REVIEW | doi:10.20944/preprints202107.0030.v1
Subject: Life Sciences, Biochemistry Keywords: Crop, CRISPR/Cas9; Resistance; RNA interference; Stress
Online: 1 July 2021 (14:13:20 CEST)
With the rapid population growth, there is an urgent need for innovative crop improvement approaches to meet the increasing demand for food. Classical crop improvement approaches involve, however, a backbreaking process that cannot equipoise with increasing crop demand. RNA based approaches i.e. RNAi-mediated gene regulation and site-specific nuclease based CRISPR/Cas9 system for gene editing has made advances in the efficient targeted modification in many crops for the higher yield and resistance to diseases and different stresses. In functional genomics, RNA interference (RNAi) is a propitious gene regulatory approach that plays a significant role in crop improvement by permitting down-regulation of gene expression by small molecules of interfering RNA without affecting the expression of other genes. Gene editing technologies viz. clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (CRISPR/Cas) have appeared prominently as a powerful tool for precise targeted modification of nearly all crops genome sequence to generate variation and accelerate breeding efforts. In this regard, the review highlights the diverse roles and applications of RNAi and CRISPR/Cas9 system as powerful technologies to improve agronomically important plants to enhance crop yields and increase tolerance to environmental stress (biotic or abiotic). Ultimately, these technologies can prove to be important in view of global food security and sustainable agriculture.
ARTICLE | doi:10.20944/preprints202105.0422.v1
Subject: Medicine & Pharmacology, Allergology Keywords: genome editing; CRISPR; Cas9; in vivo editing
Online: 18 May 2021 (11:27:46 CEST)
The development of CRISPR associated proteins, such as Cas9, has led to increased accessibility and ease of use in genome editing. However, additional tools are needed to quantify and identify successful genome editing events in living animals. We developed a method to rapidly and quantitatively monitor gene editing activity non-invasively in living animals that also facilitates confocal microscopy and nucleotide level analyses at the end of study. Here we report a new CRISPR “footprinting” approach to activate luciferase and fluorescent proteins in mice as a function of gene editing. This system is based on experience with our prior Cre-detector system and is designed for Cas editors able to target LoxP including gRNAs including SaCas9 and ErCas12a [1, 2]. These CRISPRs cut specifically within LoxP, an approach that is a departure from previous gene editing in vivo activity detection techniques that targeted adjacent stop sequences. In this sensor paradigm, CRISPR activity was monitored non-invasively in living Cre reporter mice (FVB.129S6(B6)-Gt(ROSA)26Sortm1(Luc)Kael/J and Gt(ROSA)26Sortm4(ACTB-tdTomato,-EGFP)Luo/J, which will be referred to as LSL and mT/mG throughout the paper) after intramuscular or intravenous hydrodynamic plasmid injections, demonstrating utility in two diverse organ systems. The same genome-editing event was examined at the cellular level in specific tissues by confocal microscopy to determine the identity and frequency of successfully genome-edited cells. Further, SaCas9 induced targeted editing at efficiencies that were comparable to Cre recombinase demonstrating high effective delivery and activity in a whole animal. This work establishes genome editing tools and models to track CRISPR editing in vivo non-invasively and to fingerprint the identity of targeted cells. This approach also enables similar utility for any of the thousands of previously generated LoxP animal models.
REVIEW | doi:10.20944/preprints202101.0212.v1
Online: 12 January 2021 (10:14:46 CET)
The constitutively active tyrosine kinase BCR/ABL1 oncogene plays a key role in human chronic myeloid leukemia development and disease maintenance, and determines most of the features of this leukemia. For this reason, tyrosine kinase inhibitors are the first-line treatment, offering most patients a life expectancy like that of an equivalent healthy person. However, since the oncogene is not destroyed, lifelong oral medication is essential, even though this trigger adverse effects in many patients. Furthermore, leukemic stem cells remain quiescent and resistance is observed in approximately 25% of patients. Thus, new therapeutic alternatives are still needed. In this scenario, the emergence of CRISPR technology can offer a definitive treatment based on its capacity to disrupt coding sequences. This review describes CML disease and the main advances in the genome-editing field by which it may be treated in the future.
CONCEPT PAPER | doi:10.20944/preprints202003.0321.v1
Subject: Life Sciences, Biotechnology Keywords: bookmark; CRISPR/Cas9; complementation; clostridium; knock-out
Online: 23 March 2020 (00:50:23 CET)
Phenotypic complementation of gene knock-outs is an essential step in establishing function. Here we describe a simple strategy for ‘gold standard’ complementation in which the mutant allele is replaced in situ with a wild type (WT) allele in a procedure that exploits CRISPR/Cas9. The method relies on the prior incorporation of a unique 24 nucleotide (nt) ‘bookmark’ sequence into the mutant allele to act as a guide RNA target during its Cas9-mediated replacement with the WT allele. The bookmark comprises a 23 nt Cas9 target sequence plus an additional nt to ensure the deletion is in-frame. Here, bookmarks are tailored to Streptococcus pyogenes CRISPR/Cas9, but could be designed for any CRISPR/Cas system. For proof of concept, 9 bookmarks were tested in Clostridium autoethanogenum. Complementation efficiencies reached 91%. As complemented strains are indistinguishable from their progenitors, concerns over contamination may be satisfied by incorporation of ‘watermark’ sequences into the complementing genes.
REVIEW | doi:10.20944/preprints202001.0191.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: hybrid vigor; flowering plants; apomixis; CRISPR/Cas9
Online: 17 January 2020 (10:30:45 CET)
The hybrid seeds of several important crops with supreme qualities, including yield, biotic and abiotic stress tolerance, have been cultivated from decades. Thus far, a major challenge with hybrid seed, it does not hold ability to produce plants with same qualities over subsequent generations. Apomixis exist naturally an asexual mode of reproduction in flowering plants via avoiding meiosis and ultimately leads to seed production. Apomixis possess potential to preserve hybrid vigor for multiple generations for economically important plant genotypes. The evolution and genetics of asexual seed production is unclear and need much more efforts to find its genetic architecture. To fix hybrid vigor synthetic apomixis has been suggested an alternative. The development of MiMe (Mitosis instead of Meiosis) genotypes are utilized further for clonal gametes production. However, the identification and parental origin of genes responsible for synthetic apomixis are less known and need further understanding. Genome modifications utilizing genome editing technologies (GETs) like clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (cas9) a reverse genetics tool has paved way to utilize emerging technologies in plant molecular biology. From the last decade, several genes in important crops have been successfully edited. The vast availability of GETs has made the functional genomics studies easy to conduct in crops important for food security. The disruption of expression of genes specific to egg cell MATRILINEAL (MTL) or BABY BOOM1 (BBM1) through CRISPR/Cas genome editing system can promote haploid plants. The establishment of synthetic apomixis by engineering MiMe genotype by genome editing BBM1 expression or disruption of MTL leads toward clonal seed production. In present review, we discussed the current development in plants by utilizing CRISPR/Cas9 technology and its possibility of promoting apomixis in crops to preserve hybrid vigour. In addition to this, genetics, evolution, epigenetic modifications and strategy for MiMe genotype development has been discussed in detail.
