The past week was quite busy, and unfortunately, I had to move my flight to the US because my visa hasn’t arrived on time. On the upside, I am able to spend some more time with friends in Frankfurt before I leave next week.
In today’s post I’m going to take a closer look at CRSPR Cas9. In the last couple years, its been the subject of controversy due to Genetically modifying, along with other species, human babies.
What’s CRISPR cas9?
It is an enzyme, a protein with a catalytic function, which was first discovered in the adaptive bacterial immune system, and is not naturally produced by us, humans. Originally, CRISPR cas9 protects the bacteria from reoccurring viral infections. After a viral infection, the bacteria incorporate the viral DNA into its own DNA repeats, like a book into a library. When the same virus infects the bacteria again, the bacteria uses the ‘saved’ viral DNA in its library and sends out CRISPR Cas9 to destroy any DNA that looks like it (i.e. has a complementary sequence).
The mature CRISPR Cas9 molecule is made up of 2 parts: an endonuclease and a single guide RNA template. The viral DNA I described as book above, is the single guide RNA, which is taken out of the library and incorporated into the Cas9 protein.
The whole process is kind of like ‘where’s waldo?’ – you know what he looks like but have to look pretty hard to find him, like finding a needle in a haystack – waldo being the single guide RNA to be found in the haystack of the cellular nucleus.
When the gRNA aligns to a DNA sequence, the Cas9 endonuclease acts as a scissor that cuts DNA, thereby destroying it, and removing the functionality of that specific gene. This can be done in living cells and applied to almost all eukaryotic species, making it a promising tool for genetic modification – particularly in the long run, for removal of pathogenic genetic mutations in the mammalian genome. (e.g. in cystic fibrosis)
https://www.youtube.com/watch?v=2pp17E4E-O8 (nicely detailed but simple explanation of CRISPR Cas9)
Designer babies – the norm for the future?
That all sounds very impressive and positive, however the positives always bring negatives with it: You can edit ANY gene, in theory. Which can be misused to edit any gene-defined trait you want, such as eye color or height. Which brings us to an ethical branch point, where the line is to be drawn between beneficial and medically relevant vs. messing with natural, genetic variation in populations.
Luckily, as with everything in life, gene expression is not as simple as turning a gene ‘on’ and ‘off’. Its much more complicated with genetic linkage, expression mechanisms and sequence variation, which causes gene expression to not be black and white, but rather 5000 shades of grey in between – and messing with gene sequences and expression without knowing the full impact it could have on the individual, is a risky business.
Therefore, realistically ‘designer babies’ in the sense of commercially ‘ordering’ babies is not going to be, in my opinion, the big next thing – at least for while, as we simply know too little about the consequences of genetic modifications on the long term health. Nevertheless, its potential to be misused for any chosen purpose in experimental settings is something to be kept in mind and, I have no doubt, will be the subject of controversial news for years to come.