Electroporation and genetic supply of Cas9 increase the generation efficiency of CRISPR/Cas9 knock-in alleles in C57BL/6J mouse zygotes

DNA- and Selectable-Marker-Free Genome-Editing System Using Zygotes from Recalcitrant Maize Inbred B73

Genome-editing tools such as the clustered regularly interspaced short palindromic repeats/Cas9 (CRISPR/Cas9) system have become essential tools for increasing the efficiency and accuracy of plant breeding. Using such genome-editing tools on maize, one of the most important cereal crops of the world, will greatly benefit the agriculture and the mankind. Conventional genome-editing methods typically used for maize involve insertion of a Cas9-guide RNA expression cassette and a selectable marker in the genome DNA; however, using such methods, it is essential to eliminate the inserted DNA cassettes to avoid legislative concerns on gene-modified organisms. Another major hurdle for establishing an efficient and broadly applicable DNA-free genome-editing system for maize is presented by recalcitrant genotypes/cultivars, since cell/tissue culture and its subsequent regeneration into plantlets are crucial for producing transgenic and/or genome-edited maize. In this study, to establish a DNA-free genome-editing system for recalcitrant maize genotypes/cultivars, Cas9-gRNA ribonucleoproteins were directly delivered into zygotes isolated from the pollinated flowers of the maize-B73 cultivar. The zygotes successfully developed and were regenerated into genome-edited plantlets by co-culture with phytosulfokine, a peptide phytohormone. The method developed herein made it possible to obtain DNA- and selectable-marker-free genome-edited recalcitrant maize genotypes/cultivars with high efficiency. This method can advance the molecular breeding of maize and other important cereals, regardless of their recalcitrant characteristics.

Heterozygous THBS2 pathogenic variant causes Ehlers-Danlos syndrome with prominent vascular features in humans and mice

Ehlers-Danlos syndromes (EDS) are a group of connective tissue disorders caused by mutations in collagen and collagen-interacting genes. We delineate a novel form of EDS with vascular features through clinical and histopathological phenotyping and genetic studies of a three-generation pedigree, displaying an apparently autosomal dominant phenotype of joint hypermobility and frequent joint dislocations, atrophic scarring, prolonged bleeding time and age-related aortic dilatation and rupture. Coagulation tests as well as platelet counts and function were normal. Reticular dermis displayed highly disorganized collagen fibers and transmission electron microscopy (TEM) revealed abnormally shaped fibroblasts and endothelial cells, with high amount and irregular shape of extracellular matrix (ECM) substance, especially near blood vessels. Genetic analysis unraveled a heterozygous mutation in THBS2 (NM_003247.5:c.2686T>C, p.Cys896Arg). We generated CRISPR/Cas9 knock-in (KI) mice, bearing the heterozygous human mutation in the mouse ortholog. The KI mice demonstrated phenotypic traits correlating with those observed in the human subjects, as evidenced by morphologic, histologic, and TEM analyses, in conjunction with bleeding time assays. Our findings delineate a novel form of human EDS with classical-like elements combined with vascular features, caused by a heterozygous THBS2 missense mutation. We further demonstrate a similar phenotype in heterozygous THBS2Cys896Arg KI mice, in line with previous studies in Thbs2 homozygous null-mutant mice. Notably, THBS2 encodes Thrombospondin-2, a secreted homotrimeric matricellular protein that directly binds the ECM-shaping Matrix Metalloproteinase 2 (MMP2), mediating its clearance. THBS2 loss-of-function attenuates MMP2 clearance, enhancing MMP2-mediated proteoglycan cleavage, causing ECM abnormalities similar to those seen in the human and mouse disease we describe.

