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Background Clustered, regularly interspaced, short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) have recently opened a new avenue for gene therapy. Cas9 nuclease guided by a single-guide RNA (sgRNA) has been extensively used for genome editing. Currently, three Cas9 orthologs have been adapted for in vivo genome engineering applications: Streptococcus pyogenes Cas9 (SpyCas9), Staphylococcus aureus Cas9 (SauCas9), and Campylobacter jejuni (CjeCas9). However, additional in vivo editing platforms are needed, in part to enable a greater range of sequences to be accessed via viral vectors, especially those in which Cas9 and sgRNA are combined into a single vector genome. Results Here, we present in vivo editing using Neisseria meningitidis Cas9 (NmeCas9). NmeCas9 is compact, edits with high accuracy, and possesses a distinct protospacer adjacent motif (PAM), making it an excellent candidate for safe gene therapy applications. We find that NmeCas9 can be used to target the Pcsk9 and Hpd genes in mice. Using tail-vein hydrodynamic-based delivery of NmeCas9 plasmid to target the Hpd gene, we successfully reprogram the tyrosine degradation pathway in Hereditary Tyrosinemia Type I mice. More importantly, we deliver NmeCas9 with its sgRNA in a single recombinant adeno-associated vector (rAAV) to target Pcsk9 , resulting in lower cholesterol levels in mice. This all-in-one vector yielded > 35% gene modification after two weeks of vector administration, with minimal off-target cleavage in vivo. Conclusions Our findings indicate that NmeCas9 can enable the editing of disease-causing loci in vivo, expanding the targeting scope of RNA-guided nucleases.

Efficient Cas9 genome editing in vivo is achieved without viral vectors using chemically modified single-guide RNAs. Efficient genome editing with Cas9–sgRNA in vivo has required the use of viral delivery systems, which have limitations for clinical applications. Translational efforts to develop other RNA therapeutics have shown that judicious chemical modification of RNAs can improve therapeutic efficacy by reducing susceptibility to nuclease degradation. Guided by the structure of the Cas9–sgRNA complex, we identify regions of sgRNA that can be modified while maintaining or enhancing genome-editing activity, and we develop an optimal set of chemical modifications for in vivo applications. Using lipid nanoparticle formulations of these enhanced sgRNAs (e-sgRNA) and mRNA encoding Cas9, we show that a single intravenous injection into mice induces >80% editing of Pcsk9 in the liver. Serum Pcsk9 is reduced to undetectable levels, and cholesterol levels are significantly lowered about 35% to 40% in animals. This strategy may enable non-viral, Cas9-based genome editing in the liver in clinical settings.

CRISPR/Cas genome editing is a simple, cost effective, and highly specific technique for introducing genetic variations. In mammalian cells, CRISPR/Cas can facilitate non-homologous end joining, homology- directed repair, and single-base exchanges. Cas9/Cas12a nuclease, dCas9 transcriptional regulators, base editors, PRIME editors and RNA editing tools are widely used in basic research. Currently, a variety of CRISPR/Cas-based therapeutics are being investigated in clinical trials. Among many new findings that have advanced the field, we highlight a few recent advances that are relevant to CRISPR/Cas-based gene therapies for monogenic human genetic diseases.

Background: Hepatocellular carcinoma (HCC) is characterized by a poor prognosis and accounts for the fourth common cause of cancer-related deaths. Recently, pyroptosis has been revealed to be involved in the progression of multiple cancers. However, the role of pyroptosis in the HCC prognosis remains elusive. Methods: The clinical information and RNA-seq data of the HCC patients were collected from the TCGA-LIHC datasets, and the differential pyroptosis-related genes (PRG) were firstly explored. The univariate Cox regression and consensus clustering were applied to recognize the HCC subtypes. The prognostic PRGs were then submitted to the LASSO regression analysis to build a prognostic model in the TCGA training cohort. We further evaluated the predictive model in the TCGA test cohort and ICGC validation cohort (LIRI-JP). The accuracy of prediction was validated using the Kaplan—Meier (K-M) and receiver operating characteristic (ROC) analyses. The single-sample gene set enrichment analysis (ssGSEA) was used to determine the differential immune cell infiltrations and related pathways. Finally, the expression of the prognostic genes was validated by qRT-PCR in vivo and in vitro . Results: We identified a total of 26 differential PRGs, among which three PRGs comprising GSDME, GPX4, and SCAF11 were subsequently chosen for constructing a prognostic model. This model significantly distinguished the HCC patients with different survival years in the TCGA training, test, and ICGC validation cohorts. The risk score of this model was confirmed as an independent prognostic factor. A nomogram was generated indicating the survival years for each HCC patient. The ssGSEA demonstrated several tumor-infiltrating immune cells to be remarkably associated with the risk scores. The qRT-PCR results also showed the apparent dysregulation of PRGs in HCC. Finally, the drug sensitivity was analyzed, indicating that Lenvatinib might impact the progression of HCC via targeting GSDME, which was also validated in human Huh7 cells. Conclusion: The PRG signature comprised of GSDME, GPX4, and SCAF11 can serve as an independent prognostic factor for HCC patients, which would provide further evidence for more clinical and functional studies.

