The Good, the Bad, and the Ugly of Genetic Chimera

In Greek mythology there was a fire-breathing, three-headed she-monster with the body and head of a lion, a goat’s head coming from the lion’s back, and a serpent for a tail. Called KHIMAIRA (Chimera), the Greek hero, Bellerophon killed her. Today the chimera is no longer a myth but a reality. Here is the good, bad, and ugly of genetic chimera created in a laboratory. 

Image of a bronze statute of the Greek mythological monster called Chimera--not a genetic chimera
Public Domain image from the National Archive Museum in Florence via Wikimedia

Genetic Chimera

The term genetic chimera refers to a single organism composed of two or more genetically different cells. There are innate (natural) plant and animal genetic chimeras. Human chimeras were rare, or so we thought. That condition may be much more common than we assume. Most human chimeras never know they have the condition. They may have a liver with a DNA that matches the rest of their body, but their kidneys have a different DNA.

Synthetic chimera gain their unique genetic makeup through transfusion or transplantation. Human organ transplants create a synthetic chimera.

You’ve probably seen a sensational crime story where the criminal escapes because of his or her chimera blood type. And you’ve probably seen the recent sensational science news about a lab created monkey-human chimera.


Image of a mouse chimera with her pups. Momma mouse has is a lab created genetic chimera with a multi colored coat and one red eye. Babies are brown but carry the gene for mom's coat and eye color.
Public Doman image from Wikimedia

Scientists created chimeric mice in 1961. They created these chimeras in the laboratory to study gene function. And they learned a lot.

Then, scientists realized that since sheep and goats could have live offspring that were sheep-goat hybrids, they might be good experimental subjects for chimera. Scientists created the sheep-goat chimera in 1984.

Researchers hope to learn more about regenerative properties and perhaps create a part human chimera to produce organs for much needed transplants.

Then in January 2012, scientists introduced three rhesus macaques, Hex, Roku and Chimero, to the world. Scientists had mixed parts of six different embryos and created new embryos. They implanted those embryos into mama monkeys who then gave birth twins Hex and Roku and a singleton, Chimero.

Shortly after that the United Kingdom developed the Human Fertilization and Embryology Authority and in the United States developed the Embryonic Stem Cell Research Oversight Committee. They developed both to review human embryonic stem cell research, including part-human chimera research.

Research in China doesn’t face such regulatory oversight.

The First Human-Monkey Chimera

The Chinese Academy of Science’s Kunming Institute of Zoology created the first human-monkey chimera in July 2019, a Spanish scientist, Professor Juan Carlos Izpisua Belmonte, from the American Salk Institute in San Diego led the project in collaboration with the Murcia Catholic University in Murcia, Spain.

The team took macaque monkey embryos and injected them with human stem cells, to see how these distantly related animal cells might coexist as one. The researchers determined that the human cells had successfully integrated in 132 of the macaque embryos, and after 10 days, 103 of the chimeric embryos were still alive and developing. They destroyed the remaining three living embryos on day 19.

The Ethical Questions

How to Write a Good Story

Human-nonhuman chimera research has been going on for a while. But we heard of the human-monkey chimera, many of us became alarmed. Why? Perhaps because monkeys are a species that are closely related to humans. Perhaps because we imagine a monstrous-to-us part-human, part-monkey creature walking amongst us.

Researchers seek answers to better understand genetics. They think their research may lead to cures or organs to transplant into patients who need transplant to survive. These are wonderful goals, aren’t they? But does the end justify the means?

Things to Think About

If we want to stop testing women’s cosmetics on lab animals, should we continue genetic research on embryos? Is it okay to have a rat or a pig-human chimera but not a monkey-human chimera? Who should regulate these experiments? And finally, if science can create a human-nonhuman chimera that is an organ match to humans in need, what rights does that human-nonhuman deserve?

Ethical questions about genetic research are occasional topics on this blog. If you find this interesting, check out this previous post about conservation genetics.

This is just the tip of the Good, the Bad, and the Ugly of genetic chimeras created in the laboratory. Do you have concerns about chimeras created in the lab?

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