At the National Institute of Genetics, nine wild mouse strains have been established. These strains have characteristics not found in laboratory strains, such as marked genetic differences between different strains and behavior characteristic of wild mice.
These series of wild strains, named the Mishima Battery, are provided to researchers in Japan and overseas as highly unique resources, and are used for various research in the fields of cancer, immunology, development, and behavior. However, in spite of these excellent characteristics, wild strains have the problem of being difficult to apply genetic engineering technology.
In collaboration with Shigei Medical Research Institute and RIKEN, technical staff Yuji Imai and Associate Professor Tsuyoshi Koide of the Mouse Genomics Resource Laboratory have applied genome-editing using i-GONAD method, which does not involve any ex vivo manipulation of unfertilized or fertilized egg. The group showed that it is possible to efficiently modify genes in most wild strains by using this method.
First, in vitro fertilization was performed on the experimental strain C57BL/6 (B6 strain) and nine wild strains to investigate the efficiency of in vitro fertilization necessary for general genome editing experiments. As a result, it was found that only two wild strains were able to perform in vitro fertilization with the similar efficiencies as the B6 strain, and the other strains were extremely inefficient. Therefore, we applied a method called i-GONAD, developed by Professor Masato Otsuka of Tokai University, to wild strains, which performs genome editing without ex vivo manipulation of fertilized eggs. As a result, we succeeded in performing genome editing in 7 out of the 9 strains examined. This result indicates that it has become possible to efficiently perform genetic modification using wild strains in the future, and the use of wild strains in many research fields can be expected.
Figure: Overview of genome editing with the i-GONAD method. (A) An illustration of the procedure for the i-GONAD method. (B) Use of genetically engineered wild strains can be expected in a variety of research fields.