Increasing Knockin Efficiency in Mouse Zygotes by Transient Hypothermia

Integration of a point mutation to correct or edit a gene requires the repair of the CRISPR-Cas9-induced double-strand break by homology-directed repair (HDR). This repair pathway is more active in late S and G2 phases of the cell cycle, whereas the competing pathway of nonhomologous end-joining (NHEJ) operates throughout the cell cycle. Accordingly, modulation of the cell cycle by chemical perturbation or simply by the timing of gene editing to shift the editing toward the S/G2 phase has been shown to increase HDR rates. Using a traffic light reporter in mouse embryonic stem cells and a fluorescence conversion reporter in human-induced pluripotent stem cells, we confirm that a transient cold shock leads to an increase in the rate of HDR, with a corresponding decrease in the rate of NHEJ repair. We then investigated whether a similar cold shock could lead to an increase in the rate of HDR in the mouse embryo. By analyzing the efficiency of gene editing using single nucleotide polymorphism changes and loxP insertion at three different genetic loci, we found that a transient reduction in temperature after zygote electroporation of CRISPR-Cas9 ribonucleoprotein with a single-stranded oligodeoxynucleotide repair template did indeed increase knockin efficiency, without affecting embryonic development. The efficiency of gene editing with and without the cold shock was first assessed by genotyping blastocysts. As a proof of concept, we then confirmed that the modified embryo culture conditions were compatible with live births by targeting the coat color gene tyrosinase and observing the repair of the albino mutation. Taken together, our data suggest that a transient cold shock could offer a simple and robust way to improve knockin outcomes in both stem cells and zygotes.

An oocyte-specific Cas9-expressing mouse for germline CRISPR/Cas9-mediated genome editing

Cas9 transgenes can be employed for genome editing in mouse zygotes. However, using transgenic instead of exogenous Cas9 to produce gene-edited animals creates unique issues including ill-defined transgene integration sites, the potential for prolonged Cas9 expression in transgenic embryos, and increased genotyping burden. To overcome these issues, we generated mice harboring an oocyte-specific, Gdf9 promoter driven, Cas9 transgene (Gdf9-Cas9) targeted as a single copy into the Hprt1 locus. The X-linked Hprt1 locus was selected because it is a defined integration site that does not influence transgene expression, and breeding of transgenic males generates obligate transgenic females to serve as embryo donors. Using microinjections and electroporation to introduce sgRNAs into zygotes derived from transgenic dams, we demonstrate that Gdf9-Cas9 mediates genome editing as efficiently as exogenous Cas9 at several loci. We show that genome editing efficiency is independent of transgene inheritance, verifying that maternally derived Cas9 facilitates genome editing. We also show that paternal inheritance of Gdf9-Cas9 does not mediate genome editing, confirming that Gdf9-Cas9 is not expressed in embryos. Finally, we demonstrate that off-target mutagenesis is equally rare when using transgenic or exogenous Cas9. Together, these results show that the Gdf9-Cas9 transgene is a viable alternative to exogenous Cas9.

Past, present, and future of CRISPR genome editing technologies

Genome editing has been a transformative force in the life sciences and human medicine, offering unprecedented opportunities to dissect complex biological processes and treat the underlying causes of many genetic diseases. CRISPR-based technologies, with their remarkable efficiency and easy programmability, stand at the forefront of this revolution. In this Review, we discuss the current state of CRISPR gene editing technologies in both research and therapy, highlighting limitations that constrain them and the technological innovations that have been developed in recent years to address them. Additionally, we examine and summarize the current landscape of gene editing applications in the context of human health and therapeutics. Finally, we outline potential future developments that could shape gene editing technologies and their applications in the coming years.

Donor template delivery by recombinant adeno-associated virus for the production of knock-in mice

BACKGROUND

The ability of recombinant adeno-associated virus to transduce preimplantation mouse embryos has led to the use of this delivery method for the production of genetically altered knock-in mice via CRISPR-Cas9. The potential exists for this method to simplify the production and extend the types of alleles that can be generated directly in the zygote, obviating the need for manipulations of the mouse genome via the embryonic stem cell route.

RESULTS

We present the production data from a total of 13 genetically altered knock-in mouse models generated using CRISPR-Cas9 electroporation of zygotes and delivery of donor repair templates via transduction with recombinant adeno-associated virus. We explore the efficiency of gene targeting at a total of 12 independent genetic loci and explore the effects of allele complexity and introduce strategies for efficient identification of founder animals. In addition, we investigate the reliability of germline transmission of the engineered allele from founder mice generated using this methodology. By comparing our production data against genetically altered knock-in mice generated via gene targeting in embryonic stem cells and their microinjection into blastocysts, we assess the animal cost of the two methods.

