CRISPR-mediated biocontainment

Nature Methods, 2014

A key obstacle to creating sophisticated genetic circuits has been the lack of scalable device libraries. Here we present a modular transcriptional repression architecture based on clustered regularly interspaced palindromic repeats (CRISPR) system and examine approaches for regulated expression of guide RNAs in human cells. Subsequently we demonstrate that CRISPR regulatory devices can be layered to create functional cascaded circuits, which provide a valuable toolbox for engineering purposes. Engineered biological circuits provide insights into the underlying biology of living cells and offer potential solutions to a range of medical and industrial challenges 1, 2 . A prerequisite for efficient engineering of such sophisticated circuits is the availability of a library of regulatory devices that can be connected in various contexts to create new and

Biotechnology Reports, 2022

The CRISPR-Cas systems have offered a flexible, easy-to-use platform to precisely modify and control the genomes of organisms in various fields, ranging from agricultural biotechnology to therapeutics. This system is extensively used in the study of infectious, progressive, and life-threatening genetic diseases for the improvement of quality and quantity of major crops and in the development of sustainable methods for the generation of biofuels. As CRISPR-Cas technology continues to evolve, it is becoming more controllable and precise with the addition of molecular regulators, which will provide benefits for everyone and save many lives. Studies on the constant growth of CRISPR technology are important due to its rapid development. In this paper, we present the current applications and progress of CRISPR-Cas genome editing systems in several fields of research, we further highlight the applications of anti-CRISPR molecules to regulate CRISPR-Cas gene editing systems, and we discuss ethical considerations in CRISPR-Cas applications.

Genome biology, 2018

While CRISPR-Cas systems hold tremendous potential for engineering the human genome, it is unclear how well each system performs against one another in both non-homologous end joining (NHEJ)-mediated and homology-directed repair (HDR)-mediated genome editing. We systematically compare five different CRISPR-Cas systems in human cells by targeting 90 sites in genes with varying expression levels. For a fair comparison, we select sites that are either perfectly matched or have overlapping seed regions for Cas9 and Cpf1. Besides observing a trade-off between cleavage efficiency and target specificity for these natural endonucleases, we find that the editing activities of the smaller Cas9 enzymes from Staphylococcus aureus (SaCas9) and Neisseria meningitidis (NmCas9) are less affected by gene expression than the other larger Cas proteins. Notably, the Cpf1 nucleases from Acidaminococcus sp. BV3L6 and Lachnospiraceae bacterium ND2006 (AsCpf1 and LbCpf1, respectively) are able to perform p...

Molecular Therapy - Nucleic Acids, 2017

Trends in biotechnology, 2018

Clustered regularly interspaced short palindromic repeat-CRISPR-associated protein (CRISPR-Cas) systems, found in nature as microbial adaptive immune systems, have been repurposed into an important tool in biological engineering and genome editing, providing a programmable platform for precision gene targeting. These tools have immense promise as therapeutics that could potentially correct disease-causing mutations. However, CRISPR-Cas gene editing components must be transported directly to the nucleus of targeted cells to exert a therapeutic effect. Thus, efficient methods of delivery will be critical to the success of therapeutic genome editing applications. Here, we review current strategies available for in vivo delivery of CRISPR-Cas gene editing components and outline challenges that need to be addressed before this powerful tool can be deployed in the clinic.

In the last few decades, genomic manipulation has made significant progress as a result of the development of recombinant DNA technologies; however, more often than not, these techniques have been costly and labor intensive. In contrast, recently developed next-generation sequencing (NGS) technologies have provided a cheaper, faster, and easier process to study genomics. In particular, an NGS technique emerged from bacterial CRISPR-associated protein-9 nuclease (Cas9) as a revolutionary method to modify, regulate, or mark specific genomic sequences on virtually any organism. A later adaptation of this bacterial defense mechanism that successfully and permanently edits dysfunctional genes and corrects missing proteins has resulted in a new era for disease genetic engineering. Clinical trials using this technique are already being performed, and the applicability of CRISPR-Cas9 techniques is actively being investigated using in vivo studies. However, the concept of genome correction poses great concerns from a regulatory perspective, especially in terms of security, so principles for the regulation of these methodologies are being established. We delved into CRISPR-Cas9 from its natural and ortholog origins to its engineered variants and behaviors to present its notable and diverse applications in the fields of biotechnology and human therapeutics.

BioTechniques, 2014

The prokaryotic type II CRISPR/Cas9 system has been adapted to perform targeted genome editing in cells and model organisms. Here, we describe targeted gene deletion and replacement in human cells via the CRISPR/Cas9 system using two guide RNAs. The system effectively generated targeted deletions of varied length, regardless of the transcriptional status of the target gene. It is notable that targeted gene deletions generated via CRISPR/Cas9 and two guide RNAs resulted in the formation of correct junctions at high efficiency. Moreover, in the presence of a homology repair donor, the CRISPR/Cas9 system could guide precise gene replacement. Our results illustrate that the CRISPR/Cas9 system can be used to precisely and effectively generate targeted deletions or gene replacement in human cells, which will facilitate characterization of functional domains in protein-coding genes as well as noncoding regulatory sequences in animal genomes.

