ISSN 0026-8933, Molecular Biology, 2014, Vol. 48, No. 3, pp. 305–318. © Pleiades Publishing, Inc., 2014. Original Russian Text © D.V. Glazkova, G.A. Shipulin, 2014, published in Molekulyarnaya Biologiya, 2014, Vol. 48, No. 3, pp. 355–370. 305 INTRODUCTION Construction of cells or organisms with targeted changes in individual genes or other elements of the genome makes it possible to solve many problems of basic science, biotechnology, and medicine. In 2007, the Nobel Prize was awarded “for the discoveries of principles for introducing specific gene modifications in mice by the use of embryonic stem cells”. The dis- covery allowed a method to be developed for con- structing mice with selectively inactivated (knockout) genes. The method opened a new epoch in mamma- lian genetics and provided a potent tool for studying the gene functions, but studies in the field were restricted to mouse as the only species for a long time. The possibility to manipulate the mouse genome, but not the genomes of other species, explains in part why mice are still most commonly used to model human hereditary disorders. Gene therapies for human hereditary disorders have been developed intensely over the past years. In early clinical studies, a functional copy of the defective gene was added to one of the chromosomes via ran- dom incorporation using viral vectors. The strategy had its drawbacks. On the one hand, exogenous DNA may distort the functions of neighbor genes to cause severe adverse effects. On the other hand, if the gene occurs in an inactive chromosome region, its expres- sion is low and the therapy is ineffective. An ideal solu- tion to the problem would be to correct the defective gene, i.e., necessary changes are made directly to the mutant gene region, preserving the physiological reg- ulation of gene expression from the endogenous pro- moter. Genome editing makes it possible to modify genes in any organisms or cells, to construct various model organisms, and to correct genes in hereditary disorders and opens many other opportunities. The gist is intro- ducing a break in a certain genomic DNA region so that its repair by cell mechanisms of homologous or nonhomologous recombination yields a desirable rearrangement. Recent achievements in research improved the efficiency and feasibility of the method, opening new prospects for constructing organisms with desirable properties in biotechnology and devel- oping gene therapies for hereditary disorders in medi- cine. Construction of TALE nucleases, which are the focus o ADVENT AND DEVELOPMENT OF GENE EDITING TECHNOLOGY The possibility to introduce targeted changes in the eukaryotic genome was first demonstrated in yeast TALE Nucleases As a New Tool for Genome Editing D. V. Glazkova and G. A. Shipulin Central Research Institute of Epidemiology, ??, Moscow, 111123 Russia; e-mail: glazkova@pcr.ru Received November 7, 2013 Accepted for publication December 23, 2013 Abstract—Introducing targeted changes in the genome of living cells or whole organisms makes it possible to solve many problems of basic science, biotechnology, and medicine. Target gene knockout in zygotes helps to study the functions of the gene in the corresponding organisms, while replacement of single nucleotide in DNA provides an opportunity to correct gene mutations and to treat hereditary disorders. Adding a gene into a proper genome region can be used to construct producer cells or organisms with certain properties. Such genomic manipulations are possible due to the technology known as genome editing. In this technology, a break is introduced into a certain chromosomal DNA region with an endonuclease recognizing a unique sequence, and DNA integrity is then restored by cell repair systems. Custom-designed endonucleases able to cleave a selected target sequence are necessary tools for genome editing. Programmable endonucleases of a new type were constructed on the basis of bacterial transcription activator-like (TAL) effectors (TALEs), marking an important step in the development of genome editing and promoting its broad application. The review considers the history of discovering TALEs and creating TALE nucleases and describes their advan- tages over zinc finger endonucleases, which were constructed earlier. A section focuses on the genetic modi- fications that can be performed using various genome editing techniques. DOI: 10.1134/S0026893314030054 Keywords: genome editing, TALE nuclease, zinc finger nuclease, homologous recombination, nonhomolo- gous end joining REVIEWS UDC 577.21 Abbreviations: TALE, TAL effector; ZF nuclease, zinc finger nuclease.