ARTICLE | doi:10.20944/preprints202211.0173.v1
Subject: Biology, Plant Sciences Keywords: aconitate hydratase; CRISPR/Cas9; male sterility; seedless tomato
Online: 9 November 2022 (10:01:29 CET)
Tomato (Solanum lycopersicum) is one of the most cultivated vegetables in the world due to its consumption in a large variety of raw, cooked, or processed foods. Tomato breeding and productivity highly depend on the use of hybrid seeds and their higher yield, environmental adaption, and disease tolerance. However, the emasculation procedure during hybridization raises tomato seed production costs and labor expenses. Using male sterility is an effective way to reduce the cost of hybrid seeds and ensure cultivar purity. Recent developments in CRISPR genome editing technology enabled tomato breeders to investigate the male sterility genes and to develop male-sterile tomato lines. In the current study, the tomato Acotinase (SlACO) gene family was investigated via in-silico tools and functionally characterized with CRISPR/Cas9-mediated gene disruption. Genome-wide blast and HMM search represented two SlACO genes located on different tomato chromosomes. Both genes were estimated to have a segmental duplication in the tomato genome due to their identical motif and domain structure. One of these genes, SlACO2, showed a high expression profile in all generative cells of tomato. Therefore, the SlACO2 gene was targeted with two different gRNA/Cas9 construct to identify their functional role in tomato. The gene was mutated in a total of 6 genome-edited tomato lines, 2 of which were homozygous. Surprisingly, pollen viability was found to be extremely low in mutant plants compared to their wild-type (WT) counterparts. Likewise, the number of seeds per fruit also sharply decreased more than fivefold in mutant lines (10-12 seed) compared to that in WT (67 seed). The pollen shape, anther structures, and flower colors/shapes were not significantly varied between the mutant and WT tomatoes. The mutated lines were also subjected to salt and mannitol-mediated drought stress to test the effect of SlACO2 on abiotic stress tolerance. The results of the study indicated that mutant tomatoes have higher tolerance with significantly lower MDA content under stress conditions. This is the first CRISPR-mediated characterization of ACO genes on pollen viability, seed formation, and abiotic stress tolerance in tomato.
ARTICLE | doi:10.20944/preprints202109.0250.v1
Online: 15 September 2021 (09:16:39 CEST)
Folic acid, one of the 13 essential vitamins, plays an important role in cardiovascular development. Mutations in folic acid synthesis gene 5,10-methylenetetrahydrofolate reductase (MTHFR) is significantly associated with the occurrence of congenital heart disease. However, the mechanisms underlying the regulation of cardiac development by mthfr gene are poorly understood. Here, we exposed zebrafish embryos to excessive folate or folate metabolism inhibitors. And we established a knock-out mutant of mthfr gene in zebrafish by using CRISPR/Cas9. The zebrafish embryos of insufficient or excessive folic acid, and mthfr-/- mutant all gave rise to early pericardial edema and cardiac defect at 3 days after fertilization(dpf). Furthermore, the folic acid treated embryos showed abnormal movement at 5dpf. The expression levels of cardiac marker genes hand2, gata4 and nppa changed in the abnormality of folate metabolism embryos and mthfr-/- mutant, and there is evidence that they are related to the change of methylation level caused by the change of folate metabolism. In conclusion, our study provides a novel model for the in-depth study of MTHFR gene and folate metabolism. And our results reveal that folic acid has a dose-dependent biphasic effect on early cardiac development.
ARTICLE | doi:10.20944/preprints202003.0437.v2
Subject: Life Sciences, Biochemistry Keywords: antivirals; broad-spectrum; CRISPR; Cas9; SARS; COVID-19
Online: 8 January 2021 (13:53:55 CET)
All RNA viruses deliver their genomes into target host cells through processes distinct from normal trafficking of cellular RNA transcripts. The delivery of viral RNA into most cells hence triggers innate antiviral defenses that recognize viral RNA as foreign. In turn, viruses have evolved mechanisms to subvert these defenses, allowing them to thrive in target cells. Therefore, drugs activating defense to exogenous RNA could serve as broad-spectrum antiviral drugs. Here we show that transcriptional signatures associated with cellular responses to the delivery of a non-viral exogenous RNA sequence into human cells predict small molecules with broad-spectrum antiviral activity. In particular, transcriptional responses to the delivery of Cas9 mRNA into human hematopoietic stem and progenitor cells (HSPCs) highly matches those triggered by small molecules with broad-spectrum antiviral activity such as emetine, homoharringtonine, pyrvinium pamoate and anisomycin, indicating that these drugs are potentially active against other RNA viruses. Furthermore, these drugs have been approved for other indications and could thereby be repurposed to novel viruses. We propose that the antiviral activity of these drugs to SARS-CoV-2 should therefore be determined as they have been shown as active against other coronaviruses including SARS-CoV-1 and MERS-CoV. Indeed, two of these drugs- emetine and homoharringtonine- were independently shown to inhibit SARS-CoV-2 as this article was in preparation. These drugs could also be explored as potential adjuvants to COVID-19 vaccines in development due to their potential effect on the innate antiviral defenses that could bolster adaptive immunity when delivered alongside vaccine antigens.
COMMUNICATION | doi:10.20944/preprints202005.0253.v1
Subject: Life Sciences, Genetics Keywords: Cas9; Cas12a; Cpf1; zebrafish; gene knockout; repair outcome
Online: 15 May 2020 (10:16:55 CEST)
CRISPR/Cas genome editing is a widely used research technology. Its simplest variant is gene knockout resulting from reparation errors after introduction of dsDNA breaks by Cas nuclease. We compared the outcomes of the break repair by two commonly used nucleases (SpCas9 and LbCas12a) in zebrafish embryos to reveal if application of one nuclease is advantageous in comparison to the other. To address this question, we injected ribonucleoprotein complexes of nucleases and corresponding guide RNAs in zebrafish zygotes and three days later sequenced the target gene regions. We found that LbCas12a breaks resulted in longer deletions and more rare inserts, in comparison to those generated by SpCas9, while the editing efficiencies of both nucleases were the same. On the other hand, overlapping protospacers were shown to lead to similarities in repair outcome, although they were cut by two different nucleases. Thus, our results indicate that the repair outcome depends both on the nuclease mode of action and on protospacer sequence.
ARTICLE | doi:10.20944/preprints201904.0031.v1
Subject: Life Sciences, Biochemistry Keywords: Rett syndrome; MeCP2; CRISPR/cas9; transcriptome; calcium ion
Online: 2 April 2019 (12:28:17 CEST)
Objective: Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in MeCP2, a transcription factor. MeCP2 mutations cause abnormal expression of downstream genes and eventually lead to brain dysfunction. The role of MeCP2 in brain neural development remains unclear. To further elucidate this role, a MeCP2-null rat model was created with the CRISPR/cas9 system. Method: A MeCP2-cas9 vector was constructed and then microinjected into fertilized rat ova in vitro. Two mutations by CRISPR/cas9 were confirmed to cause deletions in exon 2 of MeCP2 via DNA sequencing, and protein expression was measured by Western blotting. Transcriptome data for three brain tissues, the cerebellum, cerebral cortex and hippocampus, were obtained via next-generation sequencing. Results: MeCP2-null rats were successfully obtained, and preliminary analysis showed that the MeCP2-null rats exhibited motor dysfunction and anxious and depressed behaviour. In addition, differentially expressed genes (DEGs) were identified in the three MeCP2-null brain tissues compared to wild-type rat brain tissues. In the rat cerebellum, 388 downregulated DEGs were mainly involved in the calcium ion signalling pathway and the PI3K-Akt signalling pathway. In the cerebral cortex, 386 upregulated DEGs were primarily involved in intracellular signal transduction, protein phosphorylation and the MAPK signalling pathway. In the hippocampus, the DEGs were related to the MAPK signalling pathway. Conclusion: We constructed a MeCP2-null rat model with unique features with CRISPR/cas9 technology to study RTT and analysed DEGs in three rat brain tissues to highlight potential targets for the development of new medicines.
REVIEW | doi:10.20944/preprints202108.0387.v1
Online: 18 August 2021 (14:21:46 CEST)
Novel Cellular Immunotherapy with engineered T cells has improved cancer treatment and established therapeutic promises to prevent tumor formation in clinical studies. Due to certain restrictions and difficulties, CAR and TCR T cells therapies were inadequate at points. CRISPR Cas9 genome-editing tool has a significant potential for these two cell-based therapies. As a specialized gene-editing technique, CRISPR Cas9 is used to repair genetic alternation with minimum damage. It is used as an adjunct to Immunotherapy to stimulate a more robust immune response. CRISPR has long outpaced other target-specific genome editing methods such as ZFNs and TALEN due to its high efficiency, competence in targeting, and stable operating condition. CRISPR can overcome the two major drawbacks of universal CAR T cells: allorejection and graft-vs-host disease. TCR-based T cell treatment can reduce inappropriate binding between endogenous and transgenic TCR, resulting in a reduction of severe toxicity. The CAR and TCR T based cell therapies uphold an excellent future for tumor malignancies This article has elucidated the administration of CRISPR Cas9 in Novel Cellular Immunotherapy, CAR, and TCR T cell therapy. However, this article did not fail to observe this technology's ethical concerns, limitations, and challenges. Furthermore, the article compares CRISPR-mediated allogeneic CAR T cell to TCR-T cell therapy.
