A Chinese researcher announced recently that he has edited the genes of human babies with CRISPR-CAS9 technology. The scientific world is outraged. Read on why.
CAS9 is an enzyme that cuts DNA at sequences which are complementary to CRISPR sequences. It is present in bacteria, and they use the CRISPR/CAS system to cut viral DNA as part of the bacterial immune response. Jennifer Doudna (UC Berkeley), Feng Zhang (MIT) and other have harnessed this method to edit genes by deleting them, replacing them with other genes, or creating point mutations in them. For developing the CRISPR/CAS9 technology, these scientists are most likely to get the Nobel prize.
The problem with this approach, however, is that it is not specific enough. In addition to modifying the gene of interest, it can also modify other genes. If a CRISPR/CAS system can be created that selectively edits genes, then by injecting these proteins into cells that have mutant DNA, one could ‘correct’ the mutations and fix problems associated with mutations. The impact on human health could be enormous. The implications of this technology are only just becoming clear. In discussions with colleagues, I have speculated that this method could be used by unscrupulous scientists to edit germ line DNA- that is, edit the DNA of sperm cells and egg cells, to create new types of mutant humans. That has now come true.
The scientific world was shocked recently by a Chinese scientist, He, who edited the CCR5 gene in human embryos (read more here). Two girls, Lulu and Nana have been born, and a third baby is in the womb. The father of Lulu and Nana was HIV positive, and the mother HIV negative. The scientist claims that making the offspring HIV resistant by editing the CCR5 gene will now protect the baby from infection by the HIV in the father’s sperm sample. Of course, the sperm cells could just have been thoroughly washed before in vitro fertilization to remove HIV viral particles- why experiment with the embryo? One of the twin babies did not have copies of the gene deleted, which means that she is still susceptible. The other baby did have the CCR5 gene reading frame altered (that means the protein will not be produced). The big question is whether the ‘edited’ baby is indeed resistant to HIV virions.
Many scientists are up in arms against such research because this was a dangerous procedure. Other genes could have also been edited because the enzyme is not specific enough, although He claims that was not evident in the DNA sequence of the babies. But what if the CCR5 gene deletion has unintended side effects, because of loss of an as yet unknown function of the protein in the body? Will the child be normal? Maybe- read here.
What is going to be next? Will militaries of nations try to develop a new mutant human race by editing human embryos with CRISPR-CAS9? The technology certainly exists now.
It is unethical to experiment with human babies, even if it is for improving their resistance to diseases, because the CRISPR/CAS9 technology is not as clean as it needs to be, and we simply don’t know enough about the different functions a gene might have that could get lost by deletion. And yet, without such tinkering, we may never know because no amount of animal studies can prepare us for humans. Animal research is routinely defended with the justification that without it, many life saving drugs would not have existed today. But spare a thought for the poor animals. Tens of thousands of mice, pigs, rabbits, dogs, monkeys and horses are experimented on across the globe on a monthly basis. Why is it ok to perform CRISPR experiments on them, when it is obviously not ok to perform them with humans?