Weighing the potential of genome editing

Weighing the potential of genome editing
PHOTO: The Straits Times

Tomatoes that don't rot as easily, bacteria-resistant crops impervious to mould, and even calmer tuna for easier breeding - biotech research has progressed by leaps and bounds through cutting and splicing genes, the blueprints of life, in a type of genetic engineering called genome editing.

Hailed as the "technology of dreams," genome editing has applications in a diverse range of fields. In medicine, for example, treatments could be developed for incurable diseases. But despite all the fervent talk of potential, there are just as many concerns over ethical implications and questions of safety that some believe are not being adequately discussed.

Treating the untreatable

Pioneered in the late 1990s by the United States, gene-editing technology is similar to editing words: DNA can freely be inserted and spliced from genomes to deactivate or modify the functions of certain genes.

A specialised enzyme is used in genome editing to modify genes with greater accuracy compared to gene technology in the past. Progress in this field surged after a superior enzyme was introduced in 2013.

Expectations are mounting for the use of genome editing in research for the treatment of incurable diseases. Hiroyuki Kugo, a professor at Tottori University and chief of its Chromosome Engineering Research Center, believes the technique will be a "vital tool for medicine."

At Kyoto University, a team of professors including Assistant Prof. Akitsu Hotta are working on treatment for muscular dystrophy, a group of diseases with no cure and characterized by the degeneration of muscles. They were able to edit and restore an abnormal gene after creating an iPS cell from the skin of a patient suffering from the condition, aiming to "develop the technique into treatment for muscular dystrophy."

Clinical trials are also under way in the United States for patients suffering from AIDS, in which their healthy immune cells are extracted and genetically edited to build up their virus resistance. These modified immune cells are then multiplied and reinserted into patients.

Ethics of 'designer babies'

As researchers press on, calls are growing for a temporary halt to genome engineering in the medical field - particularly for research involving genetic modification of human embryos. From enhanced disease resistance to above-average intelligence, the prospect of creating "designer babies" with superior genes is not far off in the future.

A group of scientists including US Nobel laureates published an article in science journal Nature in March, urging a moratorium on gene-editing technology as they called for "open debate."

Undeterred, a research team from China declared that they had successfully edited the genomes of human embryos in a paper published in April. The team was quoted in Nature as saying the technology was "still too immature," and attempted to address ethical concerns by stating they only used "nonviable" embryos that could no longer grow to term. The team didn't respond to e-mails about their research.

"Modified genes in embryos will be passed on to future generations, so there's wider repercussions to consider in terms of ethics and safety," said Edward Lanphier, president of Sangamo BioSciences, Inc., a US biopharmaceutical firm conducting clinical genome editing trials for patients suffering from AIDS.

In a similar vein, a statement released by the White House on May 26 said that "altering the human germline for clinical purposes is a line that should not be crossed at this time."

Japan remains cautious

In Japan, government research guidelines stipulate a ban on live births as a result of genetically engineered embryos, sperm and eggs - but experiments that don't reinsert embryos into the womb are permitted.

The Education, Culture, Sports, Science and Technology Ministry's Bioethics and Biosafety Commission said manipulating embryos using gene-editing technology "presents a serious problem. We'll continue to monitor developments."

Osaka University Prof. Yasufumi Kaneda, also chairman of the Japan Society of Gene Therapy, said that "studying the effectiveness and safety of genome editing has just begun."

"Hopefully we can have thorough discussions at academic conferences as well," Kaneda said.

Advances in crops, livestock

Researchers are also making advances in breeding genetically modified crops and livestock.

Hiroshi Ezura, a professor at the University of Tsukuba, is attempting to create rot-resistant tomatoes through genome editing. The technology can grow tomatoes resistant to rot in just under a year, which would normally take 10 years using drugs.

At Kyoto University, Masato Kinoshita and his team successfully bred larger red sea bream last year by deactivating a gene that was stunting muscle growth.

Researchers in the United States are pressing on with similar work to breed cows with higher meat yield.

But just how safe is genetically modified produce and cattle? According to Kazunari Kondo, a senior researcher at the National Institute of Health Sciences, "Safety has yet to be confirmed in terms of food." Genetically modified organisms could also adversely impact the ecosystem.

Such concerns are addressed in an international treaty called the Cartagena Protocol on Biosafety to the Convention on Biological Diversity, which aims to protect biological diversity from the "potential risks posed by living modified organisms resulting from modern biotechnology."

The wildlife division at the Environment Ministry said that "protocols have yet to be decided in terms of handling organisms created through genome editing, which were beyond our expectations, so research needs to be monitored carefully."

A precise method to modify DNA

A genome is an organism's complete set of DNA made up of four structural molecules known as nucleotides, sometimes called "bases." Think of them as words while DNA are like sentences.

To edit a genome, oxygen "enzymes" are used to cut long stringy DNA strands at sections indicated by "guide molecules."

By inserting different bases into incisions, genes can be rendered useless or modified.

Genome editing is far more precise than genetic recombination.

In the past, radiation and viruses were used to modify DNA in a tedious and lengthy process - scientists had to sift through large quantities of specimens to identify the desired mutations that occurred at random.

There were similar difficulties in hybridization for livestock and crops.

The latest gene-editing technology has pinpoint accuracy, significantly reducing reliance on such hit-or-miss methods.

Most of the key genome editing patents are held by US parties.

Japan had made progress with research on guide molecules led by scientists like Kyushu University Prof. Yoshizumi Ishino, but their use was also pioneered in the United States.

Japan could face a wealth of license fees amid talks to expand commercial applications for genome editing.

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