CONCLUSIONS

Our results confirm that recombinant adeno-associated virus transduction of zygotes provides a robust and effective delivery route for donor templates for the production of knock-in mice, across a range of insertion sizes (0.9-4.7 kb). We find that the animal cost of this method is considerably less than generating knock-in models via embryonic stem cells and thus constitutes a considerable 3Rs reduction.

Optimising Electroporation Condition for CRISPR/Cas-Mediated Knockout in Zona-Intact Buffalo Zygotes

Somatic cell nuclear transfer or cytoplasm microinjection has widely been used to produce genome-edited farm animals; however, these methods have several drawbacks which reduce their efficiency. In the present study, we describe an easy adaptable approach for the introduction of mutations using CRISPR-Cas9 electroporation of zygote (CRISPR-EP) in buffalo. The goal of the study was to determine the optimal conditions for an experimental method in which the CRISPR/Cas9 system is introduced into in vitro-produced buffalo zygotes by electroporation. Electroporation was performed using different combinations of voltage, pulse and time, and we observed that the electroporation in buffalo zygote at 20 V/mm, 5 pulses, 3 msec at 10 h post insemination (hpi) resulted in increased membrane permeability and higher knockout efficiency without altering embryonic developmental potential. Using the above parameters, we targeted buffalo POU5F1 gene as a proof of concept and found no variations in embryonic developmental competence at cleavage or blastocyst formation rate between control, POU5F1-KO, and electroporated control (EC) embryos. To elucidate the effect of POU5F1-KO on other pluripotent genes, we determined the relative expression of SOX2, NANOG, and GATA2 in the control (POU5F1 intact) and POU5F1-KO-confirmed blastocyst. POU5F1-KO significantly (p ≤ 0.05) altered the expression of SOX2, NANOG, and GATA2 in blastocyst stage embryos. In conclusion, we standardized an easy and straightforward protocol CRISPR-EP method that could be served as a useful method for studying the functional genomics of buffalo embryos.

Efficient DNA knock-in using AAV-mediated delivery with 2-cell embryo CRISPR-Cas9 electroporation

Recent advances in CRISPR-Cas genome editing technology have been instrumental in improving the efficiency to produce genetically modified animal models. In this study we have combined four very promising approaches to come up with a highly effective pipeline to produce knock-in mouse and rat models. The four combined methods include: AAV-mediated DNA delivery, single-stranded DNA donor templates, 2-cell embryo modification, and CRISPR-Cas ribonucleoprotein (RNP) electroporation. Using this new combined approach, we were able to produce successfully targeted knock-in rat models containing either Cre or Flp recombinase sequences with knock-in efficiencies over 90%. Furthermore, we were able to produce a knock-in mouse model containing a Cre recombinase targeted insertion with over 50% knock-in efficiency directly comparing efficiencies to other commonly used approaches. Our modified AAV-mediated DNA delivery with 2-cell embryo CRISPR-Cas9 RNP electroporation technique has proven to be highly effective for generating both knock-in mouse and knock-in rat models.

CRISPR/Cas9-based gene-editing technology for sickle cell disease

Sickle cell disease (SCD) is the most common monogenic hematologic disorder and is essentially congenital hemolytic anemia caused by an inherited point mutation in the β-globin on chromosome 11. Although the genetic basis of SCD was revealed as early as 1957, treatment options for SCD have been very limited to date. Hematopoietic stem cell transplantation (HSCT) was thought to hold promise as a cure for SCD, but the available donors were still only 15% useful. Gene therapy has advanced rapidly into the 21st century with the promise of a cure for SCD, and gene editing strategies based on the cluster-based regularly interspaced short palindromic repeat sequence (CRISPR)/Cas9 system have revolutionized the field of gene therapy by precisely targeting genes. In this paper, we review the pathogenesis and therapeutic approaches of SCD, briefly summarize the delivery strategies of CRISPR/Cas9, and finally discuss in depth the current status, application barriers, and solution directions of CRISPR/Cas9 in SCD. Through the review in this paper, we hope to provide some references for gene therapy in SCD.

