In a world's first, Japanese researchers have succeeded in producing a set of immunodeficient marmosets using genome-editing technology, allowing them to study disease symptoms that are much more similar to those in people than in mice.

Genome editing has been used to create mice before, but primates have been technically difficult to engineer. This study marks the first time a disease has been re-created in a primate's body using this new and highly precise type of genetic engineering.

Using this method, the scientists inserted a DNA-cutting enzyme programmed to disable immune functions into the fertilized eggs of marmosets, creating 21 monkeys with far fewer immune cells than normal monkeys. Three of the 21 marmosets are still alive, having survived for more than a year, researchers said.

The research will go a long way in studying the complex biology of human diseases, which are hard to study with mouse models and which involve functions such as thoughts, memory, learning and judgment, according to Erika Sasaki, a geneticist at the Kawasaki-based Central Institute for Experimental Animals who led the project.

"By applying this technology, we can in the future create monkeys with neurological diseases or diabetes. Since marmosets exhibit symptoms that are very similar to humans, it is hoped to help with the development of new treatments," Sasaki said.

She also said immunodeficient marmosets can be used to monitor what happens when organs such as the pancreas or nerve cells made from iPS (induced pluripotent stem) cells are transplanted.

"Since the engineered marmosets would have less immune reaction to transplanted organs, we can watch their progress for a much longer time," she said.

The joint research by CIEA and Keio University in Tokyo was published Thursday in Cell Stem Cell, a journal published by the Cell Press.