In the fight between the bacteria and the virus, it was the humans who got along. Crispr, a genetic editing technique based on a defensive system of bacteria, is seen as a promising way to combat numerous diseases, including cancer. In addition, it opened new work fronts in several areas of health, such as organ transplantation.
“Our DNA is a bunch of little blocks in sequence and, if there is a mutation there that causes damage, the system [Crispr] comes with the scissors and starts doing it as if it were surgery on the DNA, correcting this mutation”, says Ernesto Goulart, postdoctoral fellow at the Center for Human Genome and Stem Cell Studies at the University of São Paulo (USP).
Thus, Crispr makes it possible to inactivate, remove or replace small pieces of genes. To get to how this happens, one has to go back about a decade. In the early 2010s, several groups of scientists were studying how bacteria defend themselves against bacteriophage viruses. In a work with bacteria Streptococcus pyogenes, it was discovered that they did this with the help of an enzyme called Cas9.
“They discovered, in the genome of bacteria, repetitive sequences disguised as viruses”, says Goulart. These sequences are called Crispr. “When the bacterium was attacked by a virus, as these sequences were converted into RNA, Cas9 identified where one letter fit into the other and rendered the virus inactive.” There are Crispr techniques that use other Cas enzymes, but Cas9 is the most popular.
Based on these discoveries, researchers Jennifer Doudna and Emmanuelle Charpentier developed a new gene editing method. Compared to previous genetic engineering standards, Crispr-Cas9 is more accurate, faster, and incomparably cheaper. The duo won the Nobel Prize in Chemistry in 2020.
“It's difficult to talk about the limits of this technique, there are already many approaches, but we have clinical studies for the treatment of sickle cell anemia and hemophilia, for example”, says the USP researcher. Goulart works with Crispr in a line of research that may seem unusual: xenotransplantation.
The objective is to modify the genome of pigs to make the organs of these animals compatible for transplantation into humans. The researcher, whose career goal is to eliminate the transplant queue using innovative techniques such as Crispr and bioprinting, foresees an ambitious deadline for xenotransplants to become a reality.
“We want to be the first group in the world to do a xenotransplant”, he says. “And I believe we will do that in five years.”
Alongside this horizon of hope, Crispr also brings a worrying facet: the risk of using genetic engineering to change physical characteristics – eye color, skin tone, face shape – without any relation to disease. Today, the consensus of the scientific community is that this should not be done. “It will not be recommended to carry out genetic editions in germinal tissues”, explains Goulart. “We are only going to do it in somatic cells from adult individuals, so that changes are not passed on to the next generations.”