A Review of CRISPR Tools for Treating Usher Syndrome: Applicability, Safety, Efficiency, and In Vivo Delivery

This review considers research into the treatment of Usher syndrome, a deaf-blindness syndrome inherited in an autosomal recessive manner. Usher syndrome mutations are markedly heterogeneous, involving many different genes, and research grants are limited due to minimal patient populations. Furthermore, gene augmentation therapies are impossible in all but three Usher syndromes as the cDNA sequence exceeds the 4.7 kb AAV packaging limit. It is, therefore, vital to focus research efforts on alternative tools with the broadest applicability. The CRISPR field took off in recent years following the discovery of the DNA editing activity of Cas9 in 2012. New generations of CRISPR tools have succeeded the original CRISPR/Cas9 model to enable more sophisticated genomic amendments such as epigenetic modification and precise sequence alterations. This review will evaluate the most popular CRISPR tools to date: CRISPR/Cas9, base editing, and prime editing. It will consider these tools in terms of applicability (in relation to the ten most prevalent USH2A mutations), safety, efficiency, and in vivo delivery potential with the intention of guiding future research investment.

Research and Therapeutic Approaches in Stem Cell Genome Editing by CRISPR Toolkit

The most widely used genome editing toolkit is CRISPR (clustered regularly interspaced short palindromic repeats). It provides the possibility of replacing and modifying DNA and RNA nucleotides. Furthermore, with advancements in biological technology, inhibition and activation of the transcription of specific gene(s) has become possible. Bioinformatics tools that target the evolution of CRISPR-associated protein 9 (Cas9) turn this protein into a vehicle that is specific for a DNA or RNA region with single guide RNA (sgRNA). This toolkit could be used by researchers to investigate the function of stem cell gene(s). Here, in this review article, we cover recent developments and applications of this technique in stem cells for research and clinical purposes and discuss different CRISPR/Cas technologies for knock-out, knock-in, activation, or inhibition of gene expression. Additionally, a comparison of several deliveries and off-target detecting strategies is discussed.

A novel technique for large-fragment knock-in animal production without ex vivo handling of zygotes

CRISPR/Cas-based genome editing has dramatically improved genetic modification technology. In situ electroporation called genome editing via oviductal nucleic acid delivery (GONAD), which eliminates the need for ex vivo embryo handling, is technically the simplest method for gene transfer and can be performed in laboratories without developmental engineering expertise including micromanipulation techniques. However, the use of this method remains challenging in the case of large-fragment knock-in, such as gene expression cassettes. Adeno-associated viruses (AAV) act as donor DNA for homologous recombination in infected cells, including rodent embryos. In this study, we demonstrated simultaneous electroporation of AAV donors and CRISPR/Cas9 components into embryos to create knock-in animals, and successfully generated knock-in rats carrying a gene cassette with a length of 3.0 kb using a small number of animals and in situ electroporation. These findings indicate that this technique is an efficient high-throughput strategy for producing genetically modified rodents and may be applicable to other animal species.

Strategies for generation of mice via CRISPR/HDR-mediated knock-in

CRISPR/Cas9 framework is generally used to generate genetically modified mouse models. The clustered regularly interspaced short palindromic repeat gene editing technique, can efficiently generate knock-outs using the non-homologous end-joining repair pathway. Small knock-ins also work precisely using a repair template with help of homology-directed-repair (HDR) mechanism. However, when the fragment size is larger than 4-5 kb, the knock-in tends to be error prone and the efficiency decreases. Certain types of modifications, in particular insertions of very large DNA fragments (10-100 kb) or entire gene replacements, are still difficult. The HDR process needs further streamlining and improvement. Here in this review, we describe methods to enhance the efficiency of the knock-in through checking each step from the guide design to the microinjection and choice of the oocyte donors. This helps in understanding the parameters that can be modified to get improved knock-in efficiency via CRISPR targeting.

