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article imageEssential Science: First U.S. case of human embryo gene editing

By Tim Sandle     Jul 31, 2017 in Science
U.S. researchers based in Oregon have performed of gene editing on human embryos. The researchers corrected defective genes responsible for inherited diseases in several embryos using the gene editing technology CRISPR.
Genome editing has the potential to cure diseases by disrupting endogenous disease-causing genes, correcting disease causing mutations or inserting new genes with protective functions. The technique enables researchers to specifically target a region of DNA and add or remove genes. However, gene editing is a controversial practice, with supporters and detractors across the science field. The first studies were undertaken in China, where a gene responsible for a blood disorder was edited out.
The U.S. research was undertaken in such a way as not to break current was. The U.S. Congress has blocked clinical trials that involve genetically modifying human embryos (where the debate was under an umbrella term, used by much of the media, as “designer babies.”) The new research from Dr. Shoukhrat Mitalipov, who works at Oregon Health and Science University, was never intended to go to clinical trial. The germline engineering did not allow the embryos to develop for more than a two days, and the embryos were not intended to be implanted into a womb (the embryos were destroyed after just a few days).
CRISPR -  revolutionary new tool to cut and splice DNA.
CRISPR - revolutionary new tool to cut and splice DNA.
UC Berkeley
As one of the scientists said (quoted by Engadget):
"It is proof of principle that it can work. They significantly reduced mosaicism. I don't think it's the start of clinical trials yet, but it does take it further than anyone has before."
The aim was pure research, to see if CRISPR could be used to edit embryos without causing the generic error mosaicism (the presence of two or more populations of cells with different genotypes in one individual). Results of the peer-reviewed study are expected to be published soon in a scientific journal.
Representative image of the region of the brain affected by Huntington Disease.
Representative image of the region of the brain affected by Huntington Disease.
Susann Schweiger
READ MORE: Scientists place a GIF image inside a living organism's DNA
Both the U.S. and Chinese studies were undertaken to see if it is possible to use CRIPR to permanently alter the genomes of our descendants, in order to eradicate disease-causing mutations.
What is CRISPR?
CRISPR (an acronym for “Clustered regularly-interspaced short palindromic repeats”) is a relatively new genome editing tool that functions like molecular scissors. The method allows scientists to modify an organism’s DNA (many studies have been performed on the E. coli bacterium, for example).
The CRISPR gene editing technique is, theoretically, a very efficient way of disabling genes, by introducing small mutations that disrupt the code of a DNA sequence. CRISPR can also be used to repair genes.
Physics simulation of 5 megabases of DNA forming loops and domains.
Physics simulation of 5 megabases of DNA forming loops and domains.
Courtesy of Adrian Sanborn, Erez Lieberman Aiden
The potentials with the technology range from treating and curing rare genetic diseases to agricultural advances through the modification of food. There’s also, as discussed, the potential to edit the genes of embryos.
READ MORE: Is CRISPR technology set to change biological science?
Controversy
The primary risk concern with gene editing is that a therapy will have “off-target effects”, changing other genes. The reports of the new U.S. test has not been welcomed by all scientists. For example, the Center for Genetics and Society (CGS) Executive Director Dr. Marcy Darnovsky, for example, said in a communication provided to Digital Journal: “This development should be a wake-up call for everyone who cares about responsible science… We call on scientists around the world to refrain from research aimed at refining gene editing for use in human reproduction; for policy makers to strengthen global rules prohibiting human germline modification; and for researchers and policy makers to create meaningful processes that promote public participation.” Instead of gene editing, the organization calls for embryo screening techniques, such as testing IVF embryos and implanting only disease-free ones. According to New Scientist, there are only a small number of cases where this method (preimplantation genetic diagnosis) will not work because neither of a couple’s embryos are disease-free.
The structure a DNA molecule depends on its environment.
The structure a DNA molecule depends on its environment.
Richard Wheeler
However, the counter debate is if we already use gene therapy to fix faulty genes in children, then why not intervene earlier and prevent them ever becoming ill? CRISPR is potentially the most powerful tool available to scientists for this purpose.
Future possibilities
For advocates of the technology, however, the use of CRISPR with embryos promises the elimination of many inheritable diseases and this has sparked the interest of several global companies (although, at this stage, work with embryos remains within certain research institutes under their respective government licenses). The use of CRISPR with embryo should not be muddled with the general explorations of CRISPR with, say, bacteria (which do not trigger the same levels of controversy). In some parts of the world, gene editing is being used in experimental therapies for things like sickle cell disease and cystic fibrosis.
Genome editing of somatic cells, in particular, is a promising area of therapeutic development. This is the area of focus in China where Sun Yat-sen University in Guangzhou scientists used complex enzyme-editing tool CRISPR-Cas9 as a therapeutic agent to eradicate the human β-globulin (HBB) gene from the germline of the human embryo. The mutations in HBB gene cause β-thalassaemia (a deadly blood disorder).
In the U.S., what is likely to shift ground is a review by the Committee on Human Genome Editing. While the U.S. government does not currently allow gene editing of embryos where the embryo is allowed to mature, the committee has indicated that germline editing could be permitted in the future, if properly regulated and with public approval.
If approval is eventually given there is likely to be a debate around the approval of important treatment while avoiding ‘enhancement’. is often blurred. What would happen, for example, if medics in one region wished to modify aspects of human physiology to adapt to climate change? Would this be appropriate?
With further developments, building on the case in China or the U.S., there remains a log-way to go and there are still a lot of technical difficulties to doing precision editing in human embryo cells. For instance, as it stands the application of CRISPR technique involves risks since it may produce off target mutations, which can be deleterious.
The following video from New Scientist, outlines the current state of the technology:
Whether gene editing an important biological science for treating existing patients or a force for ill, to be used to control the traits of future generations, is a philosophical and political debate that needs to continue.
Essential Science
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This article is part of Digital Journal's regular Essential Science columns. Each week Tim Sandle explores a topical and important scientific issue. Last week we profiled an interesting development in robotics, where an elongated plant-like robot had bee showcased. Then week before we looked at how the human microbiome is now being digitized in order to take advantage of the findings from the Human Microbiome Project and develop personalized medicine.
More about Gene editing, Crispr, CRISPRCas9, Genes, Genetics
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