Biological: CRISPR/Cas
β-Thalassaemia, a hereditary hemolytic anemia disease, is one of the most common and health-threatening monogenic diseases in the world. It is characterized by mutations in the β-globin (HBB) gene, leading to severe anemia caused by decreased hemoglobin (Hb) level [161] . For the moment, the only way to cure β-thalassemia is hematopoietic stem cell transplantation (HSCT). Yet, high cost of treatment and shortage of donors limit its clinical application [162] . Other therapy, for example, blood transfusion, can only sustain the life of patients but can’t cure the disease [161] . To better treat β-thalassemia, researchers have turned their attention to gene therapy. A major technical idea is to repair the defective β-globin gene of iPSCs from patients with β-thalassemia by CRISPR-Cas9 technology, then red blood cells can be produced normally and the disease could be cured [163] , [164] . Besides, reactivating fetal hemoglobin (HbF) expression has also been proposed to be an effective method to treat β-thalassemia through knockout of BCL11A gene, which suppresses the expression of fetal hemoglobin [165] , [166] .
Additionally, CRISPR-Cas systems have also been used for the treatment of other hematologic diseases, such as sickle cell disease (SCD) and hemophilia B (HB). SCD is a monogenic disease caused by a single-nucleotide mutation in human β-globin gene, leading to a substitution of glutamic acid by valine and the production of an abnormal version of β-globin, which is known as hemoglobin S (HbS) [167] . CRISPR-Cas9 system has been used to treat SCD by repairing the β-globin gene mutation or reactivating HbF expression [168] , [169] . HB is an X-linked hereditary bleeding disorder caused by deficiency of coagulation factor IX, and the most common treatment for hemophilia B is supplement blood coagulation factor [170] , [171] . Huai et al. injected naked Cas9-sgRNA plasmid and donor DNA into the adult mice of F9 mutation HB mouse model for gene correction [172] . Meanwhile, Cas9/sgRNA were also microinjected into germline cells of this HB mouse model for gene correction. Both in vivo and ex vivo experiment were sufficient to remit the coagulation deficiency [172] . Guan et al. corrected the F9 Y371D mutation in HB mice using CRISPR-Cas9 mediated in situ genome editing, which greatly improved the hemostatic efficiency and increased the survival of HB mice [173] .
Duchenne muscular dystrophy (DMD) is an X-chromosome recessive hereditary disease, with clinical manifestations of muscle weakness or muscle atrophy due to a progressive deterioration of skeletal muscle function [174] . It is usually caused by mutations in the DMD gene, a gene encoding dystrophin protein [174] . Deletions of one or more exons of the DMD gene will result in frameshift mutations or premature termination of translation, thereby normal dystrophin protein can not be synthesized [175] . Currently, there is no effective treatment for DMD. Conventional drug treatment can only control the disease to a certain extent, but can not cure it. It was found that a functional truncated dystrophin protein can be obtained by removing the mutated transcripts with CRISPR-Cas9 system [176] , [177] , [178] . In addition, base editing systems can also be applied in DMD treatment by repairing single base mutation or inducing exon skipping by introducing premature termination codons (PTCs) [179] .
Retinitis pigmentosa (RP) is a group of hereditary retinal degenerative diseases characterized by progressive loss of photoreceptor cells and retinal pigment epithelium (RPE) function [180] . RP has obvious genetic heterogeneity, and the inheritance patterns include autosomal dominant, autosomal recessive, and X-linked recessive inheritance [180] . To date, there is still no cure for RP. In recent years, with the rapid development of gene editing technology, there has been some progress in the treatment of RP. Several gene mutations causing RP have been corrected by CRISPR-Cas9 in mouse models to prevent retinal degeneration and improve visual function, for example, RHO gene, PRPF31 gene and RP1 gene [181] , [182] .
Leber Congenital Amaurosis type 10 (LCA10) is an autosomal retinal dystrophy with severe vision loss at an early age. The most common gene mutation found in patients with LCA10 is IVS26 mutation in the CEP290 gene, which disrupts the coding sequence by generating an aberrant splice site [183] . Ruan et al. used CRISPR-Cas9 system to knock out the intronic region of the CEP290 gene and restored normal CEP290 expression [184] . In addition, subretinal injection of EDIT-101 in humanized CEP290 mice showed rapid and sustained CEP290 gene editing [185] , [186] .
Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare lethal genetic disorder with the characteristic of accelerated aging [187] . A point mutation within exon 11 of lamin A gene activates a cryptic splice site, leading to the production of a truncated lamin A called progerin [188] . However, CRISPR-Cas based gene therapy has opened up a broad prospect in HGPS treatment. Administration of AAV-delivered CRISPR-Cas9 components into HGPS mice can reduce the expression of progerin, thereby improved the health condition and prolonged the lifespan of HGPS mice [189] , [190] . In addition, Suzuki et al . repaired G609G mutation in a HGPS mouse model via single homology arm donor mediated intron-targeting gene integration (SATI), which ameliorated aging-associated phenotypes and extended the lifespan of HGPS mice [191] .
CRISPR-Cas systems have also showed their advantages in gene therapy of hereditary tyrosinemia (HT) and cystic fibrosis (CF). HT is a disorder of tyrosine metabolism caused by deficiency of fuarylacetoacetate hydrolase (Fah) [192] . Yin et al. corrected a Fah mutation in a HT mouse model by injecting CRISPR-Cas9 components into the liver of the mice [193] . Then, the wild-type Fah protein in the liver cells began to express and the body weight loss phenotype was rescued [193] . CF, an autosomal recessive inherited disease with severe respiratory problems and infections, has a high mortality rate at an early age [194] . It is caused by mutations in the CFTR gene, which encodes an epithelial chloride anion channel, the cystic fibrosis transmembrane conductance regulator (CFTR) [194] . Until now, genome editing strategies have been carried out in cell models to correct CFTR mutations. In cultured intestinal stem cells and induced pluripotent stem cells from cystic fbrosis patients, the CFTR homozygous Δ508 mutation has been corrected by CRISPR-Cas9 technology, leading to recovery of normal CFTR expression and function in differentiated mature airway epithelial cells and intestinal organoids [195] , [196] .
In recent years, gene therapy has gradually been applied to the treatment of viral infectious diseases. Transforming host cells to avoid viral infection or preventing viral proliferation and transmission are two main strategies for gene therapy of viral infectious diseases [197] .
Human immunodeficiency virus (HIV), a kind of retrovirus, mainly attacks the human immune system, especially the CD4 + T lymphocytes. When human cells are invaded by HIV, the viral sequences can be integrated into the host genome, blocking cellular and humoral immunity while causing acquired immunodeficiency syndrome (AIDS) [198] . There is still no known cure for AIDS but it could be treated. Although antiretroviral therapy can inhibit HIV-1 replication, the viral sequences still exist in the host genome, and they could be reactivated at any time [199] . CRISPR-Cas9 system can target long terminal repeat (LTR) and destruct HIV-1 proviruses, thus it is possible to completely eliminate HIV-1 from genome of infected host cells [200] , [201] . In addition, resistance to HIV-1 infection could be induced by knockout of the HIV co-receptor CCR5 gene in CD4 + T cells [202] , [203] .
Cervical cancer is the second most common gynecologic malignant tumor. The incidence is increasing year by year and young people are especially prone to this disease. It was found that the occurrence of cervical cancer is closely related to HPV (human papillomavirus) infection [204] . HPV is a double-stranded cyclic DNA virus, E6 and E7 genes located in HPV16 early regions are carcinogenic genes [205] . Researchers designed sgRNAs targeting E6 and E7 genes to block the expression of E6 and E7 protein, subsequently the expression of p53 and pRb was restored to normal, finally increasing tumor cells apoptosis and suppressing subcutaneous tumor growth in in vivo experiments [206] , [207] , [208] . Moreover, HPV virus proliferation was blocked through cutting off E6/E7 genes, and the virus in the bodies could be eliminated [206] , [207] , [208] .
Cancer is the second leading cause of death worldwide after cardiovascular diseases, and it is also a medical problem that needs to be solved urgently. A variety of genetic or epigenetic mutations have been accumulated in the cancer genome, which can activate proto-oncogenes, inactivate tumor suppressors and produce drug resistance [209] , [210] . So far, CRISPR-Cas systems have been used to correct the oncogenic genome/epigenome mutations in tumor cells and animal models, resulting in inhibition of tumor cell growth and promotion of cell apoptosis, thereby inhibiting tumor growth [211] , [212] , [213] .
