Evolutionary history is the focus of my posts for a while, and what better place to start than CRISPR? Last week, Emmanuelle Charpentier and Jennifer Doudna’s work in using CRISPR for gene editing made news headlines – this is the first time the Nobel Prize in Chemistry has been awarded to two women. The future implications of gene editing on human life are extraordinary. But so too is our understanding of the CRISPR system, which is a blow to any hubris we might have about our evolutionary superiority — but a gain for the scientific progress that has allowed us to figure it out.
See, CRISPR is part of an immune system developed in bacteria and archaea: very simple organisms lacking cellular nuclei. These are among the earliest types of life on earth to develop: they go back about 3.5 billion years. And probably for nearly as long, these organisms have needed to defend themselves against viral pathogens trying to take them down.
Here’s the surprise: while having an immune defense against viruses makes perfect sense, the type of immunity CRISPR provides was shocking news to the biologists who discovered it. And this is because CRISPR is an *adaptive* immune response — something that was thought to have developed in our jawed-fish ancestors only about 500 million years ago. Adaptive immunity means striking against pathogens that a creature has already been exposed to — it is a system that learns, and one that has been associated with increasingly complex life forms.
But CRISPR works in single-celled organisms. When bacteria or archaea get invaded by a virus, they create a sequence of DNA mimicking the genetic material of the virus — the sequesnce is a CRISPR (“clustered regularly interspersed short palindromic repeats”) array. And then a protein (often Cas-9) cuts out that DNA in the cell – disabling the virus. And CRISPR can do this repeatedly.
The gene-editing abilities of CRISPR-Cas 9 are likely to change history in very large ways. For instance, recently a person had her DNA altered with CRISPR to cure her sickle-cell disease. This ancient immune system looks like it will shape the future of humanity.
Source(s): Medline Plus, “What are genome editing and CRISPR-Cas9?” Healthline, “First person treated for sickle cell disease with CRISPR is doing well,” Roz Plater July 6, 2020. Image Meletios Verras/Getty Images. Nobelprize.org/prizes/chemistry/2020/press-release. Sean Carroll, _Mindscape_ podcast, Fyodor Urnov, August 31, 2020, “Gene editing, CRISPR, and Human Engineering.
