Genome Editing

Targeted editing of the genomes of living organisms not only permits investigations into the understanding of the fundamental basis of biological systems but also allows to improve productively and quality of crops. This includes the creation of plants with valuable compositional properties and with traits that confer resistance to various biotic and abiotic stresses. Recently, several novel genome editing systems have been developed, which include zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALNEs), and clustered regularly interspersed short palindromic repeats/Cas9 (CRISPER/Cas9). These exciting new methods have proved themselves as effective and reliable tools for the genetic improvement of plants. The genome editing systems can also be used to exploit the genetic diversity present in the semi-domesticated and wild relatives of the cultivated crops by targeting homologous domesticated genes through allele-mining. In this chapter various tools available for gene editing, their merits, and demerits have been discussed.

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Venera S. Kamburova ◽  
Elena V. Nikitina ◽  
Shukhrat E. Shermatov ◽  
Zabardast T. Buriev ◽  
Siva P. Kumpatla ◽  
...  

The emergence of genome manipulation methods promises a real revolution in biotechnology and genetic engineering. Targeted editing of the genomes of living organisms not only permits investigations into the understanding of the fundamental basis of biological systems but also allows addressing a wide range of goals towards improving productivity and quality of crops. This includes the creation of plants with valuable compositional properties and with traits that confer resistance to various biotic and abiotic stresses. During the past few years, several novel genome editing systems have been developed; these include zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats/Cas9 (CRISPR/Cas9). These exciting new methods, briefly reviewed herein, have proved themselves as effective and reliable tools for the genetic improvement of plants.


Traditional plant breeding depends on spontaneous and induced mutations available in the crop plants. Such mutations are rare and occur randomly. By contrast, molecular breeding and genome editing are advanced breeding techniques that can enhance the selection process and produce precisely targeted modifications in any crop. Identification of molecular markers, based on SSRs and SNPs, and the availability of high-throughput (HTP) genotyping platforms have accelerated the process of generating dense genetic linkage maps and thereby enhanced application of marker-assisted breeding for crop improvement. Advanced molecular biology techniques that facilitate precise, efficient, and targeted modifications at genomic loci are termed as “genome editing.” The genome editing tools include “zinc-finger nucleases (ZNFs),” “transcription activator-like effector nucleases (TALENs),” oligonucleotide-directed mutagenesis (ODM), and “clustered regularly interspersed short palindromic repeats (CRISPER/Cas) system,” which can be used for targeted gene editing. Concepts of molecular plant breeding and genome editing systems are presented in this chapter.


2014 ◽  
Vol 462 (1) ◽  
pp. 15-24 ◽  
Author(s):  
David A. Wright ◽  
Ting Li ◽  
Bing Yang ◽  
Martin H. Spalding

Genome editing is the practice of making predetermined and precise changes to a genome by controlling the location of DNA DSBs (double-strand breaks) and manipulating the cell's repair mechanisms. This technology results from harnessing natural processes that have taken decades and multiple lines of inquiry to understand. Through many false starts and iterative technology advances, the goal of genome editing is just now falling under the control of human hands as a routine and broadly applicable method. The present review attempts to define the technique and capture the discovery process while following its evolution from meganucleases and zinc finger nucleases to the current state of the art: TALEN (transcription-activator-like effector nuclease) technology. We also discuss factors that influence success, technical challenges and future prospects of this quickly evolving area of study and application.


Author(s):  
Silas Obukosia ◽  
Olalekan Akinbo ◽  
Woldeyesus Sinebo ◽  
Moussa Savadogo ◽  
Samuel Timpo ◽  
...  

