May 24, 2020 I Paul Seaburn

Scientists Made a Mouse That’s 4 Percent Human

Scientists at the University at Buffalo announced they’ve bred a human-mouse chimera with the highest percentage of human cells ever … four percent. All together now:

“What could possibly go wrong?”

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In this pandemic time when conspiracy theories abound about how the virus could have escaped from a lab, all labs and all genetic experiments become questionable … especially those involving the creation of hybrids (offspring of two different species) or chimeras (one body with two sets of cells and two sets of DNA). While hybrids can occur in nature (think ligers (lion/tiger) and zonkeys (zebra and donkey)), chimeras are manmade. The accepted purpose for the human-animal chimera experiments (there have been human-monkey, human-pig and human-mouse chimeras) has been for creating sources of human organs for transplants. Yes, moral and ethical questions abound, which is why we don’t hear much about them. This one is different – it’s the subject of a paper published the journal Science Advances.

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Classic chimera

“In this study, we found that a transient inhibition of mTOR by Torin1 converted primed hPSCs to the naïve state, which could be maintained indefinitely in essentially the same condition used to culture mESCs. When injected in mouse blastocysts, naïve hPSCs generated a large amount of mature human cells of all three germ layers, accounting for 0.1 to 4% of cells in mouse embryos at E17.5 (embryonic day 17.5).”

The key phrases here are “mouse embryos,” “mature human cells” and “4%”. Researchers at the University at Buffalo and the Roswell Park Cancer Institute injected human stem cells into mouse embryos, implanted them in females and one eventually ended up with 4 percent human cells – the most in history. And this was not just a blob of human cells – many of the embryonic mice containing them had the cells in their liver, brain, eyes, heart, blood, and bone marrow.

Did he say human cells in a mouse brain?

“These events did not affect the function or welfare of the pregnant mice or the embryos because the embryonic eye was not capable of vision yet and the embryonic brain contained very few human neural cells to affect embryonic mouse brain functions.”

Does that make you feel any better? How about this?

“We did not detect contribution of human cells to germline tissues.”

Germline tissues are the ones that develop into eggs or sperm, so they’re implying that THESE human-mouse chimeras couldn’t pass the human cells, but the report doesn’t say that it would NEVER happen. If it’s any consolation, the mice embryos had to euthanized so the human cells could be located and counted.

It’s an extremely technical paper – far beyond the pay grade of this writer – but a quick scan found no evidence of actual human organs growing, which is the goal of these experiments. It also doesn’t appear that the researchers as of yet have any control over where the human cells ended up in the embryo. What if they had all settled in the mouse brain? Would the human part be able to think and ask “WTF?”

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At a time when the meat processing industry is under close scrutiny, research labs are being questioned more on security procedures, and medical experimentations are occurring far faster than regulators, watchdogs and ethicists can monitor them (often intentionally), is it any wonder that usage of the phrase “Let’s see what happens”  in animal experiments is fast becoming supplanted by “What could possibly go wrong?”?

We’ll know we’re in trouble when “What could possibly go wrong?” is replaced by:

“What do we do now?”

Or ...

"Have you seen the mouse?"

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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