ARTICLE | doi:10.20944/preprints202106.0357.v1
Subject: Life Sciences, Biochemistry Keywords: CYP1B1; craniofacial development; CRISPR/Cas9; Congenital glaucoma; knockout zebrafish.
Online: 14 June 2021 (11:53:54 CEST)
CYP1B1 loss-of-function (LoF) is the main known genetic alteration present in recessive primary congenital glaucoma (PCG), an infrequent disease characterized by delayed embryonic development of the ocular iridocorneal angle and caused by poorly understood molecular mechanisms. To model CYP1B1 LoF underlying PCG, we developed a cyp1b1 knockout (KO) zebrafish line using CRISPR/Cas9 genome editing. This line carries the c.535_667del frameshift mutation that results in a 72% mRNA reduction with residual mRNA predicted to produce an inactive truncated protein (p.(His179Glyfs*6)). Craniofacial defects and jaw maldevelopment were observed in 23% of somatic mosaic F0 crispant larvae (144 hpf). These early phenotypes were not detected in KO F3 larvae (144 hpf) but 27% of adult fishes (4 months) showed uni or bilateral craniofacial alterations, indicating the existence of incomplete penetrance and variable expressivity. These phenotypes increased to 86% in the adult offspring of inbred progenitors with craniofacial defects. No glaucoma-related phenotypes were observed in the cyp1b1 mutants. Transcriptomic analyses of the offspring (7dpf) of KO cyp1b1 progenitors with adult-onset craniofacial defects revealed that differentially expressed genes were functionally enriched in groups related with extracellular matrix and cell adhesion, cell growth and proliferation, lipid metabolism (retinoids, steroids, and fatty acids, and oxidation-reduction processes which included several cytochrome P450 genes) and inflammation. In summary, this study shows the complexity of phenotypes and molecular pathways associated with cyp1b1 LoF, with species-dependency, and provides evidence for dysregulation of extracellular matrix gene expression as one of the mechanisms underlaying pathogenicity associated with cyp1b1 disruption.
REVIEW | doi:10.20944/preprints202011.0264.v1
Subject: Biology, Anatomy & Morphology Keywords: Bioethanol; Kluyveromyces marxianus; Omics technologies; gTME, and CRISPR-Cas9
Online: 9 November 2020 (08:38:20 CET)
Bioethanol has been considered as an excellent alternative to fossil fuels since it importantly contributes to the reduced consumption of the crude oil and to the alleviation of environmental pollution . Up to now, the baker yeast Saccharomyces cerevisiae is the most common eukaryotic microorganism used in ethanol production. The inability of S. cerevisiae to grow on pentoses, however, hinders its effective growth on plant biomass hydrolysates, which contain large amounts of C5 and C12 sugars. The industrial-scale bioprocessing requires high temperature bioreactors, diverse carbon sources, and the high titer production of volatile compounds . These criteria indicate that the search for alternative microbes possessing useful traits that meet the required standards of bioethanol production is necessary. Compared to other yeasts, Kluyveromyces marxianus has several advantages over the others, e.g. it could grow on a broad spectrum of substrates (C5, C6 and C12 sugars) , tolerate to high temperature, toxin [4,5] and a wide range of pH values , and produce volatile short-chain ester . K. marxianus also shows a high ethanol production rate at high temperature and is a Crabtree-negative species . These attributes make K. marxianus a promise as an industrial host for the biosynthesis of biofuels and other valuable chemicals.
Subject: Life Sciences, Molecular Biology Keywords: BE4; CRISPR-Cas9; Tyr; cytosine base editing; mouse model
Online: 30 December 2019 (11:16:30 CET)
Most human genetic disease arises from point mutations. These genetic diseases can theoretically be corrected by gene therapy but clinic practice is still far from mature. Nearly half of the pathogenic single-nucleotide polymorphisms (SNPs) are caused by G:C>A:T or T:A>C:G base changes. The best current methods to repair these changes are by base editing without footprint using recently developed CRISPR-Cas9 technology by David Liu’s lab. These base editing methods have been confirmed with precision and efficiency in cultured mammalian cells, but it is barely confirmed and the efficiency is still very low. Animal models are important in dissecting pathogenic mechanism for human genetic diseases and efficacy testing of base correction in vivo. Cytidine base editor BE4 is a newly developed version of cytidine base editing system that converts cytidine (C) to uridine (U) in cultured mammalian cells but has not been proven in vivo. In this study, we have tested this system in cells to inactivate GFP gene and in mice by introducing single-base substitution that leads to a stop codon in tyrosinase gene. High percentage albino coat-colored mice were obtained from black coat-colored donor zygotes after pronuclei microinjection. Sequencing results showed that expected base changes were obtained with high precision and efficiency (56.25%). There are no off-targeting events identified in predicted off-target sites. Results confirm BE4 system can work in vivo with high precision and efficacy, and has great potentials in clinic to repair human genetic mutations.
ARTICLE | doi:10.20944/preprints202201.0211.v1
Subject: Biology, Plant Sciences Keywords: microalgae; CRISPR/Cas9; gene editing; spermidine; SPD1; auxotrophy; selectable marker
Online: 14 January 2022 (11:55:22 CET)
Biotechnological application of the green microalga Chlamydomonas reinhardtii hinges on the availability of selectable markers for effective expression of multiple transgenes. However, biological safety concerns limit the establishment of new antibiotic resistance genes and until today, only few auxotrophic markers exist for C. reinhardtii. The recent improvements in gene editing via CRISPR/Cas9 allows directed exploration of new endogenous selectable markers. Since editing frequencies with CRISPR/Cas9 techniques are often low, the Cas9-sgRNA ribonucleoprotein (RNP) delivery protocol was strategically optimized by applying nitrogen starvation to the pre-culture, increasing editing frequencies from 10% to 66% after pre-selection. Probing the essential polyamine biosynthesis pathway, the spermidine synthase gene (SPD1) is shown to be a potent selectable marker with versatile biotechnological applicability. Very low levels of spermidine (0.75 mg/L) were required to maintain normal mixotrophic and phototrophic growth in newly designed spermidine auxotrophic strains. Complementation of these strains with a synthetic SPD1 gene was achieved when the mature protein was targeted to either the cytosol or the chloroplast. This work highlights the potential of new selectable markers for biotechnology as well as basic research and proposes an effective pipeline for the identification of new auxotrophies in C. reinhardtii.
Subject: Medicine & Pharmacology, Gastroenterology Keywords: CRISPR/Cas9; celiac disease; wheat; sgRNA; gluten; low-immunogenic wheat
Online: 29 September 2021 (15:39:12 CEST)
Wheat gluten contains epitopes that trigger celiac disease (CD). A life-long strict gluten-free diet is the only treatment accepted for CD. However, very low-gluten wheat may provide an alternative treatment to CD. Conventional plant breeding methods are not sufficient to produce celiac-safe wheat. RNA interference technology, to some extent, succeeded in the development of safer wheat varieties. However, these varieties had multiple challenges in their implementation. Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease 9 (CRISPR/Cas9) is a versatile gene-editing tool that has the ability to edit the immunogenic gluten genes. So far, only a few studies have applied CRISPR/Cas9 to modify the wheat genome. In this article, we reviewed published literature that applied CRISPR/Cas9 in wheat genome editing to investigate the current status of the CRISPR/Cas9 system to produce a low-immunogenic wheat variety. We found that in recent years, the CRISPR/Cas9 system has been continuously improved to edit the complex hexaploid wheat genome. Although some reduced immunogenic wheat varieties have been reported, CRISPR/Cas9 has still not been fully explored in editing the wheat genome. We conclude that further studies are required to apply the CRISPR/Cas9 gene-editing system efficiently for the development of celiac-safe wheat variety and to establish it as a “tool to celiac safe wheat.”
