I am a bit behind in my reading, so just today I saw an incredible article in the February 27th issue of Science News. The article, entitled “From Skin Cells to neurons, with no middle man,” discussed some astonishing experiments in which mouse skin cells were turned directly into neurons.1
Researchers at Stanford University took skin fibroblast cells (cells that make a protein called collagen) from a mouse and used a virus to insert genes that encode certain transcription factors. These transcription factors are proteins that actually help to regulate gene activity. In other words, their job is to turn genes on and off. The idea here is that even though skin cells are specialized, they have the same DNA that any other non-reproductive cells have. Thus, if we could “turn on” the right genes and “turn off” other genes, we could turn one type of cell into another type of cell.
So…the researchers inserted genes for three transcription factors that are present when neurons are just starting to form. It is assumed that these transcription factors activate the genes necessary for a stem cell to become a neuron, and they deactivate the genes that a neuron doesn’t need. The researchers thought that if they forced those transcription factors to appear in a skin cell, the transcription factors would turn on and off the right genes to make the skin cell turn into a neuron. They were right.
The majority of the neurons produced in this manner acted like “normal” neurons. For example, they communicated with other neurons in the Petri dish, and they made proteins typical of neurons. They also made glutamate, which is a chemical used to excite other neurons.
So we learn a couple of things from this story. First, the assumption that only embryonic stem cells are capable of turning into any cell in the body is not true. Previous research has already shown that adult cells (skin cells, for example) can be induced to become what appear to be cells just as “flexible” as embryonic stem cells. Now we know that at least in the case of skin cells to neurons, you can skip the stem cell state altogether! Thus, it seems that adult cells are significantly more “flexible” than scientists previously thought. So the whole brouhaha over the necessity of using embryonic stem cells in medical research is just not true.
The other thing we learn from this story is yet another case in which the scientific consensus was dead wrong. It was the scientific consensus that the only way to make a new kind of cell was to start with a stem cell. There was just no way you could take one type of cell that had already specialized (like a skin cell) and turn it into another kind of cell (like a neuron). As the article says:
Scientists previously thought that such a transformation required taking cells several steps backward in development to become pluripotent stem cells.
Why did they think that? Well, once a cell “specializes” into a specific kind of cell and starts doing the tasks that kind of cell is supposed to do, it develops traits that are specific to its job. Its characteristics are also influenced by its surroundings. These things are called “epigenetic factors” – factors that are affected by something other than the cells’ genes. It was thought that these factors left a permanent impression on the cell. As the article says:
Researchers have thought that major changes, such as skin cells becoming neurons, were nearly impossible unless the epigenetic slate was wiped clean, as it is with induced pluripotent stem cells.
So once again, the scientific consensus is shown to be wrong. Something the scientific consensus thought “nearly impossible” has been shown to be quite possible. It’s too bad politicians listened to that scientific consensus and made policies based on it. I desperately hope they learn their lesson, but I don’t think they will. When people don’t want to think for themselves, they just rely on the scientific consensus, and that leads to all sorts of problems.
Unfortunately, it is hard to think for yourself, and that’s why many people just don’t want to do it.
1. Tina Hesman Saey, “From skin cells to neurons, with no middle man,” Science News February 27, 2010, pp.5-6
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