In addition, immunotherapy is considered to be a major breakthrough in cancer treatment, especially chimeric antigen receptor-T (CAR-T) cell therapy, which has a significantly therapeutic effect on leukemia, lymphoma and certain types of solid tumors [214] , [215] , [216] . CAR-T cells are genetically manipulated, patient-specific T cells, which express receptors targeting antigens specially expressed on tumor cells, for example, CD19 CAR-T cells for B cell malignancies. Then these cells will be transfused back to patients to fight against cancer [217] . However, CAR-T cell therapy is complex, time-consuming and expensive, and it is greatly limited by the quality and quantity of autologous T cells. Therefore, researchers have used CRISPR-Cas9 system to develop universal CAR-T cells, such as simultaneously removing endogenous T cell receptor gene and HLA class I encoding gene on T cells of healthy donors and introducing CAR sequence [218] , [219] , [220] . Thereby, it could be used in multiple patients without causing graft versus host reaction (GVHR). In addition, CRISPR-Cas mediated genome editing has also been used to enhance the function of CAR-T cells by knocking out genes encoding signaling molecules or T cell inhibitory receptors, such as programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA-4) [221] , [222] .
Though CRISPR-Cas mediated efficient genome editing technologies have been broadly applied in a variety of species and different types of cells, there are still some important issues needed to be addressed during the process of application, such as off-target effects, delivery methods, immunogenicity and potential risk of cancer.
It was found that designed sgRNAs will mismatch with non-target DNA sequences and introduce unexpected gene mutations, called off-target effects [223] . Off-target effects seriously restrict the widespread application of CRISPR-Cas mediated genome editing in gene therapy, for it might lead to genomic instability and increase the risk of certain diseases by introducing unwanted mutations at off-target sites [224] . At present, several strategies have been used to predict and detect off-target effects, online prediction software, whole genome sequencing (WGS), genome-wide, unbiased identification of DSBs enabled by sequencing (GUIDE-seq), discovery of in situ cas off-targets and verification by sequencing (DISCOVER-Seq), etc [225] . Furthermore, to minimize off-target effects, researchers have systematically studied the factors affecting off-target effects and developed a number of effective approaches.
The specific binding of sgRNA with the target sequence is the key factor in CRISPR-Cas mediated genome editing. Rational design of highly specific sgRNAs might minimize off-target effects [224] . The length and GC content of sgRNAs, and mismatches between sgRNA and its off-target site will all affect the frequency of off-target effects [226] . In addition, on the basis of rational design of sgRNAs, the specificity of CRISPR-Cas systems can be further improved by modifying sgRNAs, such as engineered hairpin sgRNAs and chemical modifications of sgRNAs [227] , [228] .
As we know, the interaction between Cas9 and DNA affects the stability of DNA-Cas9/sgRNA complex as well as tolerance to mismatch [229] . Therefore, high-fidelity SpCas9 variants have been developed by introducing amino substitution(s) into Cas9 protein in order to destabilize the function structure of the CRISPR complex [230] . Researchers have developed several highly effective Cas9 mutants, high-fidelity Cas9 (SpCas9-HF1), enhanced specificity Cas9 (eSpCas9), hyper-accurate Cas9 (HypaCas9), etc [231] , [232] , [233] . All of them can significantly reduce off-target effects while retain robust target cleavage activity.
Recently, a double-nicking strategy has been developed to minimize off-target effects, which employs two catalytic mutant Cas9-D10A nickases and a pair of sgRNAs to produce a cleavage on each strand of the target DNA, thus forming a functional double strand break [234] . Additionally, it was proven that the fusion protein generated by combining dCas9 with Fok Ⅰ nuclease can also reduce off-target effects [235] . Only when the two fusion protein monomers are close to each other to form dimers, can they perform the cleavage function [235] . This strategy could greatly reduce DNA cleavage at non-target sites.
