Scientists Create Monkey Chimera With Fluorescent Eyes in Breakthrough

Chinese scientists have reported the creation of a monkey chimera—meaning an animal made up of cells from two genetically distinct organisms—with fluorescent green eyes and fingers.

While this seems pulled right from the pages of a comic book, the creation of animal chimeras using stem cells is being explored to further our basic understanding of biology, as well as genetic engineering and diseases. In the case of the live monkey born with fluorescent body parts, donated stem cells made up between 21 percent and 92 percent of its organs, the authors wrote in a study published on Wednesday in the peer-reviewed journal Cell. That’s a lot.

“Our results have major implications for the study of primate naive pluripotency [stem cells that can develop into differentiated cells] and genetic engineering of non-human primates,” the authors wrote.

The scientists—who hailed from multiple universities and state-funded labs in China—report that they used stem cells from two fertilized eggs belonging to monkeys of the same species: cynomolgus monkeys, also known as long-tailed macaques, which were housed “in sunny rooms” at the Chinese Academy of Sciences (CAS) Center for Excellence in Brain Science and Intelligence Technology.

The donated stem cells were marked with a green fluorescent protein, ensuring that concentrations of chimeric tissue could be identified by their greenish glow. Photos provided by the researchers show green fluorescence in the monkey’s eyes and in its fingertips. Chimeric cells were observed in large quantities elsewhere inside the monkey, including its brain.

“This is a long-sought goal in the field,” senior author Zhen Liu of the CAS said in a statement. “This research not only has implications for understanding naive pluripotency in other primates, including humans, but it also has relevant practical implications for genetic engineering and species conservation. Specifically, this work could help us to generate more precise monkey models for studying neurological diseases as well as for other biomedicine studies.”

The monkey only lived 10 days before its health “deteriorated with respiratory failure and hypothermia,” and it was euthanized. Another chimeric monkey only managed to develop into a fetus, which was aborted.

The development of chimeric animals has been ongoing around the world for decades. In 2019, Chinese scientists reported the creation of a human-monkey chimera using stem cells.

Despite its potential for providing a new source of organs for transplant, human chimera research is currently under a moratorium in the U.S. due to ethical concerns. However, recent polling has shown that a majority of the U.S. population supports such research.