CRISMERE Chromosome Engineering in Mouse and Rat

CRISPR/Cas9 technology is a versatile tool for engineering biology that has dramatically transformed our ability to manipulate genomes. In this protocol, we use its capacity to generate two double-strand breaks simultaneously, at precise positions in the genome, to generate mouse or rat lines with deletion, inversion, and duplication of a specific genomic segment. The technic is called CRISMERE for CRISpr-MEdiated REarrangement. This protocol describes the different steps to generate and validate the different chromosomal rearrangements that can be obtained with the technology. These new genetic configurations can be useful to model rare diseases with copy number variation, understand the genomic organization, or provide genetic tools (like balancer chromosome) to keep lethal mutations.

Protein structure determination in human cells by in-cell NMR and a reporter system to optimize protein delivery or transexpression

Most experimental methods for structural biology proceed in vitro and therefore the contribution of the intracellular environment on protein structure and dynamics is absent. Studying proteins at atomic resolution in living mammalian cells has been elusive due to the lack of methodologies. In-cell nuclear magnetic resonance spectroscopy (in-cell NMR) is an emerging technique with the power to do so. Here, we improved current methods of in-cell NMR by the development of a reporter system that allows monitoring the delivery of exogenous proteins into mammalian cells, a process that we called here "transexpression". The reporter system was used to develop an efficient protocol for in-cell NMR which enables spectral acquisition with higher quality for both disordered and folded proteins. With this method, the 3D atomic resolution structure of the model protein GB1 in human cells was determined with a backbone root-mean-square deviation (RMSD) of 1.1 Å.

High-content CRISPR screening in tumor immunology

CRISPR screening is a powerful tool that links specific genetic alterations to corresponding phenotypes, thus allowing for high-throughput identification of novel gene functions. Pooled CRISPR screens have enabled discovery of innate and adaptive immune response regulators in the setting of viral infection and cancer. Emerging methods couple pooled CRISPR screens with parallel high-content readouts at the transcriptomic, epigenetic, proteomic, and optical levels. These approaches are illuminating cancer immune evasion mechanisms as well as nominating novel targets that augment T cell activation, increase T cell infiltration into tumors, and promote enhanced T cell cytotoxicity. This review details recent methodological advances in high-content CRISPR screens and highlights the impact this technology is having on tumor immunology.

Delivering the CRISPR/Cas9 system for engineering gene therapies: Recent cargo and delivery approaches for clinical translation

Clustered Regularly Interspaced Short Palindromic Repeats associated protein 9 (CRISPR/Cas9) has transformed our ability to edit the human genome selectively. This technology has quickly become the most standardized and reproducible gene editing tool available. Catalyzing rapid advances in biomedical research and genetic engineering, the CRISPR/Cas9 system offers great potential to provide diagnostic and therapeutic options for the prevention and treatment of currently incurable single-gene and more complex human diseases. However, significant barriers to the clinical application of CRISPR/Cas9 remain. While in vitro, ex vivo, and in vivo gene editing has been demonstrated extensively in a laboratory setting, the translation to clinical studies is currently limited by shortfalls in the precision, scalability, and efficiency of delivering CRISPR/Cas9-associated reagents to their intended therapeutic targets. To overcome these challenges, recent advancements manipulate both the delivery cargo and vehicles used to transport CRISPR/Cas9 reagents. With the choice of cargo informing the delivery vehicle, both must be optimized for precision and efficiency. This review aims to summarize current bioengineering approaches to applying CRISPR/Cas9 gene editing tools towards the development of emerging cellular therapeutics, focusing on its two main engineerable components: the delivery vehicle and the gene editing cargo it carries. The contemporary barriers to biomedical applications are discussed within the context of key considerations to be made in the optimization of CRISPR/Cas9 for widespread clinical translation.