“Off switches” for CRISPR-Cas9 system was first discovered by Pawluk et al. in 2016. They identified three naturally existing protein families, named as “anti-CRISPRs”, which can specifically inhibit the CRISPR-Cas9 system of Neisseria meningitidis [236] . Later, Rauch et al. discovered four unique type IIA CRISPR-Cas9 inhibitor proteins encoded by Listeria monocytogenes prophages, and two of them (AcrllA2 and AcrllA4) can block SpCas9 when assayed in Escherichia coli and human cells [237] . Recently, Doudna et al. discovered two broad-spectrum inhibitors of CRISPR-Cas9 system (AcrllC1 and AcrllC3) [238] . Therefore, in order to reduce off-target effects, the “anti-CRISPRs” could be used to prevent the continuous expression of Cas9 protein in cells to be edited.
The concentration of Cas9/sgRNA can also affect the frequency of off-target mutations [239] . Thus, the optimal concentration of Cas9 and sgRNA needs to be determined by pre-experiment. Besides, the formulation of CRISPR-Cas9 can affect the frequency of off-target mutations as well. Cas9 nucleases can be delivered into target cells in 3 different forms: DNA expression plasmid, mRNA or recombination protein [240] . Currently, the use of Cas9/sgRNA ribonucleoprotein complexes (Cas9-RNPs), which are composed of purified Cas9 proteins in combination with sgRNA, is becoming more and more widespread. It was found that delivery as plasmid usually produces more off-targets than delivery as RNPs, since the CRISPR-Cas system is active for a shorter time without Cas9 transcription and translation stages [241] , [242] .
Nowadays, how to effectively deliver CRISPR-Cas components to specific cells, tissues and organs for precisely directed genome editing is still a major problem in gene therapy. Ideal delivery vectors should have the advantages of non-toxicity, well targeting property, high efficiency, low cost, and biodegradability [35] , [156] . At present, three main delivery methods have been employed in delivering CRISPR-Cas components, including physical, viral and non-viral methods [243] . Physical methods are the simplest way to deliver CRISPR-Cas components, including electroporation, microinjection and mechanical cell deformation. They are simple and efficient, which can also improve the expression of genes, and being widely applied in in vitro experiments [243] , [244] . In addition, viral vectors, such as adenovirus, adeno-associated virus (AAV) and lentivirus viral vectors, are being widely used for both in vitro / ex vivo and in vivo delivery due to their high delivery efficiency. They are commonly used for gene delivery in gene therapy, and some of them have been approved for clinical use [245] , [246] . However, safety issue of viral vectors is still a major problem needed to be solved in pre-clinical trials. Therefore, researchers have turned their attention to non-viral vectors, for instance, liposomes, polymers and nanoparticles [247] . Based on the advantages of safety, availability and cost-effectiveness, they are becoming a hotspot for the delivery of CRISPR-Cas components [248] .
Since all these delivery methods have both advantages and disadvantages, it’s necessary to design a complex of viral vectors and non-viral vectors, which combines the advantages of both vectors. Along with the deepening of research, various carriers could be modified by different methods to increase the delivery efficiency and reduce the toxicity [249] . In addition, more novel vectors, such as graphene and carbon nanomaterials (CNMs), could also be applied in the delivery of CRISPR-Cas components [250] , [251] .
Since the components of CRISPR-Cas systems are derived from bacteria, host immune response to Cas gene and Cas protein is regarded as one of the most important challenges in the clinical trials of CRISPR-Cas system [156] , [252] . It was found that in vivo delivery of CRISPR-Cas components can elicit immune responses against the Cas protein [252] , [253] . Furthermore, researchers also found that there were anti-Cas9 antibodies and anti-Cas9 T cells existing in healthy humans, suggesting the pre-existing of humoral and celluar immune responses to Cas9 protein in humans [254] . Therefore, how to detect and reduce the immunogenicity of Cas proteins is a major challenge will be faced in clinical application of CRISPR-Cas systems. Researchers are trying to handle this problem by modifying Cas9 protein or using Cas9 homologues [255] .
Recently, two independent research groups found that CRISPR-Cas mediated double-stranded breaks (DSBs) can activate the p53 signaling pathway [256] , [257] . This means that genetically edited cells are likely to become potential cancer initiating cells, and clinical treatment with CRISPR-Cas systems might inadvertently increase the risk of cancer [256] , [257] , [258] . Although there is still no direct evidence to confirm the relationship between CRISPR-Cas mediated genome editing and carcinogenesis, these studies once again give a warning on the application of CRISPR-Cas systems in gene therapy. It reminds us that there is still a long way to go before CRISPR-Cas systems could be successfully applied to humans.
