Gene editing is a method used to change the DNA of organisms such as plants, bacteria, and animals. These changes to gene expression, in turn, impact physical traits, or disease risk. Scientists use various technologies to do this, and many approaches of gene editing have been developed, most recently CRISPR-Cas9.
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The technologies used for genome editing act like scissors, cutting pieces of DNA in specific loci. These pieces can be removed, added to something else, or can replace the original DNA. The first genome editing tools were developed in the 1900s; many methods have been used to edit gene expression, but CRISPR appears to be the most dominant. CRISPR was discovered in 2009 and was developed from a gene-editing system in bacteria. The bacteria take bits of viruses and use them to make segments called CRISPR arrays. This allows the organism to “remember” related pathogens so that in the future, RNA segments from the CRISPR arrays will attack the viruses’ DNA. Cas9 is an enzyme that cuts DNA, thus disabling a pathogen. The CRISPR-Cas9 method works identically—an RNA molecule binds to the Cas9 and directs the “scissors” to a specific sequence of DNA to make an incision. Other enzymes may also be used such as Cpf1. Once the cut is made, scientists use the cells' DNA repair machinery to make changes to genetic material.
How is it Applied?
One of the main reasons why the CRISPR-Cas9 system is thought to be better than other methods is that it’s much more simple, efficient, and cheaper than older genome editing methods. There are several ways in which the system can be used to edit DNA.
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Gene editing is primarily tested on animals like mice since they contain similar genes to humans. So, by examining mice genes, scientists can predict the same type of changes that might affect human health.
The widely known potential benefit of gene editing is gene therapy. Gene therapies are treatments that involve gene editing to prevent and/or treat diseases, which may include cystic fibrosis and diabetes. There are two categories of gene therapies: Somatic and Germline.
Somatic gene therapy involves altering non-reproductive cells. These changes can only affect the patient or the person who receives therapy; thus, traits will not be passed down to a future generation. An example of somatic treatment would be a one-year-old girl in the UK receiving treatment for her leukemia, a form of cancer. In this situation, CRISPR was not employed. Instead, an alternative form of gene editing was used, known as TALENs. Gene therapies are still considered to be experimental, so it's vital to recognize the technical barriers of this treatment method.
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Germline therapy, the opposite of somatic gene therapy, involves the change of DNA in reproductive cells such as sperm and eggs. Therefore, changes made in the individual's DNA affect their offspring. For this reason, most people agree that scientists should not be able to make germline edits—and, if they do, to exercise caution.
Despite this, in 2018 a scientist claimed to have helped to make the first gene-edited babies. The twin girls, coming from an HIV positive father, were said to have their DNA edited to prevent them from getting HIV. In order to do that, He Jiankui, a genome-editing researcher at the University of Science and Technology of China, needed to disable the gene CCR5. This gene encodes the protein that allows HIV to enter a cell, thus preventing the genetic pathway to HIV. Fyodor Urnov, a genome scientist, was asked to review the documents that described the edited DNA sequences of the embryos at the locus of the CCR5 and confirmed that the editing had taken place. There has been no definitive evidence has come forward that the children are immune, but it's possible this event might alter further research in the future.
Whenever the topic of gene editing comes up, bioethics always seems to be a common theme, and this is because it is necessary for scientists to consider ethical concerns when it comes to safety. Mistakes in gene editing could potentially occur, such as cutting in the wrong spot, which could have unknown outcomes that may emerge in an individual or population. Other important questions to consider include:
Is the parents' consent enough to conduct gene therapy on an embryo?
Does gene therapy create larger health discrepancies?
Is it ethical to alter one's genes for the sake of athletic ability or appearance alone?
Is it acceptable to edit germline cells considering these changes will be apparent through family trees?
On a different note, the development of biotechnology has the potential to create job opportunities. As time goes by and more treatments rely on the use of gene editing, there would most likely be a demand for genetic engineers, seeing as the field still has more room to develop. The UK government predicts that 18,000 new jobs will be created in Britain alone by 2030, and the US bureau expects a 7% increase in careers for biomedical engineers and 13% for related scientists.
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The gene therapy industries will most likely need graduates with backgrounds in genetics, medicine, virology, bio and chemical engineering and business. Those in the pharmaceutical industry project that genome editing might become an important factor in the future of pharmacogenomics and healthcare as a whole.
As gene editing might have the ability to treat diseases with no cure, it’s important to do research on this field, recognize its benefits and concerns, and come to your own conclusions on where you stand in relation to the industry.
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Article Author: Idil Gure
Article Editors: Valerie Shirobokov, Sherilyn Wen