CRISPR/Cas9 system: a reliable and facile genome editing tool in modern biology

Genome engineering has always been a versatile technique in biological research and medicine, with several applications. In the last several years, the discovery of Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas9 technology has swept the scientific community and revolutionised the speed of modern biology, heralding a new era of disease detection and rapid biotechnology discoveries. It enables successful gene editing by producing targeted double-strand breaks in virtually any organism or cell type. So, this review presents a comprehensive knowledge about the mechanism and structure of Cas9-mediated RNA-guided DNA targeting and cleavage. In addition, genome editing via CRISPR-Cas9 technology in various animals which are being used as models in scientific research including Non-Human Primates Pigs, Dogs, Zebra, fish and Drosophila has been discussed in this review. This review also aims to understand the applications, serious concerns and future perspective of CRISPR/Cas9-mediated genome editing.

Multidrug-Resistant Microbial Therapy Using Antimicrobial Peptides and the CRISPR/Cas9 System

The emergence and spread of multidrug-resistant microbes become a serious threat to animal and human health globally because of their less responsiveness to conventional antimicrobial therapy. Multidrug-resistant microbial infection poses higher morbidity and mortality rate with significant economic losses. Currently, antimicrobial peptides and the CRISPR/Cas9 system are explored as alternative therapy to circumvent the challenges of multidrug-resistant organisms. Antimicrobial peptides are small molecular weight, cationic peptides extracted from all living organisms. It is a promising drug candidate for the treatment of multidrug-resistant microbes by direct microbial killing or indirectly modulating the innate immune system. The CRISPR/Cas9 system is another novel antimicrobial alternative used to manage multidrug-resistant microbial infection. It is a versatile gene-editing tool that uses engineered single guide RNA for targeted gene recognition and the Cas9 enzyme for the destruction of target nucleic acids. Both the CRISPR/Cas9 system and antimicrobial peptides were used to successfully treat nosocomial infections caused by ESKAPE pathogens, which developed resistance to various antimicrobials. Despite, their valuable roles in multidrug-resistant microbial treatments, both the antimicrobial peptides and the CRISPR/Cas systems have various limitations like toxicity, instability, and incurring high manufacturing costs. Thus, this review paper gives detailed explanations of the roles of the CRISPR/Cas9 system and antimicrobial peptides in circumventing the challenges of multidrug-resistant microbial infections, its limitation and prospects in clinical applications.

Progress of delivery methods for CRISPR-Cas9

INTRODUCTION

Gene therapy is becoming increasingly common in clinical practice, giving hope for the correction of a wide range of human diseases and defects. The CRISPR/Cas9 system, consisting of the Cas9 nuclease and single-guide RNA (sgRNA), has revolutionized the field of gene editing. However, efficiently delivering the CRISPR-Cas9 to the target organ or cell remains a significant challenge. In recent years, with rapid advances in nanoscience, materials science, and medicine, researchers have developed various technologies that can deliver CRISPR-Cas9 in different forms for in vitro and in vivo gene editing. Here, we review the development of the CRISPR-Cas9 and describe the delivery forms and the vectors that have emerged in CRISPR-Cas9 delivery, summarizing the key barriers and the promising strategies that vectors currently face in delivering the CRISPR-Cas9.

AREAS COVERED

With the rapid development of CRISPR-Cas9, delivery methods are becoming increasingly important in the in vivo delivery of CRISPR-Cas9.

EXPERT OPINION

CRISPR-Cas9 is becoming increasingly common in clinical trials. However, the complex nuclease and protease environment is a tremendous challenge for in vivo clinical applications. Therefore, the development of delivery methods is highly likely to take the application of CRISPR-Cas9 technology to another level.

Highly reliable creation of floxed alleles by electroporating single-cell embryos

BACKGROUND

Floxed (flanked by loxP) alleles are a crucial portion of conditional knockout mouse models. However, an efficient and reliable strategy to flox genomic regions of any desired size is still lacking.