Subject: Life Sciences, Biochemistry Keywords: Mollusc; selective breeding; gene editing; disease resistance; transgenesis; CRISPR/Cas9
Online: 15 October 2020 (16:06:27 CEST)
Molluscan aquaculture is a major contributor to global seafood production, but is hampered by infectious disease outbreaks which can cause serious economic losses. Selective breeding has been widely used to improve disease resistance in major agricultural and aquaculture species, and has clear potential in molluscs, albeit its commercial application remains at a formative stage. Advances in genomic technologies, especially development of cost-efficient genomic selection, have potential to accelerate genetic improvement. However, tailored approaches are required due to the distinctive reproductive and lifecycle characteristics of molluscan species. Transgenesis and genome editing, in particular CRISPR/Cas systems, have been successfully trialled in molluscs, and may further understanding and improvement of genetic resistance to disease through targeted changes to the host genome. Whole organism genome editing is achievable on a much greater scale compared to other farmed species, making genome-wide CRISPR screening approaches plausible. This review discusses the current state and future potential of selective breeding, genomic tools, and genome editing approaches to understand and improve host resistance to infectious disease in molluscs.
REVIEW | doi:10.20944/preprints202007.0578.v1
Subject: Biology, Plant Sciences Keywords: CRISPR; CAS9; CAS12a; NHEJ; Base editing; PAM; Temperature Sensitivity; Agriculture
Online: 24 July 2020 (11:43:03 CEST)
Global population is predicted to approach 10 billion by 2050, an increase of over 2 billion from today. To meet the demands of growing, geographically and socio-economically diversified nations, we need to diversity and expand agricultural production. This expansion of agricultural productivity will need to occur under increasing biotic, and environmental constraints driven by climate change. Clustered regularly interspaced short palindromic repeats-site directed nucleases (CRISPR-SDN) and similar genome editing technologies will likely be key enablers to meet future agricultural needs. While the application of CRISPR-Cas9 mediated genome editing has led the way, the use of CRISPR-Cas12a is also increasing significantly for genome engineering of plants. The popularity of the CRISPR-Cas12a, the type V (class-II) system, is gaining momentum because of its versatility and simplified features. These include the use of a small guide RNA devoid of trans-activating crispr RNA (tracrRNA), targeting of T-rich regions of the genome where Cas9 is not suitable for use, RNA processing capability facilitating simpler multiplexing, and its ability to generate double strand breaks (DSB) with staggered ends. Many monocot and dicot species have been successfully edited using this Cas12a system and further research is ongoing to improve its efficiency in plants, including improving the temperature stability of the Cas12a enzyme, identifying new variants of Cas12a or synthetically producing Cas12a with flexible PAM sequences. In this review we provide a comparative survey of CRISPR-Cas12a and Cas9, and provide a perspective on applications of CRISPR-Cas12 in agriculture.
ARTICLE | doi:10.20944/preprints202003.0424.v1
Subject: Life Sciences, Genetics Keywords: primary congenital glaucoma; exome sequencing; GUCA1C; GCAP3; zebrafish; CRISPR/Cas9
Online: 29 March 2020 (06:33:17 CEST)
Primary congenital glaucoma (PCG) is a heterogeneous, inherited, and severe optical neuropathy caused by apoptotic degeneration of the retinal ganglion cell layer. Whole-exome sequencing analysis of one PCG family identified two affected siblings who carried a low-frequency homozygous nonsense GUCA1C variant (c.52G>T/p.Glu18Ter/rs143174402). This gene encodes GCAP3, a member of the guanylate cyclase activating protein family, involved in phototransduction and with a potential role in intraocular pressure regulation. Segregation analysis supported the notion that the variant was coinherited with the disease in an autosomal recessive fashion. GCAP3 was detected immunohistochemically in the adult human ocular ciliary epithelium and retina. To evaluate the ocular effect of GUCA1C loss-of-function, a guca1c knockout zebrafish line was generated by CRISPR/Cas9 genome editing. Immunohistochemistry demonstrated the presence of GCAP3 in the non-pigmented ciliary epithelium and retina of adult wild-type fishes. Knockout animals presented up-regulation of the glial fibrillary acidic protein in Müller cells and evidence of retinal ganglion cell apoptosis, indicating the existence of gliosis and glaucoma-like retinal damage. In summary, our data provide evidence for the role of GUCA1C as a candidate gene in PCG and offer new insights into the function of this gene in the ocular anterior segment and the retina.
ARTICLE | doi:10.20944/preprints201811.0159.v1
Subject: Biology, Entomology Keywords: Bombyx mori; BmNPV; antiviral therapeutic; CRISPR/Cas9; multi-gene editing
Online: 7 November 2018 (10:23:52 CET)
Clustered regularly interspaced short palindromic repeats/associated protein 9 nuclease (CRISPR/Cas9) technology guided by a single-guide RNA (sgRNA) has recently opened a new avenue for antiviral therapy. A unique capability of the CRISPR/Cas9 system is multiple genome engineering. However, there are few applications in insect viruses by a single Cas9 enzyme targeting two or more sgRNA at different genomic sites for simultaneous production of multiple DNA breaks. To address the need for multi-gene editing and sustained delivery of multiplex CRISPR/Cas9-based genome engineering tools, we developed a one-vector (pSL1180-Cas9-U6-sgRNA) system to express multiple sgRNA and Cas9 protein to excise Bombyx mori nucleopolyhedrovirus (BmNPV) in insect cells. Here, ie-1, gp64, lef-11, and dnapol genes were screened and identified as multiple sgRNA editing sites according to the BmNPV system infection and DNA replication mechanism. Furthermore, we constructed a multiplex editing vector sgMultiple to efficiently regulate multiplex gene editing steps and inhibit BmNPV replication after viral infection. This is the first report that describes the application of multiplex CRISPR/Cas9 system inhibiting insect virus replication. This multiplex system can significant enable the potential of CRISPR/Cas9-based multiplex genome engineering in transgenic silkworms.
REVIEW | doi:10.20944/preprints202107.0182.v1
Subject: Life Sciences, Biochemistry Keywords: CRISPR-Cas9; Genome editing; plant editing; bacterial immune system; genetic disease
Online: 8 July 2021 (09:50:22 CEST)
Clustered regularly interspaced short palindromic repeats or CRISPR, one of the major technological tools from nature's toolbox, has revolutionized the scientific world with its potential use in humans and plants. CRISPR Cas9 was first known as an adaptive immune system of bacteria. It is a system that cleaves foreign DNA. It has been exploited to be used as a genome editing tool for correcting genetic diseases in humans, for plants to create stress-resistant plants, and for a variety of different purposes. This review provides a basic overview of its applications in different areas of biological research. It has immense potential for a variety of researches, but it's still a mystery for science. It feels like scientists just know a tip of an iceberg.
ARTICLE | doi:10.20944/preprints202105.0142.v1
Subject: Medicine & Pharmacology, Allergology Keywords: Cancer Immunotherapy; Cancer Vaccine; Cancer Antigens; CRISPR-Cas9; Engineered T Cells.
Online: 7 May 2021 (11:10:13 CEST)
The mechanisms involved in immune responses to cancer have been extensively studied for several decades and, considerable attention has been paid to harnessing the immune system's therapeutic potential. Cancer immunotherapy has established itself as a promising new treatment option for a variety of cancer types. Various strategies including cancer vaccines, monoclonal antibodies (mAbs), adoptive T-cell-cancer therapy and immune test therapy have gained prominence through immunotherapy. However, it remains to be accomplished the full potential of cancer immunotherapy. In spite of having startling aspects, the cancer immunotherapies have some difficulties including the inability to effectively targeting the cancer antigens and the abnormalities in patient response. With the advancement of technology, this system has changed the genome-based immunotherapy process in the human body including generation of engineered T cells. Due to its high specificity, CRISPR-Cas9 has become a simple and flexible genome-editing tool to target nearly any genomic locus. Recently, the CD19-mediated CAR-T cell (chimeric antigen receptor T cell) therapy has opened a new avenue for the treatment of human cancer, though low efficiency is a major drawback of this process. Thus, increasing the efficiency of the CAR-T cell (engineered T cells that induce the chimeric antigen receptor) by using CRISPR-Cas9 technology could be a better weapon to fight against the cancer. In this review, we have broadly focused on the use of CRISPR-Cas9 technology for the modification of the T-cell, which can specifically recognize cancer cells and be used as immune therapeutics against cancer. We have also demonstrated the other potential strategies for the treatment of cancer.
