ES from SCNT: Another Human Stem Cell Milestone
Human embryonic stem cells have been created using a technique called somatic cell nuclear transfer (SCNT) for the first time. Interestingly, SCNT might be the oldest genetic reprogramming technology in our biological arsenal, but its use in creating human ES cells has proven elusive.
We’ll get to the news in a moment, but first some history. In 1958, John Gurdon made a frog from a tadpole.
“Congratulations, John, that’s how frogs are usually made. Big whoop.”
Except that he did it by inserting the nucleus from a tadpole cell into a frog egg that had its own nucleus removed. It should have been immediately clear to everyone how cool this was, but it took 54 years for him to get the Nobel Prize, which he shared in 2012 with some other stem cell reprogramming pioneers.
Why did that work? It makes perfect sense when you think about the job of an egg. Compared to sperm cells, eggs are huge. They are Death Stars and sperm are X-wings, each looking for an exhaust port into which they can shove their half of the genetic material. The egg is stuffed full of the proteins, mRNAs and other biological machinery that it will need to hit the ground running and begin the process of development. In other words the sperm just brings genes to the party (there’s a joke in there somewhere). The egg is the pilot, engineer and tech support. (For the genetics fans out there, this is also why maternal effects exist)
In a sense, the egg is a big bag of stuff that will define what the embryo is, at least for the first several cell divisions. Somewhere in all that eggy cytoplasm is a set of factors that are primed and ready to lead the way to embryoville.
Wait … where were we again? Oh yeah: Human stem cells.
So while SCNT technology has been around for a while (and has been used to create some very famous sheep), it never worked in humans (despite a faked claim in 2005). The process of removing and replacing the nucleus of donated human eggs was too disruptive. Until the new report in Cell last week.
Using donated eggs (obtained by consenting women from certfied IVF clinics) robbed of their own nucleus, a whole skin cell was injected and given an electric shock to stimulate cell division. That that even works is amazing. But the harvested stem cells acted like normal ES cells, and appear to be just as useful. They can be used to create patient-matched cells to study specific diseases in the petri dish, or engineered into neurons and other tissues to implant into a donor’s own body. All without destroying embryos.
Of course, we can already make near-embryonic stem cells by directly reprogramming skin cells with a simple genetic cocktail. So does it make sense to seek out egg donations for a technology like this? The ethics of making an economy out of egg donation are murky. And of course, there’s the worry that instead of just being used for making stem cells, it could be used to clone an entire human. That’s completely illegal, but it’s worth considering, at least.
It’s a new step forward in our ability to understand and manipulate human biology, and the advancement of knowledge like this is always worthy of excitement. Look at what power we hold! But we are men and women, not gods … and that’s what makes this all the more remarkable.
