A new way to edit the human genetic code could in principle correct up to 89% of disease-causing DNA errors, say American scientists.
The technology, known as "prime editing", has been described as a kind of "genetic text editor" capable of accurately rewriting DNA.
In laboratory testing, the new technology was used to correct mutations that cause disease, such as sickle cell anemia.
The method was developed by the Broad Institute team, linked to Harvard University and MIT (Massachusetts Institute of Technology), both in the United States. The team of scientists say the technology is very versatile and accurate, but points out that research is just beginning.
Can we already edit DNA?
DNA is the "instruction manual" for the construction and development of every human body. It is present in almost all our cells.
The ability to alter DNA through gene editing promises to revolutionize medicine, but it also raises new moral and ethical questions, such as the controversial creation of genetically engineered babies for protection against HIV.
Prime editing is the latest advance in the field of genetic engineering, which is developing at a rapid pace.
One of the most revolutionary techniques in this field and which drew great attention was Crispr-Cas9, developed seven years ago.
It scans DNA for the right place to cut it and allow it to be edited, that is, for a gene to be deleted or inserted. The problem is that edits are not always perfect and DNA cuts can be made in the wrong place.
The advance brought about by "prime editing" brings greater precision.
How does prime editing work?
Research published this week in the journal Nature shows how scientists used the method to insert or delete sections of DNA. Prime editing is also capable of correcting smaller sections as a single letter of the three billion that make up the human genetic code.
"You can imagine prime editors as word processors, able to search for a target between DNA sequences and precisely replace it," says biochemist David Liu, one of the researchers. "Prime editors offer more flexibility to find a target and greater accuracy in editing."
The method can be compared to text editing on your computer: it's like pressing Ctrl-F to find a piece of text you want to change and then pressing Crtl-V to paste the new text you want to insert.
The technology uses a genetic code sequence made in the laboratory. This sequence has two functions: finding the part of the DNA you want to edit and introducing the changes you want to make.
This sequence is combined with an enzyme called reverse transcriptase, which "copies" the edits to DNA.
How can the method cure diseases?
DNA has four basic components, the nitrogenous bases: adenine, cytosine, guanine and thiamine. They are known by their letters A, C, G and T.
Three billion of these letters make up our DNA, the "complete manual" for body development and functioning, but tiny errors cause illness and disorder.
The most common form of sickle cell anemia (hereditary disease caused by anatomic alteration of red blood cells) is caused by a mutation that makes a specific A into a T.
Tay-Sachs disease, which affects the nerves and is fatal, is often caused by a mutation that adds four extra letters of code to the DNA.
Prime editing was successfully used to correct these two genetic errors in experiments done on human cells in the laboratory.
There are about 75,000 mutations that cause disease in humans. David Liu estimates that "prime editing" has the potential to correct 89% of them.
The other 11% include situations where the person has too many copies of a gene (a section of DNA responsible for a specific instruction) or when an entire gene is missing.
"Prime editing is the beginning rather than the long aspiration of molecular life sciences to be able to make any change in DNA from any position in a living cell or organism, including potential patients. humans with genetic diseases, "says Liu.
How long until the technology is available?
The big challenge now is to make it possible for the molecular machinery capable of making these edits to properly access the right parts of the human body.
Early applications are likely to be made in diseases where it is possible to remove cells from the body, edit them, ensure they are safe, and put them back.
This is applicable in the treatment of blood disorders such as sickle cell anemia and thalassemia, where bone marrow can be removed and placed back.
"We are able to 'correct' human mutations associated with disease, but the ability to do this on the right cell type and in a way that is applicable to clinical treatment will take some time," says molecular biologist Hilary Sheppard of University of Auckland.
What was the repercussion of this research?
Professor Robin Lovell-Badge of the Francis Crick Institute in London praised the study.
"Because the vast majority of human genetic diseases are the result of mutation types that can be corrected by prime editing, the method should be useful in therapies for these types of diseases."
"Of course it will take a lot more work to optimize the method and find ways to deliver components efficiently before they can be used to treat patients, but it sure has a lot of potential," he said.
Geneticist Helen O'Neill of University College London says the results are impressive.
"Research was done in vitro on human cells with examples from 175 editions, including some of the most difficult to treat diseases."
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