This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
In this week’s science page Alba Ledesma and Alison Van Eenennaam from the University of California, Davis take a look at how gene editing is being researched and regulated around the world!
Key Points:
- Gene editing (GnEd) can introduce useful genetic alterations in food animals
- Yield, reproduction, and disease resistance were the most commonly targeted traits
- CRISPR/Cas9 was by far the most prevalent GnEd system used to edit animal genomes
Gene editing (GnEd) involves using a site-directed nuclease to introduce a double-strand break (DSB) at a targeted location in the genome. Despite the fact that GnEd is a comparatively recent development compared to genetic engineering, food products from three GnEd animals have already reached the marketplace. We aimed to compile a comprehensive listing of peer-reviewed research on GnEd animals for food and agricultural applications globally.
Data was extracted from 212 peer-reviewed articles that described the production of at least one living animal employing GnEd technologies for agricultural purposes. Animal groups included in the reviewed papers were ruminants (cattle, sheep, goats, n=63); monogastrics (pigs and rabbits, n=60); avian (chicken, duck, quail, n=17); aquatic (many species, n=65), and insects (honeybee, silkworm, n=7). Yield (32%), followed by reproduction (21%) and disease resistance (17%) were the most commonly targeted traits. The most common GnEd system reported was CRISPR/Cas9, and the most frequent type of edit was the unguided insertion or deletion resulting from the repair of the targeted DSB leading to a knock-out (KO) mutation.
There are a number of groups working to develop pigs that are resistant to the porcine reproductive and respiratory syndrome (PRRS) virus. This virus severely affects the health and productivity of swine farms, causing a significant economic loss in the industry worldwide. The entrance of PRRS virus to the host cell is mediated by the scavenger receptor cysteine-rich protein domain 5 in receptor CD163. In twelve of the publications included in this literature review, the CD163 receptor was modified to prevent PRRS virus adhesion. In three of these publications, CD163 KO pigs had also a modification in another gene, such as MSTN or IGF-1, to increase pork yield, or ANPEP to increase resistance to transmissible gastroenteritis virus. The CRISPR/Cas9 system was the most utilized to induce alterations in the exon 7 sequence of CD163. Song et al. (2022) utilized a novel CBE to target CD163. Many laboratories are working on the production of hypoallergenic products derived from pigs for human medicine, including generating organs for transplantation to humans (xenotransplantation) that won’t be rejected. These biomedical applications of GnEd were not the focus of this review.
genome edited (GnEd) in animals. Current June 16, 2023.
Several countries, including Argentina, Australia, Brazil, Colombia and Japan, have adopted a regulatory policy that considers KO mutations introduced following GnEd DSB repair as akin to natural genetic variation, and therefore treat these GnEd animals analogously to those produced using conventional breeding. Figure 1 shows the countries with pending or existing policies around GnEd in animals, with those that have not started or are still developing their regulations indicated as unshaded.
The rate of publication in this field is accelerating rapidly. Ongoing advancements in both technology and application approaches have led to the refinement of gene-editing processes. Many countries are still developing their regulatory framework for GnEd animals. Given the importance of trade in both food and reproductive products derived from animals, the commercial future of GnEd animals will ultimately depend upon cooperation and alignment of regulatory approaches among potential trade partners.The full paper is available at: https://doi.org/10.1016/j.tvjl.2024.106142