The first effort by scientists in the USA to edit a human embryo using CRISPR has had extremely positive results.
Some background on CRISPR.
CRISPR, also known by the more technical name of CRISPR-Cas9, has quickly become the holy grail for genetic modification. It allows scientists to accurately edit specific genes they want to remove or replace in a target organism and it’s especially useful in the creation of vaccines. Up until now, it hasn’t been used much for the modification of human DNA, with good reason. China had, until recently, been the only country to experiment with CRISPR on human embryos and the results were a little startling. While CRISPR theoretically uses great precision, many sources have found that the side effects could be disastrous. Chinese studies conducted to try to remove genetic disorders from embryos proved to create many unwanted side effects and other CRISPR studies did likewise.
According to Silicon Republic, an attempt to remove a gene which causes blindness in mice had severe side effects, altering as many as hundreds of genes in the process of correcting the one intended gene. Algorithms exist to predict where these changes should take place, but their function is more suitable for individual cells than entire complex organisms. In fact, the risks of CRISPR are so well-established that the scientific communities in many countries are banned from using it on human embryos, except in instances when no other subject will suffice and when the research being done is to potentially treat a genetic disorder. With this in mind, a team of researchers based in the United States carried out their research, the results of which were published in Nature on August 2nd, 2017.
Where we are today.
The team managed to isolate and remove the genes leading to the development of hypertrophic cardiomyopathy (HCM). HCM affects .2% of people and is one of the most common causes of sudden death in athletes and the young. The researchers managed to remove MYBPC3, the gene which causes HCM in 72% of the embryos used, much higher than the success rate of 30% originally expected. What’s even more impressive and surprising, is that the team managed to remove the dangerous gene without any unintended mutations occurring elsewhere in the embryo’s DNA.
Apparently, one of the key factors in the team’s success was in the timing of the modification. While most teams have used CRISPR to edit embryos after fertilisation took place, this team did something quite different. Using stem cells from their male subject, who also supplied the sperm for the embryo, the researchers targeted the MYBPC3 gene for repair. When the donor’s cells divided, the most promising candidates were introduced to healthy donor eggs which were then fertilised with the donor sperm. This has not only resulted in more accurate modification, however. There was another, unexpected result.
According to The Verge, in some of the instances recorded, the male gene copied the healthy female’s gene, instead of the artificially designed template the researchers had inserted. Basically, this is a way that they hadn’t predicted embryos might repair themselves. The male genes took what they needed to complete themselves from the available eggs rather than the slightly more alien genes provided. This gives scientists great hope that CRISPR can become a truly reliable method to eliminate genetic disorders and diseases. What’s more, the surprising behaviour of the cells in seeking out healthy counterparts for its missing genes from the female should allay fears that genetic modification will lead to a race of genetic super-humans or designer babies gone awry. CRISPR, it seems, will help keep humans healthier and stronger, but still very much human.