RESULTS

Here, we demonstrate that the method combining electroporation of fertilized eggs with gRNA/Cas9 complexes and single-stranded oligodeoxynucleotides (ssODNs), assessing phasing of loxP insertions in founders using an in vitro Cre assay and an optional, highly specific and efficient second-round targeting ensures the generation of floxed F1 animals in roughly five months for a wide range of sequence lengths (448 bp to 160 kb reported here).

CONCLUSIONS

Floxed alleles can be reliably obtained in a predictable timeline using the improved method of electroporation of two gRNA/Cas9 ribonucleoprotein particles (RNPs) and two ssODNs.

CRISPR/Cas9 ribonucleoprotein-mediated genome and epigenome editing in mammalian cells

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein (Cas) system has revolutionized the ability to edit the mammalian genome, providing a platform for the correction of pathogenic mutations and further investigation into gene function. CRISPR reagents can be delivered into the cell as DNA, RNA, or pre-formed ribonucleoproteins (RNPs). RNPs offer numerous advantages over other delivery approaches due to their ability to rapidly target genomic sites and quickly degrade thereafter. Here, we review the production steps and delivery methods for Cas9 RNPs. Additionally, we discuss how RNPs enhance genome and epigenome editing efficiencies, reduce off-target editing activity, and minimize cellular toxicity in clinically relevant mammalian cell types. We include details on a broad range of editing approaches, including novel base and prime editing techniques. Finally, we summarize key challenges for the use of RNPs, and propose future perspectives on the field.

Delivery of CRISPR-Cas9 system for screening and editing RNA binding proteins in cancer

RNA-binding proteins (RBPs) play an important role in RNA metabolism, regulating the stability, localization, and functional dynamics of RNAs. Alternation in the RBP-RNA network has profound implications in cellular physiology, and is related to the development and spread of cancer in certain cases. To regulate the expression of specific genes and their biological activities, various strategies have been applied to target RBPs for cancer treatments, including small-molecule inhibitors, small-interfering RNA, peptides, and aptamers. Recently, the deployment of the CRISPR-Cas9 technology has provided a new platform for RBP screening and regulation. This review summarizes the delivery systems of the CRISPR-Cas9 system and their role in RBP-based cancer therapeutics, including identification of novel RBPs and regulation of cancer-associated RBPs. The efficient delivery of the CRISPR-Cas9 system is important to the profound understanding and clinical transition of RBPs as cancer therapeutic targets.

CRISPR-Cas9 effectors facilitate generation of single-sex litters and sex-specific phenotypes

Animals are essential genetic tools in scientific research and global resources in agriculture. In both arenas, a single sex is often required in surplus. The ethical and financial burden of producing and culling animals of the undesired sex is considerable. Using the mouse as a model, we develop a synthetic lethal, bicomponent CRISPR-Cas9 strategy that produces male- or female-only litters with one hundred percent efficiency. Strikingly, we observe a degree of litter size compensation relative to control matings, indicating that our system has the potential to increase the yield of the desired sex in comparison to standard breeding designs. The bicomponent system can also be repurposed to generate postnatal sex-specific phenotypes. Our approach, harnessing the technological applications of CRISPR-Cas9, may be applicable to other vertebrate species, and provides strides towards ethical improvements for laboratory research and agriculture.

Applications and challenges of CRISPR-Cas gene-editing to disease treatment in clinics

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated systems (Cas) are efficient tools for targeting specific genes for laboratory research, agricultural engineering, biotechnology, and human disease treatment. Cas9, by far the most extensively used gene-editing nuclease, has shown great promise for the treatment of hereditary diseases, viral infection, cancers, and so on. Recent reports have revealed that some other types of CRISPR-Cas systems may also have surprising potential to join the fray as gene-editing tools for various applications. Despite the rapid progress in basic research and clinical tests, some underlying problems present continuous, significant challenges, such as editing efficiency, relative difficulty in delivery, off-target effects, immunogenicity, etc. This article summarizes the applications of CRISPR-Cas from bench to bedside and highlights the current obstacles that may limit the usage of CRISPR-Cas systems as gene-editing toolkits in precision medicine and offer some viewpoints that may help to tackle these challenges and facilitate technical development. CRISPR-Cas systems, as a powerful gene-editing approach, will offer great hopes in clinical treatments for many individuals with currently incurable diseases.