A new set of breeding techniques, referred to as New Breeding Techniques developed in the last two decades have potential for enhancing improved productivity in crop and animal breeding globally. These include site directed nucleases based genomic editing procedures-CRISPR and Cas associated proteins, Zinc Finger Nucleases, Meganucleases/Homing Endonucleases and Transcription- Activator Like-Effector Nucleases for genome editing and other technologies including- Oligonucleotide-Directed Mutagenesis, Cisgenesis and intragenesis, RNA-Dependent DNA methylation; Transgrafting, Agroinfiltration, Reverse breeding. There are ongoing global debates on whether the processes of and products emerging from these technologies should be regulated as genetically modified organisms or approved as conventional products. Decisions on whether to regulate as GMOs are based both on understanding of the molecular basis of their development and if the GMO intermediate step was used. For example- cisgenesis, can be developed using Agrobacterium tumefaciens methods of transformation, a process used by GMO but if the selection is properly conducted the intermediate GMO elements will be eliminated and the final product will be identical to the conventionally developed crops. Others like Site Directed Nuclease 3 are regulated as GMOs in countries such as United State of America, Canada, European Union, Argentina, Australia. Progress in genome editing research, testing of genome edited bacterial blight resistant rice, development of Guidelines for regulating new breeding techniques or genome editing in Africa is also covered with special reference to South Africa, Kenya and Nigeria. Science- and evidence-based approach to regulation of new breeding techniques among regulators and policy makers should be strongly supported.


2018 ◽  
Vol 115 (38) ◽  
pp. 9351-9358 ◽  
Author(s):  
Robert M. Yarrington ◽  
Surbhi Verma ◽  
Shaina Schwartz ◽  
Jonathan K. Trautman ◽  
Dana Carroll

Genome editing with CRISPR-Cas nucleases has been applied successfully to a wide range of cells and organisms. There is, however, considerable variation in the efficiency of cleavage and outcomes at different genomic targets, even within the same cell type. Some of this variability is likely due to the inherent quality of the interaction between the guide RNA and the target sequence, but some may also reflect the relative accessibility of the target. We investigated the influence of chromatin structure, particularly the presence or absence of nucleosomes, on cleavage by the Streptococcus pyogenes Cas9 protein. At multiple target sequences in two promoters in the yeast genome, we find that Cas9 cleavage is strongly inhibited when the DNA target is within a nucleosome. This inhibition is relieved when nucleosomes are depleted. Remarkably, the same is not true of zinc-finger nucleases (ZFNs), which cleave equally well at nucleosome-occupied and nucleosome-depleted sites. These results have implications for the choice of specific targets for genome editing, both in research and in clinical and other practical applications.


Author(s):  
Yingzi Zhang ◽  
Mo Li

Viral infectious diseases are significant threats to the welfare of world populations. Besides the widespread acute viral infections (e.g., dengue fever) and chronic infections [e.g., those by the human immunodeficiency virus (HIV) and hepatitis B virus (HBV)], emerging viruses, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), pose great challenges to the world. Genome editing technologies, including clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) proteins, zinc-finger nucleases (ZFNs), and transcription activator-like effector nucleases (TALENs), have played essential roles in the study of new treatment for viral infectious diseases in cell lines, animal models, and clinical trials. Genome editing tools have been used to eliminate latent infections and provide resistance to new infections. Increasing evidence has shown that genome editing-based antiviral strategy is simple to design and can be quickly adapted to combat infections by a wide spectrum of viral pathogens, including the emerging coronaviruses. Here we review the development and applications of genome editing technologies for preventing or eliminating infections caused by HIV, HBV, HPV, HSV, and SARS-CoV-2, and discuss how the latest advances could enlighten further development of genome editing into a novel therapy for viral infectious diseases.


2020 ◽  
Vol 21 (16) ◽  
pp. 5665 ◽  
Author(s):  
Sunny Ahmar ◽  
Sumbul Saeed ◽  
Muhammad Hafeez Ullah Khan ◽  
Shahid Ullah Khan ◽  
Freddy Mora-Poblete ◽  
...  

Genome editing is a relevant, versatile, and preferred tool for crop improvement, as well as for functional genomics. In this review, we summarize the advances in gene-editing techniques, such as zinc-finger nucleases (ZFNs), transcription activator-like (TAL) effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR) associated with the Cas9 and Cpf1 proteins. These tools support great opportunities for the future development of plant science and rapid remodeling of crops. Furthermore, we discuss the brief history of each tool and provide their comparison and different applications. Among the various genome-editing tools, CRISPR has become the most popular; hence, it is discussed in the greatest detail. CRISPR has helped clarify the genomic structure and its role in plants: For example, the transcriptional control of Cas9 and Cpf1, genetic locus monitoring, the mechanism and control of promoter activity, and the alteration and detection of epigenetic behavior between single-nucleotide polymorphisms (SNPs) investigated based on genetic traits and related genome-wide studies. The present review describes how CRISPR/Cas9 systems can play a valuable role in the characterization of the genomic rearrangement and plant gene functions, as well as the improvement of the important traits of field crops with the greatest precision. In addition, the speed editing strategy of gene-family members was introduced to accelerate the applications of gene-editing systems to crop improvement. For this, the CRISPR technology has a valuable advantage that particularly holds the scientist’s mind, as it allows genome editing in multiple biological systems.


