Three chimera monkeys were born in a lab at the Oregon National Primate Research Center recently. To create these chimera primates, scientists inserted a combination of genes from several monkey embryos into a new embryo, accomplishing a feat that had been previously only demonstrated in less complex species.
Previously, knockout mice have become powerful tools for scientists studying genetic diseases including Parkinson’s and obesity, but the techniques were not applicable to primates. Knockout mice are created by fusing together mouse embryonic stem cells in a lab dish and then culturing those cells into a mouse embryo. But with the more complicated primate embryo, the cultured stem cells do not integrate so easily.
So, instead of using pluripotent stem cells, Mitalipov and colleagues decided to use totipotent cells from an earlier stage of embryo development called the morula stage. Unlike pluripotent cells, which can develop into almost any cell type in the body, the totipotent can form an entire animal as well as the extra-embryonic placenta.
“Monkey embryonic stem cells failed to contribute to any tissues or organs in our test, while stem cells directly taken from embryos formed normal offspring,” said Mitalipov.
In a paper published in the January 20 edition of Cell, the researchers describe placing totipotent stem cells in a culture dish and watching as 90% of the embryos grew into blastocysts over several days. Then, 10 chimeric embryos were implanted into five female rhesus monkeys, three of which were carried to term by female rhesus monkeys.
In the end, the three offspring were named Roku, Hex, and Chimero. They all have gene traits and lineages from as many as six embryos, which is why they’re labeled chimeric, from the Greek mythological creature made up of parts from various animals. Roku and Hex are the Japanese and Greek terms for “six.” Although the three primates carry traits from both sexes, they will develop as male monkeys.
“The future implications of our study are that we might need to study more natural stem cells in embryos and derive a new class of ESCs that would maintain their original qualities. This would translate into establishment of more potent human stem cells for regenerative medicine,” said Mitalipov.
References
- Tachibana, M., M. Sparman, C. Ramsey, H. Ma, H.-S. Lee, M. C. Penedo, and S. Mitalipov. 2012. Generation of chimeric rhesus monkeys. Cell (January).