Direct protein delivery into intact plant cells using polyhistidine peptides

Polyhistidine peptides (PHPs), sequences comprising only histidine residues (>His8), are effective cell-penetrating peptides for plant cells. Using PHP-fusion proteins, we aimed to deliver proteins into cultured plant cells from Nicotiana tabacum, Oryza sativa, and Cryptomeria japonica. Co-cultivation of cultured cells with fusion proteins combining maltose-binding protein (MBP), red fluorescent protein (RFP), and various PHPs (MBP-RFP-His8-His20) in one polypeptide showed the cellular uptake of fusion proteins in all plant cell lines. Maximum intracellular fluorescence was shown in MBP-RFP-His20. Further, adenylate cyclase (CyaA), a synthase of cyclic adenosine monophosphate (cAMP) activated by cytosolic calmodulin, was used as a reporter for protein delivery in living cells. A fusion protein combining MBP, RFP, CyaA, and His20 (MBP-RFP-CyaA-His20) was delivered into plant cells and increased intracellular fluorescence and cAMP production in all cell lines. The present study demonstrates that PHPs are effective carriers of proteins into the intracellular space of various cultured plant cells.

An efficient i-GONAD method for creating and maintaining lethal mutant mice using an inversion balancer identified from the C3H/HeJJcl strain

As the efficiency of the clustered regularly interspaced short palindromic repeats/Cas system is extremely high, creation and maintenance of homozygous lethal mutants are often difficult. Here, we present an efficient in vivo electroporation method called improved genome editing via oviductal nucleic acid delivery (i-GONAD), wherein one of two alleles in the lethal gene was selectively edited in the presence of a non-targeted B6.C3H-In(6)1J inversion identified from the C3H/HeJJcl strain. This method did not require isolation, culture, transfer, or other in vitro handling of mouse embryos. The edited lethal genes were stably maintained in heterozygotes, as recombination is strongly suppressed within this inversion interval. Using this strategy, we successfully generated the first Tprkb null knockout strain with an embryonic lethal mutation and showed that B6.C3H-In(6)1J can efficiently suppress recombination. As B6.C3H-In(6)1J was tagged with a gene encoding the visible coat color marker, Mitf, the Tprkb mutation could be visually recognized. We listed the stock balancer strains currently available as public bioresources to create these lethal gene knockouts. This method will allow for more efficient experiments for further analysis of lethal mutants.

Therapeutic Genome Editing and In Vivo Delivery

Improvements in the understanding of human genetics and its roles in disease development and prevention have led to an increased interest in therapeutic genome editing via the use of engineered nucleases. Various approaches have been explored in the past focusing on the development of an effective and safe system for sequence-specific editing. Compared to earlier nucleases such as zinc finger nuclease and transcription activator-like effector nuclease, the relatively low cost and ease of producing clustered regularly interspaced short palindromic repeats associated protein 9 (CRISPR/Cas9) systems have made therapeutic genome editing significantly more feasible. CRISPR/Cas9 genome editing has shown great potential to correct genetic mutations implicated in monogenic diseases and to eradicate latent or chronic viral infections in preclinical studies. Several CRISPR/Cas9-based therapeutics have reached the clinical stage, including treatments for inherited red blood cell disorders and Leber Congenital Amaurosis 10, as well as CRISPR/Cas9-edited T cells designed to target and destroy cancer cells. Further advances in therapeutic genome editing will rely on a safe and more efficient method of in vivo CRISPR/Cas9 delivery and improved efficiency of homology-directed repair for site-specific gene insertion or replacement. While other reviews have focused on one or two aspects of CRISPR/Cas9 genome editing, this review aims to provide a summary of the mechanisms of genome editing, the reasons for the emerging interest in CRISPR/Cas9 compared to other engineered nucleases, the current progress in developing CRISPR/Cas9 delivery systems, and the current preclinical and clinical applications of CRISPR/Cas9 genome editing.