Originally written: Dec 1, 2018
Title: The Possibility that He Jiankui Failed in an Attempted Eugenics Experiment
December 1, 2018 - By now everyone has heard the news: Chinese biophysics researcher, He Jiankui genetically edited twin human babies. If not, you can read about him here:
https://en.wikipedia.org/wiki/He_Jiankui
Basically, He allegedly attempted, and failed, to genetically edit two human beings; an unethical, immoral act that has been condemned worldwide.
He claimed to have targeted a specific gene that would confer innate resistance to HIV. Details on his research remained murky, but some information has finally come to light, and many are saying he failed to properly edit the targeted gene, and therefore clearly had no idea what he was doing. Well, I agree wholeheartedly with the first claim; that he failed to properly edit the targeted gene. But I think he knew what he was doing, and it relates very sinisterly to the failed gene edit many outside academia appear to be mocking.
The technique He Jiankui used is known as CRISPR-Cas9. CRISPR is originally a primitive defence mechanism in a particular strain of bacteria. Scientists have adapted its use to be able to edit genomes, and the original purpose of this was NOT for human use, but as a powerful biomolecular tool in research. No gene-editing technique has ever been so precise.
There are 3 moving parts (plus your gene of interest to edit) to CRISPR:
The Cas9 enzyme: Enzymes are proteins that perform some kind of catalytic work, and Cas9 recognizes a specific 3-nucleotide code and then cuts double-stranded DNA.
The guide RNA: This is a single-stranded RNA molecule that can fold to form secondary structures. The folded part of the guide RNA fits (and holds on to) a groove/cleft in the Cas9 protein. The guide RNA also has an unfolded region that is exposed. This region is called the complementary region, and can be designed by the researcher to be complimentary to any DNA sequence. (RNA can exist as a single strand but can also be double stranded with another complementary RNA or DNA strand.)
The purpose of the guide RNA is to bring the Cas9 protein to a precise target on DNA to perform a double stranded cut. In eukaryotic cell systems, there are DNA repair mechanisms that look for and repair DNA damage. For example a double-stranded break in DNA will activate these repair pathways, and the DNA will subsequently be fixed.a DNA donor fragment to edit your genomic DNA: This can be anything the researcher wants, such as an edit to the sequence of the gene or an addition of new DNA to the gene (ie. green fluorescent protein).
It’s more complicated than this of course, but basically when the cell’s DNA repair mechanism is activated by Cas9 cutting it, and if a DNA donor is present in the mix, then the repair mechanism will edit (incorporate) that DNA donor into the genomic DNA.
The gene He Jiankui targeted was CCR5. This is a receptor of chemokines (small proteins that instruct cells in our bodies to do stuff; primarily tells them to move). It is found on the surface of white blood cells. In mice it was shown that a deletion of the CCR5 gene resulted in improved memory. It has also been shown to be a powerful suppressor of neural plasticity, memory, and learning. Keep this in mind, as I intend to get back to this.
In HIV infection, it has been shown that a 32 nucleotide deletion in the sequence of the gene results in a premature stop codon and produced a non-functional receptor. HIV requires this receptor to gain entry into cells for infection. The reason scientists are interested in this specific mutation in the CCR5 gene is because there is a small percentage of northern Europeans that have this exact mutation, which has made them immune to HIV.
It was originally believed, and touted by He Jiankui that he achieved this mutation in the CCR5 gene that renders people resistant to HIV… well, as it turns out, he ultimately has admitted he did NOT replicate the mutation, but claims he still hoped to mimic its effects. THIS MAKES NO SENSE AT ALL! No qualified biophysicists, or molecular biologist would ever claim they would “hope” for intended effects from a failed edit. This is absolutely ludicrous.
According to an article published in the Journal of Law and the Biosciences (Greely, Henry T., 2019): “In both twins, some of the cells had modified CCR5 genes (one copy for one twin, both copies for the other) while other cells did not. They are what geneticists call ‘mosaics’, people with cells that have somewhat different DNA. And for neither twin did the CRISPR construct do exactly what it was intended to do: cause that deletion of a specific string of 32 base pairs, resulting in the CCR5Δ32 found naturally in some humans. Instead, it made several changes in the twins’ CCR5 genes, changes that apparently would lead to the production of non-functional protein, but changes that had never been seen in humans before. At the same time, He [Jiankui] reported that the CRISPR construct had not altered any of the other genes of the babies.”
Given this, then there are three basic problems with Jiankui’s CRISPR babies:
The intended mutation was not generated. Instead, novel mutations that have never been seen in humans were made, and there is no way to know how these novel mutations will manifest themselves as the CRISPR babies grow.