Cas9-mediated gene editing corrects hereditary tyrosinemia in a mouse model. The combination of Cas9, guide RNA and repair template DNA can induce precise gene editing and the correction of genetic diseases in adult mammals. However, clinical implementation of this technology requires safe and effective delivery of all of these components into the nuclei of the target tissue. Here, we combine lipid nanoparticle–mediated delivery of Cas9 mRNA with adeno-associated viruses encoding a sgRNA and a repair template to induce repair of a disease gene in adult animals. We applied our delivery strategy to a mouse model of human hereditary tyrosinemia and show that the treatment generated fumarylacetoacetate hydrolase (Fah)-positive hepatocytes by correcting the causative Fah-splicing mutation. Treatment rescued disease symptoms such as weight loss and liver damage. The efficiency of correction was >6% of hepatocytes after a single application, suggesting potential utility of Cas9-based therapeutic genome editing for a range of diseases.

Diseases caused by different mutations in the two alleles of a gene are treated in mice by Cas-9-induced allelic exchange. We report a genome-editing strategy to correct compound heterozygous mutations, a common genotype in patients with recessive genetic disorders. Adeno-associated viral vector delivery of Cas9 and guide RNA induces allelic exchange and rescues the disease phenotype in mouse models of hereditary tyrosinemia type I and mucopolysaccharidosis type I. This approach recombines non-mutated genetic information present in two heterozygous alleles into one functional allele without using donor DNA templates.

Hepatocellular carcinoma (HCC) is clinically distinguished by its covert onset, rapid progression, high recurrence rate, and poor prognosis. Studies have revealed that SETDB1 (SET Domain Bifurcated 1) is a histone H3 methyltransferase located on chromosome 1 and plays a crucial role in carcinogenesis. Therefore, we aimed to evaluate the clinical significance of SETDB1 expression in HCC. In patients with HCC, elevated levels of SETDB1 correlated with a poorer overall survival (OS) rate, marking it as an independent prognostic factor for HCC, as revealed by both univariate and multivariate Cox analyses. Furthermore, we utilized the SangerBox and TISIDB databases to profile the tumor immune microenvironment in HCC, including scoring the tumor microenvironment and assessing immune cell infiltration. The TIDE algorithm was employed to examine the association between SETDB1 expression and immune responses. Our findings indicated that SETDB1 expression negatively correlated with the majority of immune cells, a wide range of immune cell marker genes, and numerous immune pathways, thereby leading to the reduced effectiveness of immune checkpoint inhibitors. Lastly, both in vivo and ex vivo experiments were conducted to substantiate the role of SETDB1 in HCC tumorigenesis. In conclusion, the upregulation of SETDB1 is associated with a poorer prognosis in HCC patients and inversely correlates with immune cell infiltration, potentially serving as a predictive marker for immunotherapy response.

