'Artificial cell' can make its own genes

An "artificial cell" capable of synthesising genes and making them into proteins has been developed by researchers in the US.

Cells are governed by genes which provide instructions for making proteins that carry out the cell's functions.

The postage stamp-sized machine able to make and express its own genes offers a fast and cheap new way of making "designer" proteins not found in nature. It could ultimately help scientists test how individual patients will react to specific drugs.

"At very small volumes in the order of tens of nanolitres, we can construct completely synthetic genes and express these genes to yield functional protein," David Kong of Massachusetts Institute of Technology (MIT), Boston, US, told New Scientist.

The artificial cell resembles a computer chip. It is made from layers of rubber, forming a solid chip shot through with a network of tiny passages and chambers.

"This rubber has lines and features that are the size we need for our microfluidic chambers, channels and valves," says Peter Carr, who was also involved with the work. "With a few layers of this rubber, put together carefully, you can build a fairly complex device."

Shining example

After building separate gene synthesis and protein expressions chips, the researchers have now successfully integrated the two into a single system.

The first part of the device synthesises the genes using enzymes to join together DNA strands from a pool of short templates. The finished genes are then copied to produce many versions of the final product. Cycles of heating and cooling control the enzymes carrying out the reactions.

Once the genes have been made, a series of tiny pumps mixes them with the enzymes and cell extracts needed to make proteins.

First, a set of enzymes must convert the DNA of the genes into RNA. This RNA is then mixed with extracts from bacterial cells containing amino acids from which proteins are made, and ribosomes, the cell structures that "read" RNA and assemble the amino acids into finished protein.

In test runs, the artificial cell was used to make a fluorescent protein from jellyfish. Other proteins can also be designed with a fluorescent portion. "We can see very clearly that we have functional glowing protein, so we know it works," says Kong.

Cancer simulation

Kong believes his new device will be valuable for researchers investigating novel protein designs. The team is now exploring ways to make much larger devices containing thousands of reaction chambers that can synthesis many different proteins at once.

The diminutive devices shrink the cost as well as the size of the protein design process, says Kong, because smaller amounts of expensive reagents are needed. "You can do 100,000 experiments for the price that people can normally do 50 experiments," he adds.

Carr hopes that in the future such devices will be complex enough for use in cancer treatment. "I could start with the genetic information from a patient, program it into the device that we are working on, and essentially run a kind of simulation of how a drug might affect their cancer,” he explains.

Other groups have shown that proteins can be expressed in artificial conditions, but the new device has taken the idea of an artificial cell one step closer to reality, says Hugh Fan of the University of Florida, Gainesville, US, who was not involved in the study.

"This group has advanced the field by showing the integration of gene synthesis with protein expression in one device,” he told New Scientist.

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