Scientists Insert Man-Made Chromosome Into Yeast

Lee Rannals for redOrbit.com – Your Universe Online

An international team of researchers have taken an important step in the field of synthetic biology, bringing scientists closer to manufacturing microorganisms that could produce biofuels or even medicines.

Scientists reported in the journal Science this week that they have synthesized the first functional chromosome in yeast using a computer-aided system.

“Our research moves the needle in synthetic biology from theory to reality,” Jef Boeke, director of NYU Langone Medical Center’s Institute for Systems Genetics, said in a statement. “This work represents the biggest step yet in an international effort to construct the full genome of synthetic yeast.”

The researchers were able to build a fully functioning chromosome using a computer and successfully incorporated it into brewer’s yeast, or Saccharomyces cerevisiae. In all, they tied together about 273,871 base pairs of DNA and made more than 500 alterations to its genetic base by removing base pairs deemed unnecessary to chromosome reproduction and growth.

[ Watch the Video: Scientists Synthesize First Functional ‘Designer’ Chromosome in Yeast ]

“It is the most extensively altered chromosome ever built,” Boeke said. “But the milestone that really counts is integrating it into a living yeast cell. We have shown that yeast cells carrying this synthetic chromosome are remarkably normal. They behave almost identically to wild yeast cells, only they now possess new capabilities and can do things that wild yeast cannot.”

The scientists also removed the “junk DNA” from the chromosome, including base pairs known not to encode for any particular protein and “jumping gene” segments that randomly move around. They also altered other sets of base pairs to enable researchers to tag DNA as synthetic or native, and to delete or move genes around on the chromosome.

“When you change the genome you’re gambling. One wrong change can kill the cell,” says Boeke. “We have made over 50,000 changes to the DNA code in the chromosome and our yeast still live. That is remarkable. It shows that our synthetic chromosome is hardy, and it endows the yeast with new properties.”

Yeast shares about a third of its genes with humans, so this step in synthetic biology has big implications for what scientists could do one day with medicines.

“We can pull together any group of cards, shuffle the order and make millions and millions of different decks, all in one small tube of yeast,” Boeke says. “Now that we can shuffle the genomic deck, it will allow us to ask, can we make a deck of cards with a better hand for making yeast survive under any of a multitude of conditions, such as tolerating higher alcohol levels.”

Scientists could use the technique to quickly develop synthetic strains of yeast that could be used in the manufacturing of medicines like artemisinin for malaria. They could also use the techniques to help develop more efficient biofuels, like alcohol or butanol.

Boeke said the team’s success will lead to the contraction of other yeast chromosomes and move genetic research a step closer to constructing the organism’s entire functioning genome.