CRISPR-Cas mediated genome editing has attracted much attention since its advent in 2012. In theory, each gene can be edited by CRISPR-Cas systems, even genes in human germ cells [259] . However, germline gene editing is forbidden in many countries including China, for it could have unintended consequences and bring ethical and safety concerns [260] .
However, in March 2015, a Chinese scientist, Junjiu Huang, published a paper about gene editing in human tripronuclear zygotes in the journal Protein & Cell, which brings the ethical controversy of human embryo gene editing to a climax [261] . Since then, genome editing has been challenged by ethics and morality, and legal regulation of genome editing has triggered a heated discussion all around the world.
Then, on Nov. 28, 2018, the day before the opening of the second international human genome editing summit, Jiankui He, a Chinese scientist from the Southern University of Science and Technology, announced that a pair of gene-edited babies, named Lulu and Nana, were born healthy in China this month. They are the world’s first gene-edited babies, whose CCR5 gene has been modified, making them naturally resistant to HIV infection after birth [262] . The announcement has provoked shock, even outrage among scientists around the world, causing widespread controversy in the application of genome editing.
The society was shocked by this breaking news, for it involves genome editing in human embryos and propagating into future generations, triggering a chorus of criticism from the scientific community and bringing concerns about ethics and security in the use of genome editing. Therefore, scientists call on Chinese government to investigate the matter fully and establish strict regulations on human genome editing. Global supervisory system is also needed to ensure genome editing of human embryos moving ahead safely and ethically [263] .
Since CRISPR-Cas mediated genome editing technologies have provided an accessible and adaptable means to alter, regulate, and visualize genomes, they are thought to be a major milestone for molecular biology in the 21st century. So far, CRISPR-Cas systems have been broadly applied in gene function analysis, human gene therapy, targeted drug development, animal model construction and livestock breeding, which fully prove their great potential for further development. However, there are still some limitations to overcome in the practical applications of CRISPR-Cas systems, and great efforts still need to be made to evaluate their long-term safety and effectiveness.
Yuanyuan Xu: Conceptualization, Writing - original draft. Zhanjun Li: Supervision, Validation, Writing - review & editing.
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
This study was financially supported by the National Key Research and Development Program of China Stem Cell and Translational Research (2017YFA0105101). The Program for Changjiang Scholars and Innovative Research Team in University (No.IRT_16R32). The Strategic Priority Research Program of the Chinese Academy of Sciences (XDA16030501, XDA16030503), Key Research & Development Program of Guangzhou Regenerative Medicine and Health Guangdong Laboratory(2018GZR110104004).
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CRISPR-Cas9 genome editing exploits the CRISPR-Cas system to modify a genome in a targeted manner. Guided by RNA, the Cas9 endonuclease breaks DNA at a target sequence. Imprecise repair of the double strand break can result in insertion or deletion mutations, while repair pathways can be engineered to introduce specific point mutations or insertions.
Base editing can correct the hearing-loss phenotype in mice harbouring a common mutation in the otoferlin gene.
Adeno-associated vectors (AAVs) are frequently used for the delivery of genetic cargo but their small packaging capacity is not suitable for delivery of large constructs, including most CRISPR/dCas9-effector systems. Here the authors report a compact dCas9-based repressor system packaged within a single, optimized AAV vector.
Type I CRISPR-Cas systems are widely distributed in prokaryotes but have long been overlooked for applications in eukaryotes. Here, authors develop transcriptional activators and base editors with wide editing windows (~30 nt) in human cells using compact type I-F2 Cascades
An efficient cytosine base editor was developed in cyanobacteria, which allows rapid and precise C → T point mutation and gene inactivation. This genome editing tool will accelerate the metabolic engineering and fundamental researches in cyanobacteria.
Population-scale genome modification can alter the composition or fate of wild populations. Here the authors introduce Allele Sails as a method for spreading genetic changes throughout a population.
The hearing-loss phenotype can be corrected via the injection, into the inner ear, of a base editor packaged in an adeno-associated virus, as shown in mice harbouring a mutation homozygous to human OTOF and in humanized mice with the human mutation.
