Tag Archives: CRISPR

Comments on That CRISPR Paper

If you’ve got a pulse and are interested in biology, you’ve probably heard that a team of scientists have reported successfully (well, kinda) conducting germ line editing on human embryos using the CRISPR-Cas9 technique. I started hearing rumors of this study around the time that a moratorium on germ line experiments in humans was being proposed by some Very Big Deals. With confirmation that the study is real, the bioethics and life sciences worlds are all a-twitter (somewhat literally).

There’s an ugly side to the current furor, and a lot of it has to do with the nationality of the research team. Apparently the fact that Chinese researchers conducted the study has given people cause for alarm. That there is straight up racism, seasoned liberally with some vintage Cold War nonsense; Kelly has gone over this in a lot more detail. I won’t say any more on this, except to remind that people that when I teach about unethical research, Nazi Germany and the United States of America account for the overwhelming majority of my examples. So let’s all keep a bit of perspective.

Risks, Benefits, and Arguments

Instead, I want to talk about this paper in the context of risks and benefits, and proposed regulatory action around CRISPR. Let me be clear: I think we need to proceed very carefully with CRISPR technologies, particularly as we approach clinical applications. There was a worry that a group had used CRISPR on human embryos. That worry was vindicated yesterday.

Well, sort of. Almost. Not really?

From where I sit, the central concern is best expressed in terms of the risks of using CRISPR techniques on potentially viable human embryos. Commentary in Nature News highlights this concern perfectly:

Others say that such work crosses an ethical line: researchers warned in Nature in March that because the genetic changes to embryos, known as germ line modification, are heritable, they could have an unpredictable effect on future generations. 

The central premises are that 1) CRISPR studies on viable human embryos could lead to significant genetic changes to the resulting live humans; 2) these genetic changes could have unpredictable effects on those humans; 3) the changes could be propagated through human reproduction; and 4) this propagation of changes could have an unpredictable effect on future generations. The conclusion is that we shouldn’t be conducting studies on viable human embryos until we’ve done a lot more research, and have a better mechanism for ethically conducting such research. I support this argument.

The conclusion doesn’t obtain in this case, however, because these embryos weren’t viable. As in, they are never going to result in human beings, and never were. They are “potential human beings” to about the same degree that the Miller-Urey experiment is a potential human being.

[The Miller–Urey experiment (or Miller experiment) was a chemical experiment that simulated the conditions thought at the time to be present on the early Earth, and tested the chemical origin of life.]

Above: not a potential human being.

What the study does show—conclusively— is that the clinical applications for germ line editing require substantial research before they are safe and effective, and this research should be approached with incredible care. The sequence the scientists attempted to introduce into the embryos only took hold in a subset of the embryos tested. Those embryos that did take the change, also produced many off-target mutations (unwanted mutations in the wrong places on the genome). And even when the embryos did show the right mutation, it was only in some cells —the resulting embryos were chimeras, in which some cells possessed the mutation, and others didn’t.

This experiment shows that you can use CRISPR-Cas9 on a human embryo. But that isn’t really a revolutionary result. What is important is just how marginal the success was in terms of a clinically relevant outcome. The conclusion we should draw is that even starting in vivo testing with viable embryos is not only hazardous (for reasons Very Big Deals have noted), but totally futile relative to less risky, more basic scientific inquiry.

Rather than an ethical firestorm, I view this research as an opportunity. This study is, more or less, proof that a robust, community-centered deliberative process is needed to determine what the goals of future CRISPR research are, and what science is needed, in what order, to get there safely. A moratorium on in vivo testing in viable embryos is a valuable part of this process.

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