ARTICLE | doi:10.20944/preprints202011.0723.v1
Subject: Life Sciences, Biochemistry Keywords: Fanconi anemia; gene editing; FANCA; head and neck cancer; CRISPR/Cas9
Online: 30 November 2020 (11:55:45 CET)
Fanconi anemia (FA) patients have an exacerbated risk of head and neck squamous cell carcinoma (HNSCC). Treatment is challenging as FA patients display enhanced toxicity to standard treatments, including radio/chemotherapy. Therefore better therapies as well as new disease models are urgently needed. We have used CRISPR/Cas9 editing tools in order to interrupt the human FANCA gene by the generation of insertions/deletions (indels) in exon 4 in two cancer cell lines from sporadic HNSCC having no mutation in FA-genes: CAL27 and CAL33 cells. Our approach allowed efficient editing, subsequent purification of single-cell clones, and Sanger sequencing validation at the edited locus. Clones having frameshift indels in homozygosis did not express FANCA protein and were selected for further analysis. When compared with parental CAL27 and CAL33, FANCA-mutant cell clones displayed a FA-phenotype as they i) are highly sensitive to DNA interstrand crosslink (ICL) agents such as mitomycin C (MMC) or cisplatin, ii) do not monoubiquitinate FANCD2 upon MMC treatment and therefore iii) do not form FANCD2 nuclear foci, and iv) they display increased chromosome fragility and G2 arrest after diepoxybutane (DEB) treatment. These FANCA-mutant clones display similar growth rates as their parental cells. Interestingly, mutant cells acquire phenotypes associated with more aggressive disease, such as increased migration in wound healing assays. Therefore, CAL27 and CAL33 cells with FANCA mutations are phenocopies of FA-HNSCC cells.
ARTICLE | doi:10.20944/preprints202005.0134.v1
Subject: Life Sciences, Molecular Biology Keywords: Crispr-Cas9; ACE2 gene; SARS-CoV-2; new coronavirus; COVID-19
Online: 7 May 2020 (15:26:06 CEST)
The human angiotensin-converting enzyme 2 (ACE2) has a crucial role on blood pressure control; however, ACE2 is also the primary SARS-CoV-2 (S domain) virus receptor. Inhibiting or even reducing the expression of the native ACE2 might diminish the viral entry into the cells, but may cause a failure of ACE2 biological activity, primarily in patients with comorbidities, including diabetes mellitus or hypertension. Since the ACE2 catalytic site and the SARS-Cov-2 receptor are distinct, we designed a Crispr-Cas9 model system, predicting the respective sequences for a guide RNA (gRNA) and a single-stranded oligo dideoxy nucleotide (ssODN), to introduce point mutations into the exon 1 of the human ACE2 gene, which encodes the alpha-helix, implicated on the binding of the SARS-CoV-2 envelope S protein. Protein modeling predicted that the specific substitutions of residues Phe28, Lys31, and Tyr41 for Ala at the ACE2 alpha-helix do not significantly alter ACE2 native conformation. The analysis of the impact of these mutations on ACE2 receptor function predicted a weakening of the binding of the SARS-CoV-2 protein S. An experimental genome editing of cells based on these Crispr-Cas9 elements might reduce the SARS-CoV-2 ability to enter the epithelial cell, preserving the biological activity of ACE2 enzyme.
REVIEW | doi:10.20944/preprints201710.0065.v1
Subject: Life Sciences, Genetics Keywords: hepatitis B virus; chronic hepatitis B; cccDNA; CRISPR/Cas9; gene therapy
Online: 10 October 2017 (17:59:11 CEST)
BACKGROUND: Chronic hepatitis B infected with Hepatitis B virus remains a major health concern worldwide. Despite standard interferon-α and nucleotide analogues have been shown to reduce the deterioration of liver disease among chronic hepatitis B patients, covalently closed circular DNA was still difficult to eradicate. METHODS: A literature search of Pubmed and Web of science was performed with the following key words: ‘CRISPR’, ‘CRISPR/Cas9’, ‘hepatitis B’, ‘HBV’, ‘chronic hepatitis B’ and ‘HBV cccDNA’. The information about CRISPR/Cas9 for the treatment of HBV cccDNA or hepatitis B was reviewed. RESULTS: CRISPR/Cas9 could treat hepatitis B through suppressing or clearing HBV cccDNA with different gRNAs. CONCLUSION: With the emergence of CRISPR/Cas9 (the RNA-guided clustered regulatory interspaced short palindromic repeats, CRISPR) editing technology, clearance of hepatitis B virus and better prevention of liver carcinoma seemed to be possible.
REVIEW | doi:10.20944/preprints202212.0529.v1
Subject: Life Sciences, Biotechnology Keywords: CRISPR; Cas9 ribonucleoprotein; virus-like particles; exosomes; HIV assembly and disassembly; delivery
Online: 28 December 2022 (06:11:59 CET)
Rapid progress in gene editing based on clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) has revolutionized the study of gene and genome function and genetic disease correction. While numerous genetically modified cellular and animal models have been created to understand biological processes, the clinical application of CRISPR/Cas tools has been impeded by off-targeting and delivery problems. It is generally accepted that the delivery of CRISPR in the form of a ribonucleoprotein complex (RNP) substantially reduces the time of DNA exposure to the effector nuclease, minimizing off-target effects and facilitating clinical usage. This review focuses on CRISPR/Cas RNP delivery with retro/lentiviral particles and exosomes, whose parallel production by cells transfected with viral vectors is underestimated. We critically evaluate specific mechanisms of extracellular particle formation and loading with CRISPR/Cas for each system. Additionally, the details of Cas-nanoparticle entry and uncoating, previously unappreciated in the context of gene editing efficiency, are discussed. Based on existing knowledge about the consequences of intervention in retroviral assembly, entry, or exosome formation, we outline the potential problems with CRISPR/Cas delivery using extracellular nanoparticles and ways to address them.
REVIEW | doi:10.20944/preprints202103.0277.v1
Subject: Biology, Anatomy & Morphology Keywords: CRISPR/Cas9; Disease resistance; Future perspective; Improvement of plants; Molecular scissor; Revolution
Online: 10 March 2021 (11:10:58 CET)
The growing population meet the challenge for agricultural production. CRISPR/Cas9 technology is based on plant research for the development of the new varieties as well as disease resistance crops. In addition the deletion of significant characters makes the new alleles from the CRISPR/Cas9. Recent and reliable molecular scissor for genetic engineering. The review is focused on the various application of the CRISPR/Cas9 technology in plant enhancement of plant disease resistance, stress burden in plant, nutritional improvement, and quality of crops from the CRISPR/Cas9 system. The clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein9 (cas9) is adopted from the prokaryotic type II system. CRISPR/Cas9 is simplicity and efficiency than ZENs and TALENs for the genome engineering. Due to rapid growing of the CRISPR/Cas9 system has been formulate the adaptation of many plant species. The current advancement of plants and future schemes of improve of CRISPR technology has been presented in contest of multiplex editing, knowledge on induced mutation whether the factor effect in CRISPR/Cas9 technology in plant. Remarkable perspective and challenges of CRISPR/Cas9 technology in significance of plant genetic modification.
ARTICLE | doi:10.20944/preprints202008.0619.v1
Subject: Biology, Plant Sciences Keywords: CRISPR-Cas9; course-based undergraduate research experience; CURE; remote learning; plant biology
Online: 27 August 2020 (12:29:53 CEST)
Gene editing tools such as CRISPR-Cas9 have created unprecedented opportunities for genetic studies in plants and animals. We designed a course-based undergraduate research experience (CURE) to train introductory biology students in the concepts and implementation of gene editing technology as well as develop their soft skills in data management and scientific communication. We present two versions of the course that can be implemented with twice-weekly meetings over a five-week period. In the remote-learning version, students perform homology searches, design guide RNAs and primers, and learn the principles of molecular cloning. This version is appropriate when access to laboratory equipment or in-person instruction is limited, such as closures that have occurred in response to the Covid-19 pandemic. In the in-person version, students design guide RNAs, clone CRISPR-Cas9 constructs, and perform genetic transformation of the model plant Arabidopsis thaliana. The highly parallel nature of the CURE makes it possible to target dozens to hundreds of genes, depending on the number of course sections available. Applying this approach in a sensitized mutant background enables focused reverse genetic screens for genetic suppressors or enhancers. The course can be readily adapted to other organisms or projects that employ gene editing.
