Researchers expand DNA helix to forge entirely new stable organisms

24 Jan 2017

DNA helix model. Image: Sigrid Klop/Shutterstock

Paving the way for an exciting future of drug discovery and treatment, researchers have for the first time developed a stable semisynthetic organism by expanding its DNA helix.

Since the first organisms formed on Earth millions of years ago, to humans today, DNA has been defined by its code of four letters: G, T, C and A.

Now researchers from The Scripps Research Institute (TSRI) in the US are forging a whole new path for what the definition of life is, after forging the first new semisynthetic organisms with an expanded DNA code.

Offers hope for future drug discovery

In addition to G, T, C and A, these new organisms also hold as two synthetic bases called X and Y in its genetic code that was first synthesised by TSRI professor Floyd Romesberg and his colleagues in 2014.

Returning three years later, Romesberg and his colleagues have published the findings of its newly created organisms in the journal Proceedings of the National Academy of Sciences.

Back when the team first expanded the genetic code in 2014, it was able to show that modified E coli bacteria could hold this synthetic base pair in their genetic code, but it could not keep the base pair in their code indefinitely as they divided.

This time however, stable semisynthetic organisms have been created in the lab, opening a whole new world of scientific research, particularly as a way to create new functions for single-celled organisms that play important roles in drug discovery and other breakthroughs.

TSRI scientists

Prof Floyd Romesberg (right) and graduate student Yorke Zhang, who led the new study at TSRI, along with Brian Lamb (not pictured). Image: TSRI/Madeline McCurry-Schmidt

“Your genome isn’t just stable for a day,” Romesberg said on the breakthrough. “Your genome has to be stable for the scale of your lifetime. If the semisynthetic organism is going to really be an organism, it has to be able to stably maintain that information.”

These semisynthetic organisms were created with help from Romesberg’s graduate students Yorke Zhang and Brian Lamb, who optimised a tool called a nucleotide transporter, which brings the materials necessary for the unnatural base pair to be copied across the cell membrane.

Then, with the help of exciting CRISPR-Cas9 gene editing technology, the team designed its organism to see a genetic sequence without X and Y as a foreign invader.

‘All of life’s processes can be subject to manipulation’

A cell that dropped X and Y would be marked for destruction, leaving the scientists with an organism that could hold on to the new bases, surpassing previous attempts by nature to stop X and Y from stably multiplying.

“We can now get the light of life to stay on,” Romesberg said. “That suggests that all of life’s processes can be subject to manipulation.”

Easing fears that this will turn into a Gattaca­-like world of enhanced superhumans, Romesberg said that the research is still at a point where there are no applications as yet, only the ability to get the organism to store genetic information.

However, in the future, the researchers plan to study how their new genetic code can be transcribed into RNA, the molecule in cells needed to translate DNA into proteins.

Colm Gorey was a senior journalist with Silicon Republic