Genome editing: current state and prospects for use in poultry (review)

To date, significant progress has been made in the poultry’s genetic modification. A sufficiently large number of methods and methodological approaches have been developed for the introduction of recombinant genes into bird cells. The efficiency of using these approaches for genetic modification of bird cells varies depending on the object of research, the selected target cells for the introduction of recombinant DNA and the method of their transformation. Blastoderm cells, primordial germ cells, spermatogonia, sperm cells, and oviduct cells can serve as target cells for gene modifications. Using retroviral, lentiviral and adenoviral vectors, electroporation and lipofection, genetic transformation of these target cells can be carried out. In general, three main strategies for creating a genetically modified bird can be distinguished: i) the introduction of genetic constructs directly into the embryo (J. Love et al., 1994; Z. Zhang et al., 2012) or into individual organs and tissues of adults (D.V. Beloglazov et al., 2015; S. Min et al., 2011), ii) transfection of target cells in vitro and their subsequent transplantation into the embryo or target organs (M.-C. van de Lavoir et al., 2006; B. Benesova et al., 2014), and iii) sperm transformation in vitro and insemination of females with transformed sperm (E. Harel-Markowitz et al., 2009). These approaches were used to develop methods for editing the avian cell genome. A number of papers have studied the possibility of modifying bird cells using various editing systems, in particular, ZFN (zinc finger nuclease), TALEN (transcription activator-like effector nucleases), and CRISPR/Cas9 (clustered regularly interspaced palindromic repeats). Promising areas of using this technology in poultry farming are the following: studying the genes functions (N. Véron et al., 2015), obtaining recombinant proteins in the egg white composition (I. Oishi et al., 2018), improving economically useful and productive qualities (J. Ahn et al., 2017), and increasing resistance to infectious diseases (A. Koslová et al., 2020; R. Hellmich et al., 2020). Chickens with knockout of genes of the heavy chain of immunoglobulin (B. Schusser et al., 2013; L. Dimitrov et al., 2016), ovomucin (I. Oishi et al., 2016), myostatin (G.-D. Kim et al., 2020), as well as an integrated human interferon beta gene (I. Oishi et al., 2018) were obtained using genome editing technology. Quail with knockout of myostatin genes (J. Lee et al., 2020) and melanophilin (J. Lee et al., 2019) were also obtained. A number of studies have shown the simplicity, safety and availability of using the CRISPR/Cas9 editing system for modifying the poultry genome. This allows us to consider this system as an effective tool for the creation and commercial use of breeds and lines of birds with improved qualities in the framework of the implementation of large-scale breeding programs aimed at improving the quality of the resulting poultry products.