ARTICLE | doi:10.20944/preprints201811.0279.v1
Subject: Life Sciences, Cell & Developmental Biology Keywords: copper importers CTR1 and DMT1; CRICPR-Cas9; cisplatin; silver; signaling; copper homeodynamics
Online: 12 November 2018 (10:05:01 CET)
Copper, the highly toxicity micronutrient, plays two essential roles: it is a catalytic and structural cofactor for Cu-dependent enzymes, and it acts as a secondary messenger. In the cells, copper is imported by CTR1, a transmembrane high-affinity copper importer, and DMT1 (divalent metal transporter). In cytosol, enzyme-specific chaperones receive copper from CTR1 C-terminus and deliver it to their apoenzymes. DMT1 cannot be a donor of catalytic copper because it does not have cytosol domain which is required for copper transfer to the Cu-chaperons and following to cuproenzymes. Here we assume that DMT1 can mediate copper way required for regulatory copper pool. To verify this thought, we used CRISPR/Cas9 to generate H1299 cell line with CTR1 or DMT1 single knockout (KO) and CTR1/DMT1 double knockout (DKO). To confirm KOs of the genes qRT-PCR were used. Two independent clones for each gene were selected for further studies. In CTR1-KO cells, expression of the DMT1 gene was significantly increased. In subcellular compartments, copper concentration decreased dramatically in DKO cells. CTR1-KO cells, but not DMT1-KO, demonstrated reduced sensitivity to cisplatin and silver ions, agents that enter the cell through CTR1. The expression of genes, whose protein products require copper: HIF1α, XIAP, COMMD1, CCS, Cp, but not SOD1 and NF-kB, changed their level. Perhaps these data will help to understand how the disturbances of copper homeodynamics lead to the development of neurodegenerative and oncological disorders. Possibility of using CTR1 KO and DMT1 KO cells to study homeodynamics of catalytic and signaling copper selectively is discussed.
REVIEW | doi:10.20944/preprints202209.0117.v1
Subject: Life Sciences, Biotechnology Keywords: abiotic stress tolerance; base editing; CRISPR/Cas9; crop production; gene editing; prime editing
Online: 8 September 2022 (03:31:39 CEST)
Abiotic stresses, including drought, salinity, cold, heat, and heavy metals, extensively reduce global agricultural production. Approaches such as conventional breeding and transgenic breeding have been widely used to cope with these environmental stresses. The clustered regularly interspaced short palindromic repeat- Cas (CRISPR/Cas) based gene-editing tool has revolutionized due to its simplicity, accessibility, adaptability, flexibility, and wide applicability. This system has a great potential to build up crop varieties with enhanced tolerance against abiotic stresses. In this review, we summarize the most recent findings on understanding the mechanism of abiotic stress response in plants and the application of CRISPR/Cas mediated gene-editing system towards enhanced tolerance to drought, salinity, cold, heat, and heavy metals stresses. Furthermore, in this review, we highlighted the recent advancements in prime editing and base editing tools for crop improvement.
REVIEW | doi:10.20944/preprints202201.0137.v1
Subject: Life Sciences, Immunology Keywords: Adoptive T cell therapy; CAR T cells; CRISPR/Cas9; gene modifications; T cells
Online: 11 January 2022 (12:57:40 CET)
Adaptive T cell immunotherapy holds great promise for the successful treatment of leukemia as well as other types of cancers. More recently, it was also shown to be an effective treatment option for chronic virus infections in immunosuppressed patients. Autologous or allogeneic T cells used for immunotherapy are usually genetically modified to express novel T cell or chimeric antigen receptors. The production of such cells was significantly simplified with the CRISPR/Cas system allowing deletion or insertion of novel genes at specific locations within the genome. In this review, we describe recent methodological breakthroughs important for the conduction of these genetic modifications, summarize crucial points to be considered when conducting such experiments, and highlight the potential pitfalls of these approaches.
ARTICLE | doi:10.20944/preprints202104.0474.v1
Subject: Life Sciences, Biochemistry Keywords: CRISPR/Cas9; knockout; rescue; desiccation tolerance; anhydrobiosis; Polypedilum vanderplanki; HSF1; insect cell; Pv11
Online: 19 April 2021 (12:17:34 CEST)
Pv11, an insect cell line established from the midge Polypedilum vanderplanki, is capable of ametabolic desiccation tolerance, so-called anhydrobiosis. We previously discovered that heat shock factor 1 (HSF1) contributes to the acquisition of desiccation tolerance by Pv11 cells, but the mechanistic details have yet to be elucidated. Here, by analyzing the gene expression profiles of newly established HSF1-knockout and -rescue cell lines, we show that HSF1 has a genome-wide effect on gene regulation in Pv11. HSF1-knockout cells exhibit a reduced desiccation survival rate, but this is completely restored in HSF1-rescue cells. By comparing mRNA profiles of the two cell lines, we reveal that HSF1 induces anhydrobiosis-related genes, especially genes encoding late embryogenesis abundant proteins and thioredoxins, but represses a group of genes involved in basal cellular processes, thus promoting an ametabolic state in the cell. In addition, HSF1 binding motifs are enriched in the promoters of anhydrobiosis-related genes and we demonstrate binding of HSF1 to these promoters by ChIP-qPCR. Thus, HSF1 directly regulates the transcription of anhydrobiosis-related genes and consequently plays a pivotal role in the induction of anhydrobiotic ability in Pv11 cells.
ARTICLE | doi:10.20944/preprints202010.0102.v1
Subject: Life Sciences, Biochemistry Keywords: lncRNA; LINC00961; SPAAR; scRNASeq; CRISPR/Cas9; cardiovascular physiology; fetal growth restriction; myocardial infarction
Online: 5 October 2020 (17:47:46 CEST)
Long non-coding RNAs (lncRNAs) have structural and functional roles in development and disease. We have previously shown that the LINC00961/SPAAR locus regulates endothelial cell function, and that both the lncRNA and micropeptide counter-regulate angiogenesis. To assess human cardiac cell SPAAR expression we mined a publicly available scRNSeq dataset and confirmed LINC00961 locus expression and hypoxic response in a murine endothelial cell line. We investigated post-natal growth and development, basal cardiac function, the cardiac functional response and tissue-specific response to myocardial infarction. To investigate the contribution of the LINC00961/SPAAR locus to determination of longitudinal growth, cardiac function, and response to myocardial infarction, we used a novel CRISPR/Cas9 locus knockout mouse line. Data mining suggested that SPAAR is predominantly expressed in human cardiac endothelial cells and fibroblasts, while murine LINC00961 expression is hypoxia-responsive in mouse endothelial cells. LINC00961-/- mice displayed a sex-specific delay in longitudinal growth and development, smaller left ventricular systolic and diastolic areas and volumes, and greater risk area following myocardial infarction compared with wildtype littermates. These data suggest a role for the LINC00961/SPAAR locus in cardiac endothelial cell and fibroblast cell function and hypoxic-response, and in growth and development, and basal cardiovascular function in adulthood.
REVIEW | doi:10.20944/preprints202009.0490.v1
Subject: Biology, Other Keywords: base editing; prime editing; ABE; SCD; sickle cell disease; sickle cell anemia; CRISPR; Cas9
Online: 21 September 2020 (04:23:21 CEST)
Sickle cell disease is characterized by stiff, “sickled” red blood cells that have difficulty moving through the bloodstream and do not efficiently carry oxygen. It is an inherited disease with severely limited treatment options, and is caused by a point mutation. Its prevalence in black and brown communities makes the already limited treatment options even less accessible. Base editing and prime editing are two relatively recent discoveries in the field of genome editing and were developed after the groundbreaking discovery of the CRISPR Cas9 system. While not fully tested, they hold a lot of promise in providing alternative treatment options for sickle cell disease. Both editing systems are able to install individual point mutations in the beta globin gene, which is where the sickle cell mutation occurs, and can thus cure sickle cell disease (in theory). In this paper we outline the mechanisms of CRISPR-Cas9 systems and base and prime editing, and provide insight into how to apply them to treat SCD. Further investigation should be done on specific editing systems and designs to use to ensure optimal treatment of SCD.
