocytes, which was sufficient to restore hemostasis. In contrast, the adenoviral delivery system resulted in a higher corrective efficiency but no therapeutic effects due to severe hepatic toxicity. Our studies suggest that CRISPR/Cas-mediated in situ genome editing could be a feasible therapeutic strategy for human hereditary diseases, although an efficient and clinically relevant delivery system is required for further clinical studies.