Homing-based gene drives show promise for malaria control through reducing or modifying mosquito populations, but understanding gene drive mechanisms is vital for policy. Here, authors show minimal carryover of extra sequences with gene drives, and potential for mixed methods of gene drive inheritance.
Epigenetic editing with charm.
A dual hearing system helps fish pinpoint a sound’s source — plus uncovering the secrets of the sensory structures that respond to touch during sex.
It’s not just people with ultra-rare disorders who could benefit from hyper-personalized therapies. Scientists and regulators must work together to ensure the benefits are spread.
Researchers in India fought to develop what could have been the first therapy to use gene-editing to halt a rare neurodegenerative disease. The efforts hold lessons for the messy state of modern drug development.
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Previous research on CRISPR/Cas9 has focused on prokaryotic cells, and CRISPR technology started to be used in medicine, agriculture, and other fields in a paper published by Zhang Feng et al. in ...
The mechanism of CRISPR/Cas-9 genome editing can be generally divided into three steps: recognition, cleavage, and repair. 13 The designed sgRNA directs Cas-9 and recognizes the target sequence in the gene of interest through its 5ʹcrRNA complementary base pair component. The Cas-9 protein remains inactive in the absence of sgRNA.
Abstract. Recent advances in genome engineering technologies based on the CRISPR-associated RNA-guided endonuclease Cas9 are enabling the systematic interrogation of mammalian genome function. Analogous to the search function in modern word processors, Cas9 can be guided to specific locations within complex genomes by a short RNA search string.
1. Introduction. The very beginning of this exciting Clustered Regularly Interspaced Palindromic Repeats (CRISPR) story dates back to the observations published by a Japanese research group in 1987 [].However, Ishino and his colleagues could not explain much about the biological significance of their identified sequences that contained five homologous sequences of 29 nucleotides separated by ...
Metrics. CRISPR is becoming an indispensable tool in biological research. Once known as the bacterial immune system against invading viruses, the programmable capacity of the Cas9 enzyme is now ...
The historical foundation of CRISPR-Cas9 research can be traced to its identification as an adaptive immune defense mechanism in bacterial cells, serving as a robust defense against foreign DNA. Scientists have adeptly utilized CRISPR-Cas9 for precise genome editing across diverse organisms, resulting in substantial advancements and a refined ...
The CRISPR system has been classified into two major classes. In the Class 1 system, the RNA-guided target cleavage needs several effector proteins, but the Class 2 system requires only one RNA-guided endonuclease to cleave the DNA sequences [12, 20].The class 1 system of CRISPR is divided into three types I, III, and IV, and the Class 2 system is divided into types II, V, and VI [21, 22].
A HISTORY OF THE DISCOVERY OF THE MAIN COMPONENTS OF THE CRISPR-Cas9 SYSTEM. CRISPR - clustered regularly interspaced short palindromic repeats - were first discovered in the sequences of DNA from Escherichia coli bacteria and described in 1987 by Ishino et al. [] from Osaka University (Japan).At that time sequencing of these difficult-to-study DNA fragments took several months, but ...
Cas9 can be targeted to specific genomic loci via a 20-nt guide sequence on the sgRNA. The only requirement for the selection of Cas9 target sites is the presence of a PAM sequence directly 3 ...
The advent of facile genome engineering using the bacterial RNA-guided CRISPR-Cas9 system in animals and plants is transforming biology. We review the history of CRISPR (clustered regularly interspaced palindromic repeat) biology from its initial discovery through the elucidation of the CRISPR-Cas9 enzyme mechanism, which has set the stage for remarkable developments using this technology to ...
CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 is a unique genome editing tool that can be easily used in a wide range of applications, including functional genomics, transcriptomics, epigenetics, biotechnology, plant engineering, livestock breeding, gene therapy, diagnostics, and so on. This review is focused on the current CRISPR/Cas9 landscape, e.g., on Cas9 ...
One approach that might overcome many of these limitations employs extracellular vesicles as intercellular delivery devices. In this review, we first introduce the CRISPR/Cas9 system and its latest advancements, outline major applications, and summarize the current state of the art technology using exosomes or microvesicles for transporting ...
