Reversible gene expression gets the blue light

Using blue light as the trigger, scientists have developed a laboratory technique to control where and when genes are expressed within cells.

The researchers behind the technology say that controlling gene expression in this way may help scientists to investigate the cause of diseases, to simulate disease states and even one day treat or regenerate damaged tissue.

Laura Polstein, first author on the paper presenting the technique and a graduate student at Duke University in the USA, said: 'We can now, with our method, make gene expression reversible, repeatable, tunable, and specific to different regions of a gene. Current methods of getting genes to express can achieve some of those characteristics, but not all at once'.

To demonstrate the spatial control of the gene expression system, the researchers created patterns - including polka dots and a smiley face - in cell cultures, photographs of which were published in the study.

The technique is called LITEZ, which stands for Light Induced Transcription using Engineered Zinc finger proteins. It uses proteins that allow the plant arabidopsis thaliana to sense the length of a day, in order to target gene expression.

In LITEZ, one light-sensitive protein is attached to an activator of gene expression whilst another is anchored to the gene of interest. When illuminated by blue light the two plant proteins move together, bringing the activator to the gene and triggering targeted gene expression.

Dr Jacqueline Matthews, a molecular biologist and associate professor at the University of Sydney, Australia, who was not involved in the study, told Cosmos magazine that the advantage of LITEZ over other gene expression systems was that 'it's quite reversible, so you can switch on gene expression and then switch it off'.

But Dr Matthews questioned whether LITEZ or similar technology could ever be used clinically: 'You've got to be able to get a light source onto this system and the cells need to have been spiked with LITEZ that targets genes. If you were dealing with cells in a culture it would be easy, but in many cases I don't know how you would get light on the right spots in actual people'.

However Professor Nicholas Dixon at the University of Wollongong, Australia, who was also not involved in the study, told Cosmos: 'In contrast to some other, more conventional methods, it does not require addition of chemical compounds that might have confounding effects - all that is required is to turn the light on and off'.

The study is published in the Journal of the American Chemical Society.