Setsuro Tech succeeded in the production of genome-edited chicken using its proprietary genome-editing technology

Setsuro Tech Inc., which provides contract R&D service using genome editing, has succeeded in producing genome-edited chickens using its proprietary genome-editing technologies for the first time as a startup originated in a Japanese university.
This achievement will lead to the accelerated breeding of chicken and other poultry species and the development of high-value-added products. Setsuro Tech continues to be involved in further research and development work on chickens with the support of companies doing business in the poultry industry, such as Toyota Tsusho Corporation, one of the largest trading companies in Japan, and working towards the production of new genome-edited chicken breeds with traits favorable for consumers.

【Background Information】

Chickens represent highly beneficial and vital poultry and serve as an important source of meat and eggs. Moreover, in recent years, the value has been even higher because of the use of eggs in vaccine production and biopharmaceuticals. However, today’s poultry farming faces various challenges, such as new infectious diseases, climate change, and practices to improve animal welfare. Farmers awaited the development and implementation of new breeding technologies.
“Genome editing precision breeding,” which aims to develop new breeds through genome-editing technology, is one of the world’s hot topics, and the research employing genome editing is highly active. In mammals, such as mice and pigs, with the convenience of in vitro fertilization (IVF) technology, fertilized eggs/zygotes (1-cell stage) are used for manipulation and show high efficiency for ubiquitous genome editing.
However, unlike the case for mammals, IVF cannot be performed in chickens. fertilized chicken eggs/zygotes (1-cell stage) only exist inside the female body (oviduct); hence, they are difficult to manipulate. In addition, since embryos inside the laid eggs have already been divided into more than 20,000 cells, a high cell number makes them less efficient for genome editing. Thus, it is almost impossible to perform genome editing in chickens using fertilized eggs as materials without any special process.
Genome-edited chickens are produced via genome editing on primordial germ cells (PGCs), the “origin” of sperms and eggs, and transplanting the genome-edited PGCs into chicken embryos.
Generation of genome-edited chickens using PGCs require highly advanced technologies, including stable cell culture, genome editing, and the techniques for PGC transplantation. Because of this, successful cases of the generation of genome-edited chickens were limited, and only a few universities and public research institutes realized this.

【Research Overview】

Our research group, led by Prof. Tatsuya Takemoto and Dr. Yi-Chen Chen, derived PGCs from chicken embryos with an in vitro culture (Figure 1), and genome editing was performed in these cells to insert the fluorescent reporter gene mCherry into chicken cVasa gene locus for a specific expression in PGCs (cVasa-mCherry) (Figure 2).
Then, genome-edited PGCs were transplanted into recipient chicken embryos (Figure 3). The transplanted genome-edited PGCs moved inside the embryos and colonized in the gonads (testes/ovaries) of the recipient chickens. These chimeric chickens with PGC transplantation (F0 individuals) successfully reached sexual maturity and were crossed with wild-type chickens (Figure 4) to produce genome-edited chickens (F1 individuals) (Figures 5 and A).

Analysis of the genome-edited chickens revealed that as planned, a fluorescent protein gene was inserted into the cVasa locus. Red fluorescence was confirmed in the testes and ovaries, consistent with the expression of the cVasa gene (new characteristics are conferred to genome-edited chickens, Figure B). All the cells constituting these F1 chicken individuals were cVasa-mCherry heterozygous genotypes, and the new characteristics were maintained in the subsequent offspring.

【Production of genome-edited chickens with additional value to consumers】

Setsuro Tech is providing PAGEs, a contracted research and development service that uses genome-editing technology, which enables the flexible editing of genes of living organisms, aiding the development of novel breeds in the field of agriculture and livestock breeding in accordance with customer needs.
This research aims to establish a technology for producing genome-edited chickens. We used a fluorescent protein as a reporter to visualize the expression of the cVasa gene. Based on the results of this project, we will work on further joint development with Toyota Tsusho and other companies in the chicken business to generate new benefits for consumers, accelerate breeding, and effectively create new breeds with higher-value traits.

【Explanation of terms】

1）primordial germ cell (PGC): A progenitor cell type capable of giving rise to sperm and eggs.
2）cVasa gene: A gene that is specifically expressed in the germ cells of chicken.
3）mCherry: A protein derived from sea anemones that emits red fluorescence and used as a reporter gene
4）recipient chickens： Chickens that receive the transplantation of PGCs.

About Setsuro Tech Inc.

Setsuro Tech Inc. is a startup from Tokushima University, which was founded in 2017 based on the technology and know-how cultivated at the Tokushima University. In 2015, Tatsuya Takemoto (Representative Director, Chairman, and CTO) of the Tokushima University and others developed “a method that can easily and efficiently produce genome-edited mice” (Japanese Patent No. 6980218).
Shun Sawatsuhashi (Executive CSO) of the Tokushima University developed the VIKING method, which realizes highly-efficient genome editing in cultured cells (Japanese patent No. 6956995). Furthermore, we have developed our own novel genome editing factor ST8 (Japanese patent No. 7113415) and are proceeding with research and development to speed up breeding in the fields of medicine, agriculture, and livestock.
Setsuro Tech develops genome editing contract services for researchers in academia and companies using these proprietary technologies as well as providing genome-edited organisms to a wide range of industries. “PAGEs” aims to develop the genome editing industry and contribute to the well-being and sustainable societies.