I’m a huge bookworm and for my birthday this year I received a copy of A Crack in Creation by Jennifer Doudna and Samuel Sternberg. I read it cover to cover in two days.
The book is a first hand account of the discovery of CRISPR technology, narrated by one of the researchers who co-invented it. CRISPR stands for clustered regularly interspaced short palindromic repeats and is basically just that; stretches of DNA found in bacteria. The CRISPR genes are flanked by CRISPR-associated (cas) genes and they are always found together.
CRISPR is a bacterial defence mechanism against parasitic DNA. Scientists realised that the CRISPR sequences matched that of virus that infect bacteria, known as bacteriophage or just phage for short. Once they had noticed this link, it was simply a case of discovering the underlying mechanism.
The Cas proteins were purified and several were found to have the ability to cut DNA at very specific points, using the CRISPR sequences as a guide. Cas9 is particularly important. Doudna’s team at Berkeley in the US made the monumental discovery that CRISPR-Cas9 is a hugely precise tool for gene editing that far surpasses the then-current tools of zinc finger nucleases.
Once Doudna and her collaborators published their work in 2012, the door to a new era of gene engineering was flung open with gusto. Scientists across the world began using the technology to edit genes in different species of bacteria, then plant and animal cell lines too. The beauty of CRISPR-Cas9 is that it is relatively cheap, simple and quick. Three very important qualities.
Doudna describes this high speed rollercoaster in the first part of her book. The most thought-provoking parts come later on, when she starts discussing the ethical considerations of this fledgling technology. Her primary concern is that it is only a matter of time before CRISPR is used to modify the human germline, tinkering with the cells that form embryos.
Why is this such a concern? Because edits in the germline are heritable. Modify the embryo and the changes are permanent, not only in that future person but also in any children that they may have.
Objections to this come from all angles. From those with religious views who believe it is unnatural to social equality advocates with concerns that an expensive technology will only deepen the socio-economic divides between those who can afford to modify their children and those who can’t. Designer babies bring an uncomfortable feeling to many. There is no getting away from the fact that you can’t ask permission from the person who is going to be affected. And could it be used as a sophisticated bioweapon?
It all sounds very doom and gloom but they are valid points that scientists cannot afford to ignore. CRISPR has the potential to unlock a whole new way to halt diseases like sickle cell anaemia or cystic fibrosis, just by altering the defective gene. It might be unethical to play God, but isn’t it more unethical to not investigate a promising candidate to alleviate human suffering?
In truth, I’m not sure on which side of the germline editing fence I sit. There are so many important considerations from whichever angle you choose to look. Doudna’s book covers the debates in extensive detail and I strongly recommend reading it. It is written so accessibly both in writing style and content. It is readable to any interested person regardless of their science background. Doudna drives home the importance of spreading the facts of CRISPR technology and of having debates about how it should be used. So I thought I’d do my bit. I’d love to hear your thoughts!
Rebecca | An Anxious Scientist