A decade of CRISPR. In the decade since the publication of CRISPR-Cas9 as a genome-editing technology, the CRISPR toolbox and its applications have profoundly changed basic and applied biological research. Wang and Doudna now review the origins and utility of CRISPR-based genome editing, the successes and current limitations of the technology ...
CRISPR-Cas9 Gene Editing for SCD and TDT. 3m 25s. Transfusion-dependent β-thalassemia (TDT) and sickle cell disease (SCD) are the most common monogenic diseases worldwide, with an annual ...
CRISPR/Cas9 has become a powerful method for making changes to the genome of many organisms. First discovered in bacteria as part of an adaptive immune system, CRISPR/Cas9 and modified versions have found a widespread use to engineer genomes and to activate or to repress the expression of genes. ... CRISPR/Cas9 for cancer research and therapy ...
The dual-tracrRNA:crRNA, when engineered as a single RNA chimera, also directs sequence-specific Cas9 dsDNA cleavage. Our study reveals a family of endonucleases that use dual-RNAs for site-specific DNA cleavage and highlights the potential to exploit the system for RNA-programmable genome editing.
As such, CRISPR/Cas9 promises to accelerate cancer research by providing an efficient technology to dissect mechanisms of tumorigenesis, identify targets for drug development, and possibly arm cells for cell-based therapies. Here, we review current applications of the CRISPR/Cas9 technology for cancer research and therapy.
This paper describes the development of a 'PAMless' CRISPR-Cas9 variant, SpRY, that dramatically broadens the number of possible genomic targets for nuclease- or non-nuclease-mediated editing.
Hepatitis B virus (HBV) infection remains a significant global health challenge, with chronic HBV leading to severe liver diseases, including cirrhosis and hepatocellular carcinoma. Current treatments often fail to eradicate the virus, highlighting the need for innovative therapeutic strategies. The CRISPR/Cas9 system has emerged as a dynamic tool for precise genome editing and presents a ...
CRISPR/Cas9 is a simple two-component system used for effective targeted gene editing. The first component is the single-effector Cas9 protein, which contains the endonuclease domains RuvC and HNH. RuvC cleaves the DNA strand non-complementary to the spacer sequence and HNH cleaves the complementary strand.
This review paper discusses these challenges, provides possible solutions, and recommends future research on the integration of CRISPR/Cas9 into sustainable aquaculture practices, focusing on the responsible management of genetically modified fish to enable the creation of growth and disease-resistant strains.
The CRISPR nuclease Cas9 is targeted by a short guide RNA that recognizes the target DNA via Watson-Crick base pairing (Figure 2C). The guide sequence within these CRISPR RNAs typically corresponds to phage sequences, constituting the natural mechanism for CRISPR antiviral defense, but can be easily replaced by a sequence of interest to ...
That year, Emmanuelle Charpentier and Jennifer Doudna published their landmark paper describing the CRISPR-Cas9 system ( Science, 17 Aug 2012). Reflecting the magnitude of their impact, these ...
Early success in treating hereditary hematological disorders opens the door to new options for treating other genetic disorders and constitutes a significant step forward in the development of gene therapy. According to current research, CRISPR/Cas9-mediated genome editing has shown enormous potential in the correction of genetic defects in autologous hematopoietic stem/progenitor cells (HSPCs ...
Clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 is a gene-editing technology causing a major upheaval in biomedical research. It makes it possible to correct errors in the genome and turn on or off genes in cells and organisms quickly, cheaply and with relative ease. It has a number of laboratory applications including rapid ...
CRISPR-Cas9 system has been used to treat SCD by repairing the β-globin gene mutation ... two independent research groups found that CRISPR-Cas mediated double-stranded breaks (DSBs) can activate the p53 ... published a paper about gene editing in human tripronuclear zygotes in the journal Protein & Cell, which brings the ethical ...
Despite significant progress in CRISPR-Cas9-mediated genome editing, the application of this technology in buffalo breeding is still in its infancy. Limited studies have investigated the comparative effectiveness of different transfection approaches for editing the MSTN gene in buffalo somatic cells and zygotes, and their impact on pregnancy ...
CRISPR-Cas9 genome editing exploits the CRISPR-Cas system to modify a genome in a targeted manner. Guided by RNA, the Cas9 endonuclease breaks DNA at a target sequence. ... Research Open Access 23 ...