In Caenorhabditis elegans , mitochondrial activity as measured by the frequency of the mitochondrial flash in young adult animals is a powerful predictor of lifespan across genetic, environmental and stochastic factors. Mitoflash activity tests ageing theory The mitochondrial theory of ageing, developed more than 40 years ago based on work on the roundworm Caenorhabditis elegans , proposes that the mitochondria are the main drivers of ageing — defined as an increase in the probability of death with increasing chronological age. This study is a direct test of the theory using an approach made possible by the recent demonstration that mitochondria undergo stochastic bursts of superoxide production that can be visualized as mitochondrial flashes. The flash frequency of these 'mitoflashes' is sensitive to oxidative stress and metabolic changes. The authors observe that mitoflash activity in the pharyngeal muscles of a 3-day-old adult C. elegans worm inversely correlates with lifespan of the animal. A large variety of genetic mutations and environmental factors inversely modify the lifespan and the mitoflash frequency at day 3. Even within an isogenic population of worms the day-3 mitoflash frequency negatively correlates with lifespan. Day-3 mitoflash frequency is shown to be a powerful predictor of C. elegans lifespan reflecting a range of genetic and environmental influences, suggesting an intimate connection between mitochondrial function and ageing. It has been theorized for decades that mitochondria act as the biological clock of ageing 1 , but the evidence is incomplete. Here we show a strong coupling between mitochondrial function and ageing by in vivo visualization of the mitochondrial flash (mitoflash), a frequency-coded optical readout reflecting free-radical production and energy metabolism at the single-mitochondrion level 2 , 3 . Mitoflash activity in Caenorhabditis elegans pharyngeal muscles peaked on adult day 3 during active reproduction and on day 9 when animals started to die off. A plethora of genetic mutations and environmental factors inversely modified the lifespan and the day-3 mitoflash frequency. Even within an isogenic population, the day-3 mitoflash frequency was negatively correlated with the lifespan of individual animals. Furthermore, enhanced activity of the glyoxylate cycle contributed to the decreased day-3 mitoflash frequency and the longevity of daf-2 mutant animals. These results demonstrate that the day-3 mitoflash frequency is a powerful predictor of C. elegans lifespan across genetic, environmental and stochastic factors. They also support the notion that the rate of ageing, although adjustable in later life, has been set to a considerable degree before reproduction ceases.

Background Mood instability, characterized by sudden and unpredictable mood shifts, is prevalent in psychiatric disorders and as a personality trait. Its association with gastrointestinal diseases has been recognized but remains poorly understood in terms of causality. Methods This study aims to investigate the causal relationship between mood instability and a spectrum of gastrointestinal diseases by univariable and multivariable mendelian randomization analysis. The exposure and outcome data were retrieved from the IEU open GWAS database, the UK biobank and the FinnGen study. Instrumental variables were selected to meet relevance, independence, and exclusion restriction criteria. GWAS datasets for mood instability and 28 gastrointestinal diseases were utilized, incorporating diverse populations and genders. Univariable and multivariable Mendelian randomization analyses were conducted using R software. MR statistics from different datasets for the same disease were meta-analyzed to maximize the study population. Results In univariable MR analysis, genetic predisposition to mood instability showed significant associations with increased risk for several gastrointestinal diseases, including: gastroesophageal reflux disease, gastric ulcer, acute gastritis, irritable bowel syndrome, internal hemorrhoids, cirrhosis, cholecystitis, cholelithiasis, acute pancreatitis, chronic pancreatitis. In multivariable MR analysis, after adjusting for major depression, bipolar disorder, anxiety disorder, and schizophrenia, associations with the following gastrointestinal diseases remained statistically significant: internal hemorrhoids, cirrhosis, acute pancreatitis, chronic pancreatitis. Conclusion This study provides compelling evidence for a potential causal relationship between mood instability and certain gastrointestinal diseases underscoring the importance of considering mood instability as a potential risk factor for gastrointestinal diseases as well as the positive role of maintaining mood stability in the prevention of gastrointestinal disorders.

CRISPR is widely used to disrupt gene function by inducing small insertions and deletions. Here, we show that some single-guide RNAs (sgRNAs) can induce exon skipping or large genomic deletions that delete exons. For example, CRISPR-mediated editing of β-catenin exon 3, which encodes an autoinhibitory domain, induces partial skipping of the in-frame exon and nuclear accumulation of β-catenin. A single sgRNA can induce small insertions or deletions that partially alter splicing or unexpected larger deletions that remove exons. Exon skipping adds to the unexpected outcomes that must be accounted for, and perhaps taken advantage of, in CRISPR experiments.