The ability to engineer biological systems and organisms holds enormous potential for applications across basic science, medicine and biotechnology. Programmable sequence-specific endonucleases that facilitate precise editing of endogenous genomic loci are now enabling systematic interrogation of genetic elements and causal genetic variations 1,2 in a broad range of species, including those that have not previously been genetically tractable 3-6. A number of genome editing technologies have emerged in recent years, including zinc-finger nucleases (ZFNs) 7-10 , transcription activator-like effector nucleases (TALENs) 10-17 and the RNA-guided CRISPR-Cas nuclease system 18-25. The first two technologies use a strategy of tethering endonuclease catalytic domains to modular DNA-binding proteins for inducing targeted DNA double-stranded breaks (DSBs) at specific genomic loci. By contrast, Cas9 is a nuclease guided by small RNAs through Watson-Crick base pairing with target DNA 26-28 (Fig. 1), representing a system that is markedly easier to design, highly specific, efficient and well-suited for highthroughput and multiplexed gene editing for a variety of cell types and organisms. Precise genome editing using engineered nucleases Similarly to ZFNs and TALENs, Cas9 promotes genome editing by stimulating a DSB at a target genomic locus 29,30. Upon cleavage by Cas9, the target locus typically undergoes one of two major pathways for DNA damage repair (Fig. 2): the error-prone NHEJ or the high-fidelity HDR pathway, both of which can be used to achieve a desired editing outcome. In the absence of a repair template, DSBs are re-ligated through the NHEJ process, which leaves scars in the form of insertion/deletion (indel) mutations. NHEJ can be harnessed to mediate gene knockouts, as indels occurring within a coding exon can lead to frameshift mutations and premature stop codons 31. Multiple DSBs can additionally be exploited to mediate larger deletions in the genome 22,32. HDR is an alternative major DNA repair pathway. Although HDR typically occurs at lower and substantially more variable frequencies than NHEJ, it can be leveraged to generate precise, defined modifications at a target locus in the presence of an exogenously introduced repair template. The repair template can either be in the form of conventional double-stranded DNA targeting constructs with homology arms flanking the insertion sequence, or single-stranded DNA oligonucleotides (ssODNs). The latter provides an effective and simple method for making small edits in the genome, such as the introduction of singlenucleotide mutations for probing causal genetic variations 32. Unlike NHEJ, HDR is generally active only in dividing cells, and its efficiency can vary widely depending on the cell type and state, as well as the genomic locus and repair template 33. Cas9: an RNA-guided nuclease for genome editing CRISPR-Cas is a microbial adaptive immune system that uses RNA-guided nucleases to cleave foreign genetic elements 18-21,26. Three types (I-III) of CRISPR systems have been identified across a wide range of bacterial and archaeal hosts, wherein each system comprises a cluster of CRISPR-associated (Cas) genes, noncoding RNAs and a distinctive array of repetitive elements (direct repeats). These repeats are interspaced by short variable sequences 20 derived from exogenous DNA targets known as protospacers, and together they constitute the CRISPR RNA (crRNA) array. Within the DNA target, each protospacer is always associated with a protospacer adjacent motif (PAM), which can vary depending on the specific CRISPR system 34-36. The Type II CRISPR system is one of the best characterized 26-28,37,38 , consisting of the nuclease Cas9, the crRNA array that encodes the guide RNAs and a required auxiliary trans-activating crRNA (tracrRNA) that facilitates the processing of the crRNA array into discrete units 26,28. Each crRNA unit then contains a 20-nt guide sequence and a partial direct repeat, where the former directs Cas9 to a 20-bp DNA target via Watson-Crick base pairing (Fig. 1). In the CRISPR-Cas system derived from Streptococcus pyogenes (which is the system used in this protocol), the target DNA must immediately precede a 5′-NGG PAM 27 , whereas

Bioengineered

In recent years there has been great progress with the implementation and utilization of Clustered Regularly Interspaced Palindromic Repeats (CRISPR) and CRISPR-associated protein (Cas) systems in the world of genetic engineering. Many forms of CRISPR-Cas9 have been developed as genome editing tools and techniques and, most recently, several non-genome editing CRISPR-Cas systems have emerged. Most of the CRISPR-Cas systems have been classified as either Class I or Class II and are further divided among several subtypes within each class. Research teams and companies are currently in dispute over patents for these CRISPR-Cas systems as numerous powerful applications are concurrently under development. This mini review summarizes the appearance of CRISPR-Cas systems with a focus on the predominant CRISPR-Cas9 system as well as the classifications and subtypes for CRISPR-Cas. Non-genome editing uses of CRISPR-Cas are also highlighted and a brief overview of the commercialization of CRISPR is provided.