The twins were heterozygous for the edits made to CCR5. Generating a heterozygous edit is a problem with CRISPR: you can only generate an edit in one strand of DNA.
A little background: DNA has two strands. Each strand is a copy of a gene. We all have two copies of every gene. This means that we can have different variants of particular genes. This is called heterozygous. If one has two copies of the exact same variant of a gene, then it’s homozygous. CRISPR generates heterozygous edits, with homozygous edits being very rare. For the CCR5 edit, in order to see the true effect of the edit.... for instance the effect of resistance to HIV, the edit must be homozygous.
In addition to being heterozygous (for unintended edits nonetheless) the twins had mosaicism: not every cell in the twins had the edit. In the developing embryo only a subset of cells had successful CRISPR edits and this resulted in mosaicism. This is a challenge when targeting more than a single cell to be edited by CRISPR. There is no technique that ensures every cell will be edited. Again, this is another reason why it may not be possible to observe the effect of editing the CCR5 gene when performing the CRISPR experiment in multicellular human embryos.
In this Newsweek article, an ethical scientist makes an excellent point: That Jiankui could have tested the CCR5 edit in cell culture first, before moving on to editing human beings! Jiankui could have edited the CCR5 gene in immune cells to make it non-functional, exposed them to HIV, and then determine if the edited immune cells take up HIV or not. This is REALLY BASIC science-based lab practice worldwide. Additionally, Jiankui could have tested the embryos to ensure the CCR5 edit was made before allowing the embryos to progress to birth!
Jiankui allegedly did not want people to find out the identity of the twins, and it is clear he attempted to cover his tracks. As of this writing, no one has been able to track down the parents, or any family members of the twin girls. In addition to giving the girls made-up first names only, Jiankui left the names of the fertility doctors involved off his paper, and included a false date of birth for the girls. The rabbit hole is deep with Jiankui... just search the numerous articles popping up online. Just be sure to read from reliable sources, not like ScienceAlert.com, whose author of this article claims CRISPR is “imperfect” because it can cause “off-target effects”. No peer-reviewed research exists that supports this unfounded claim. Off-target effects, at worst, occur at extremely low frequency… ... that is if you know what you’re doing. There is a growing area of research that looks to minimize off-target editing in CRISPR.
At any rate, it is astonishing that Jiankui was unable to generate the desired CCR5 edit, yet generate novel mutations in that same gene. The efficiency and precision of a CRISPR experiment depends upon the guide RNA design. Every biophysicist, and molecular biologist in the world use RNA-prediction software (available free from multiple online sources), that take into consideration multiple variables that determine the efficiency and precision of guide RNAs.
It is well known that guide RNA can be engineered to be very precise, and it is equally well known that off-target effects can also be engineered to occur at low frequency. (in case you’re interested https://www.sciencedirect.com/science/article/pii/S216225311630049X)… something ScienceAlert.com might want to learn more about). So it’s mind-boggling that Jiankui didn’t generate his desired edit, but instead generated novel edits, not randomly as one might be led to believe from off-target editing, but in the exact gene he was targeting!
Recall that the loss of CCR5 has been shown in mice to improve cognition. I’m not sure what the exact edits Jiankui made to the CCR5 gene, but it seems rather suspicious that his experiment resulted in novel mutations never seen in humans before. It’s as if he purposely designed multiple guide RNAs to generate novel mutations that may have possibly resulted in complete loss of CCR5. After all, it’s easy to generate a knock-out mutation using CRISPR (“knock-out” as in a complete deletion of the gene).
Consider this: Had Jiankui simply knocked out the CCR5 gene, it would have been obvious to the world that he was trying to mimic the improved cognition experiment in mice. In other words, it would have been obvious to the world that Jiankui was engaged in an outright eugenics experiment.
So instead, he appears to have cleverly generated novel mutations that might result in complete loss of CCR5, but allegedly pass it off as if it were little more than a failed experiment in making humans resistant to HIV.
The jury is out, but journalists and others who are simply calling Jiankui an idiot for not knowing what he was doing, are missing what seems to be the elephant in the room. If you ask me, it appears this has all the hallmarks of an attempted eugenics experiment. This article from MIT Technology Review claims there is no evidence that Jiankui attempted to enhance cognition in the twins, but as suggested in this blog post, I wouldn’t be so quick to arrive at such a conclusion.
Irregardless of his intentions, He Jiankui has acted unethically. Of course everything here is alleged, but based on science.
Here is an article written in Science Magazine by one of the co-founders of CRISPR-Cas9, Jennifer Doudna that is well worth a read: https://science.sciencemag.org/content/366/6467/777.full