ARTICLE | doi:10.20944/preprints201810.0451.v1
Subject: Life Sciences, Molecular Biology Keywords: CTCF; tumour suppressor gene; haploinsufficiency; zinc finger; CRISPR/Cas9; cancer; endometrial cancer; gene editing
Online: 19 October 2018 (11:29:01 CEST)
CCCTC-binding factor (CTCF) is a conserved transcription factor that performs diverse roles in transcriptional regulation and chromatin architecture. Cancer genome sequencing reveals diverse acquired mutations in CTCF, which we have shown, functions as a tumour suppressor gene. While CTCF is essential for embryonic development, little is known of its absolute requirement in somatic cells and the consequences of CTCF haploinsufficiency. We examined the consequences of CTCF depletion in immortalised human and mouse cells using shRNA knockdown and CRISPR/Cas9 genome editing and examined the growth and development of heterozygous Ctcf (Ctcf+/-) mice. We also analysed the impact of CTCF haploinsufficiency by examining gene expression changes in CTCF-altered endometrial carcinoma. Knockdown and CRISPR/Cas9-mediated editing of CTCF reduced the cellular growth and colony-forming ability of K562 cells. CTCF knockdown also induced cell cycle arrest and a pro-survival response to apoptotic insult. However, in p53 shRNA-immortalised Ctcf+/- MEFs we observed the opposite: increased cellular proliferation, colony formation, cell cycle progression and decreased survival after apoptotic insult compared to wild type MEFs. CRISPR/Cas9-mediated targeting in Ctcf+/- MEFs revealed a predominance of in-frame microdeletions in Ctcf in surviving clones, however protein expression could not be ablated. Examination of CTCF mutations in endometrial cancers showed locus-specific alterations in gene expression due to CTCF haploinsufficiency, in concert with downregulation of tumour suppressor genes and upregulation of estrogen-responsive genes. Depletion of CTCF expression imparts a dramatic negative effect on normal cell function. However, CTCF haploinsufficiency can have growth-promoting effects consistent with known cancer hallmarks in the presence of additional genetic hits. Our results confirm the absolute requirement for CTCF expression in somatic cells and provide definitive evidence of CTCF’s role as a haploinsufficient tumour suppressor gene. CTCF genetic alterations in endometrial cancer indicate that gene dysregulation is a likely consequence of CTCF loss, contributing to, but not solely driving cancer growth.
ARTICLE | doi:10.20944/preprints202212.0442.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: P21; CDKN1A; glioblastoma; senescence; cancer senescence; gene overexpression; gene knock-in; CRISPR/Cas9; dCas; dCas-VPR
Online: 23 December 2022 (04:10:22 CET)
High-grade gliomas are the most common and aggressive adult primary brain tumors with a median survival of only 12-15 months. Current standard therapy consists of maximal safe surgical resection followed by DNA-damaging agents, such as irradiation and chemotherapy that can delay but not prevent inevitable recurrence. Some have interpreted glioma recurrence as evidence of glioma stem cells which persist in a relatively quiescent state after irradiation and chemotherapy, before the ultimate cell cycle re-entry and glioma recurrence. Conversely, latent cancer cells with a therapy-induced senescent phenotype have been shown to escape senescence, giving rise to more aggressive stem-like tumor cells than those present in the original tumor. Therefore, approaches are needed to either eliminate or keep these glioma-initiating cells in a senescent state for a longer time to prolong survival. In our current study, we demonstrate that the radiation-induced cell cycle inhibitor P21 can provide a powerful route to induce cell death in short-term explants of PDXs derived from three molecularly diverse human gliomas. Additionally, cells not killed by P21 overexpression were maintained in a stable senescent state for longer than control cells. Collectively, these data suggest that P21 activation may provide an attractive therapeutic target to improve therapeutic outcomes.
Subject: Life Sciences, Biochemistry Keywords: synthetic biology; CRISPR; Cas9; biotechnology; biodesign; nickase; base editing; prime editing; genome editing; ethics; responsible innovation
Online: 1 October 2020 (08:38:22 CEST)
The RNA-guided endonuclease system CRISPR-Cas9 has been extensively modified since its discovery, allowing its capabilities to be extending far beyond double-stranded cleavage to high fidelity insertions, deletions, and single base edits. Such innovations have been possible due to the modular architecture of CRISPR-Cas9 and the robustness of its component parts to modifications and the fusion of new functional elements. Here, we review the broad toolkit of CRISPR-Cas9-based systems now available for diverse genome editing tasks. We provide an overview of their core molecular structure and mechanism and distil the design principles used to engineer their diverse functionalities. We end by looking beyond the biochemistry and towards the societal and ethical challenges that these CRISPR-Cas9 systems face if their transformative capabilities are to be deployed in a safe and acceptable manner.
ARTICLE | doi:10.20944/preprints202106.0169.v1
Subject: Life Sciences, Biochemistry Keywords: melanoma initiating cells; CD133; drug resistance; apoptosis; caspase activation; CRISPR-Cas9 knockout; AKT; BAD; BCL-2 family
Online: 7 June 2021 (12:11:10 CEST)
Malignant melanoma is a lethal skin cancer containing melanoma-initiating cells (MIC), implicated in tumorigenesis, invasion, and drug resistance, and characterized by elevated expression of stem cell markers, such as CD133. We previously showed that siRNA knockdown of CD133 enhances apoptosis induced by the MEK inhibitor trametinib in melanoma cells. The current study investigates underlying mechanisms of CD133’s anti-apoptotic activity in patient-derived BAKP and POT cells, harboring difficult-to-treat NRASQ61K and NRASQ61R drivers, after CRISPR-Cas9 CD133 knockdown or Dox-inducible expression of CD133. To maintain stable expression of CD133, MACS-sorted CD133(+) positive cells were expanded by ROCK-mediated conditional reprogramming of BAKP melanoma cells (BAKR). BAKR showed increased survival via reduced apoptosis after exposure to trametinib or DTIC, compared to BAKP. CRISPR-Cas9- mediated CD133 knockdown in BAKR cells (BAKR-T3) re-sensitized the cells, while CRISPR-Cas9 knockdown of CD133 in parental BAKP and POT cells even further increased trametinib-induced apoptosis (cleaved PARP) by reducing levels of anti-apoptotic BCL-xL, p-AKT, and p-BAD, and increasing pro-apoptotic BAD and active BAX. Dox-induced CD133 overexpression had the opposite effect, and blocked trametinib-induced apoptosis in both cell lines, coincident with elevated p-AKT, p-BAD, BCL-2 and BCL-xL and decreased levels of the active form of BAX and caspases-3 and -9. The roles of CD133 in AKT and BAD phosphorylation, or in the upregulation of anti-apoptotic BCL-2 family members, was further investigated by AKT knockout with siRNA, or inhibition of BCL-2 family members with navitoclax (ABT-263). Similar to CD133 knockdown, AKT1/2 siRNA knockdown in BAKP cells also reduced p-BAD. CD133 knockdown (T3)-mediated reduction of pBAD levels was equivalent in AKT-knockdown or AKT control cells indicating that CD133 may be upstream of AKT signaling. In BAKP cells treated with trametinib and/or ABT-263, effects of ABT-263 mirrored CD133 knockdown, since levels of active BAX and cleaved-PARP in BAKP-SC (CD133-) cells increased to the same level as that exhibited by BAKP-T3 cells (CD133+). CD133 may therefore activate a survival pathway where 1) increased phosphorylation of AKT induces 2) phosphorylation and inactivation of BAD, 3) decrease in the active form of BAX, and 4) reduction in caspase-mediated PARP cleavage, indicating apoptosis suppression leading to drug resistance in melanomas. Targeting survival pathways by which CD133 may confer chemoresistance in MICs can contribute to development of more effective treatments for patients with high-risk melanoma.
