Evolution of Transgenic Technology: From Random Transgenesis to Precise Genome Editing

New techniques in molecular biology help us for better understanding of biological processes. As biologists we resort to powerful approaches for efficient gene transfer which would enable us to study alterations in gene activity, in vivo. Although embryonic stem cell mediated transgenesis enabled targeted gene transfer through homologous recombination, the efficiency of such techniques remains very low. The recent emergence of genome editing technology provides a feasible approach to introduce a variety of precise heritable modifications into the mammalian genome. In this chapter, we review conventional transgenic methods, the transgene design and the structure and function of different genome editors. Further, we provide updates on the diverse applications of genome editing technology pertaining to agriculture and biomedical research, and lastly discusses perspectives. Though the pronuclear injection method and embryonic stem cell technique were quite successful in generating transgenic mice, they remained highly challenging for livestock transgenesis. The discovery of the somatic cell nuclear transfer (SCNT) technique led to fruitful development of transgenic farm animals, but suffers from low in utero survival rate. With the advent of genome editors, animal transgenesis gained new heights, a variety of precise modifications including multiplex gene edits and single base change could be performed with an unprecedented ease. Among all gene editors, CRISPR/Cas system has become the method of choice due to simplicity of construction, low cost and multiple gene editing ability. The diverse applications of gene editing technologies for generation of transgenic animal includes enhancing important production traits, improving disease resistance and developing animal bioreactors and biomedical models. Nevertheless, there are many hurdles yet to be resolved, development of improved genome editing tools would necessarily ensure bright application in the field of animal transgenesis.