SNP Introgression by Genome Editing Technology in Pigs

Man has been breeding animals for millennia, initially on behavioural characteristics, then visual traits and very recently by selection based on genetic tools. With the unrelenting progress of genomic resources the animal breeder can now utilises sequence variation across the entire genome. Selective breeding exploits the variation that exists within a population of animals, capturing beneficial genotypes to deliver genetic improvement to that population. This process often requires multiple mating regimes and is therefore time consuming. It also relies on the presence or spontaneous appearance of the desired genetic variation in the target breeding gene pool. If the genetic variation does not exist in a given breeding population then it cannot be selected. Neither has it been possible to exploit potentially beneficial variation from other species or other genera because of mating barriers, while expanding the frequency of rare alleles in a population is challenging. The recent development of genome editing technology now enables the use of genetic variation that is not present within a given breeding population. Genome editors are engineered nucleases that direct double-strand breaks to specific target DNA sequences. These tools enable sequence insertions/deletions at the target locus or the introduction of new alleles. Thus, we can now achieve in a single-generation, introgression of a desired haplotype, even from another species, without introducing other unwanted DNA sequences. This opens unprecedented opportunities for agriculture.