REVIEW | doi:10.20944/preprints201810.0010.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: Gene therapy, gene editing, CRISPR/Cas9, Cas12a, dual AAV, triple AAV, clinical trials, retina, hereditary retinal dystrophies
Online: 1 October 2018 (13:52:23 CEST)
Recently, there have been revolutions in the development of both gene therapy and genome surgical treatments for inherited diseases. Much of this progress has been centered around hereditary retinal dystrophies, because the eye is an immune-privileged and anatomically ideal target. Gene therapy treatments, already demonstrated to be safe and efficacious in numerous clinical trials, are benefitting from the development of new viral vectors, such as dual and triple AAVs. CRISPR/Ca9, which revolutionized the field of gene editing, is being adapted into more precise “high fidelity” and catalytically dead variants. New CRISPR endonucleases, such as CjCas9 and Cas12a, are generating excitement in the field as well. Stem cell therapy has emerged as a promising alternative, allowing human embryo derived stem cells and induced pluripotent stem cells to be edited precisely in vitro and then reintroduced into the body. This article highlights recent progress made in gene therapy and genome surgery for retinal disorders, and it provides an update on precision medicine FDA treatment trials.
REVIEW | doi:10.20944/preprints201907.0211.v2
Subject: Medicine & Pharmacology, Pathology & Pathobiology Keywords: HIV-1; CRISPR-Cas9; T-cells; lipid nanoparticles; gut-associated-lymphoid tissue; Co-receptors; Probiotics; GI Tract,; Gene Editing
Online: 13 April 2020 (10:57:52 CEST)
HIV-1 is a complicated and perplexing virus. It infects T cells, reverse transcribes its RNA into DNA, utilizes its host DNA machinery to replicate its HIV-DNA, translates the HIV-DNA into proteins, assembles itself for a budding escape from the T cell, and rapidly mutates its conformation. Partially, due to its complexity, there remains no cure for HIV or AIDs. However, recently with the discovery of TALENs, the use of zinc fingers, and most of all the applications of CRISPR-Cas9 technology, has given researchers new hope in finding alternative gene therapies and treatments for diseases. With more focus on CRISPR-Cas9, this new and novel technology uses a guiding RNA, sgRNA, to lead a Cas9 nuclease to its target for deletion or to change that DNA site. CRISPR-Cas9 can delete point mutations and multiple DNA sites. Because CRISPR can alter DNA sequences, several scientists have conducted research into CRISPR, possibly treating more diseases such as cancer, diabetes, and even HIV. HIV-1 drew the focus of a researcher named Dr. Ebina in 2013 when he was the first to design and apply CRISPR-Cas9 to genes found in the binding sites of HIV-1, inhibiting HIV-1 gene expression. Since 2013, several other researchers have blocked HIV replication and infection through CRISPR-Cas9 targeting the receptors of T cells called the CC chemokine receptor 5 or CCR5. HIV-1 binds to the CD4 receptor of T cells, which consists of co-receptors CCR5 and CXCR4. If CCR5 expression can be removed, the HIV virus cannot bind to T-cells, blocking the initial attachment stage, and discontinuing the infection. However, there remain obstacles and issues for the CRISPR deletion of CCR5 for treating HIV-1. The issues include: 1) finding new and safe methods of CRISPR-Cas9 delivery, 2) clearing the latent HIV reservoirs, 3) improving the sgRNA design to avoid off-target mutations or deletions, and 4) effectively analyze the viral escape of HIV from CRISPR-Cas9 modifications. Therefore, the purpose of this review is to discuss possible techniques for removing the obstacles that can lessen the potential of CRISPR to delete CCR5, repressing HIV-1 into long-term remission or a functional cure.
ARTICLE | doi:10.20944/preprints202005.0001.v1
Subject: Life Sciences, Cell & Developmental Biology Keywords: CRISPR-Cas9; high-content screening (HCS); fluorescent-activated cell sorting (FACS); Parkinson's disease (PD); patient-derived iPS; single-cell clones; isogenic cell lines; SNCA; alpha-synuclein; A30P
Online: 2 May 2020 (11:20:20 CEST)
The generation of isogenic induced pluripotent stem cell (iPSC) lines using CRISPR-Cas9 technology is a technically challenging, time-consuming process with variable efficiency. Here we use fluorescence-activated cell sorting (FACS) to sort biallelic CRISPR-Cas9 edited single-cell iPS clones into high-throughput 96-well microtiter plates. We used high-content screening (HCS) technology and generated an in-house developed algorithm to select the correctly edited isogenic clones for continued expansion and validation. In our model we have gene-corrected the iPSCs of a Parkinson’s disease (PD) patient carrying the autosomal dominantly inherited heterozygous c.88G>C mutation in the SNCA gene, which leads to the pathogenic p.A30P form of the alpha-synuclein protein. Undertaking a PCR restriction-digest mediated clonal selection strategy prior to sequencing, we were able to post-sort validate each isogenic clone using a quadruple screening strategy. Subsequent transfection with mRNA encoding excision-only transposase allows for the generation of footprint-free isogenic iPSC lines. These monoclonal isogenic iPSC lines retain a normal molecular genotype, express pluripotency markers and have the ability to differentiate into the three germ layers. This combinatory approach of FACS, HCS and post-sorted restriction digestion facilitates the generation of isogenic cell lines for disease modelling to be scaled-up on an automated platform.
REVIEW | doi:10.20944/preprints201912.0385.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: dilated cardiomyopathy (DCM); hypertrophic cardiomyopathy (HCM); restrictive cardiomyopathy (RCM); arrhythmogenic right ventricular cardiomyopathy (ARVC); left ventricular non-compaction cardiomyopathy (LVNC); Duchenne muscular dystrophy; dystrophin; genome editing; CRISPR/Cas9; Cpf1 (Cas12a)
Online: 29 December 2019 (13:41:48 CET)
Cardiomyopathies are diseases of heart muscle, a significant percentage of which are genetic in origin. Cardiomyopathies can be classified as dilated, hypertrophic, restrictive, arrhythmogenic right ventricular or left ventricular non-compaction, although mixed morphologies are possible. A subset of neuromuscular disorders, notably Duchenne and Becker muscular dystrophies, are also characterized by cardiomyopathy aside from skeletal myopathy. The global burden of cardiomyopathies is certainly high, necessitating further research and novel therapies. Genome editing tools, which include zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR) systems have emerged as increasingly important technologies in studying this group of cardiovascular disorders. In this review, we discuss the applications of genome editing in the understanding and treatment of cardiomyopathy. We also describe recent advances in genome editing that may help improve these applications, and some future prospects for genome editing in cardiomyopathy treatment.
REVIEW | doi:10.20944/preprints201811.0018.v1
Subject: Life Sciences, Genetics Keywords: Duchenne muscular dystrophy (DMD); CRISPR/Cas9; exon skipping therapy; gene editing; human induced pluripotent stem cells (hiPSCs); immortalized patient muscle cells; mdx mice; humanized dystrophic mouse models; deltaE50-MD dog model
Online: 2 November 2018 (05:14:23 CET)
Duchenne muscular dystrophy (DMD) is a fatal X-linked recessive neuromuscular disease prevalent in 1 in 3500 to 5000 males worldwide. As a result of mutations that interrupt the reading frame of the dystrophin gene (DMD), DMD is characterized by a loss of dystrophin protein which leads to decreased muscle membrane integrity, which increases susceptibility to degeneration. CRISPR/Cas9 technology has garnered interest as an avenue for DMD therapy due to its potential for permanent exon skipping, which can restore the disrupted DMD reading frame in DMD and lead to dystrophin restoration. An RNA-guided DNA endonuclease system, CRISPR/Cas9 allows for the targeted editing of specific sequences in the genome. The efficacy and safety of CRISPR/Cas9 as a therapy for DMD has been evaluated by numerous studies in vitro and in vivo, with varying rates of success. Despite the potential of CRISPR/Cas9-mediated gene editing for the long-term treatment of DMD, its translation into the clinic is currently challenged by issues such as off-targeting, immune response activation, and sub-optimal in vivo delivery. Its nature as being mostly a personalized form of therapy also limits applicability to DMD patients, who exhibit a wide spectrum of mutations. This review summarizes the various CRISPR/Cas9 strategies that have been tested in vitro and in vivo for the treatment of DMD. Perspectives on the approach will be provided, and the challenges faced by CRISPR/Cas9 in its road to the clinic will be briefly discussed.