2019 ◽  
Vol 20 (15) ◽  
pp. 3719 ◽  
Author(s):  
Zahra Hajiahmadi ◽  
Ali Movahedi ◽  
Hui Wei ◽  
Dawei Li ◽  
Yasin Orooji ◽  
...  

The CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeat-associated protein 9) is a powerful genome-editing tool in animals, plants, and humans. This system has some advantages, such as a high on-target mutation rate (targeting efficiency), less cost, simplicity, and high-efficiency multiplex loci editing, over conventional genome editing tools, including meganucleases, transcription activator-like effector nucleases (TALENs), and zinc finger nucleases (ZFNs). One of the crucial shortcomings of this system is unwanted mutations at off-target sites. We summarize and discuss different approaches, such as dCas9 and Cas9 paired nickase, to decrease the off-target effects in plants. According to studies, the most effective method to reduce unintended mutations is the use of ligand-dependent ribozymes called aptazymes. The single guide RNA (sgRNA)/ligand-dependent aptazyme strategy has helped researchers avoid unwanted mutations in human cells and can be used in plants as an alternative method to dramatically decrease the frequency of off-target mutations. We hope our concept provides a new, simple, and fast gene transformation and genome-editing approach, with advantages including reduced time and energy consumption, the avoidance of unwanted mutations, increased frequency of on-target changes, and no need for external forces or expensive equipment.


2015 ◽  
Vol 27 (1) ◽  
pp. 108
Author(s):  
H. Matsunari ◽  
M. Watanabe ◽  
K. Nakano ◽  
A. Uchikura ◽  
Y. Asano ◽  
...  

Genome editing technologies have been used as a powerful strategy for the generation of genetically modified pigs. We previously developed genetically modified clone pigs with organogenesis-disabled phenotypes, as well as pigs exhibiting diseases with similar features to those of humans. Here, we report the production efficiency of various gene knockout cloned pigs from somatic cells that were genetically modified using zinc finger nucleases (ZFN) or transcription activator-like effector nucleases (TALEN). The ZFN- or TALEN-encoding mRNAs, which targeted 7 autosomal or X-linked genes, were introduced into porcine fetal fibroblast cells using electroporation. Clonal cell populations carrying induced mutations were selected after limiting dilution. The targeted portion of the genes was amplified using PCR, followed by sequencing and mutation analysis. Among the collected knockout cell colonies, cells showing good proliferation and morphology were selected and used for somatic cell nuclear transfer (SCNT). In vitro-matured oocytes were obtained from porcine cumulus-oocyte complexes cultured in NCSU23-based medium and were used to obtain recipient oocytes for SCNT after enucleation. SCNT was performed as reported previously (Matsunari et al. 2008). The cloned embryos were cultured for 7 days in porcine zygote medium (PZM)-5 to assess their developmental ability. Cloned embryos were transplanted into the oviduct or uterus of oestrus-synchronized recipient gilts to evaluate their competence to develop to fetuses or piglets. Cloned embryos reconstructed with 7 types of knockout cells showed equal development to blastocysts compared with those derived from the wild-type cells (54.5–83.3% v. 60.7%). Our data (Table 1) demonstrated that the reconstructed embryos derived from knockout cells could efficiently give rise to cloned offspring regardless of the type of genome editing methodology (i.e. ZFN or TALEN). Table 1.Production efficiency of gene knockout cloned pigs using genome editing This study was supported by JST, ERATO, the Nakauchi Stem Cell and Organ Regeneration Project, JST, CREST, Meiji University International Institute for Bio-Resource Research (MUIIBR), and JSPS KAKENHI Grant Number 26870630.


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