Researchers develop new caffeine-responsive “genetic switch”

Scientists from the Engineering Biology for Advanced Therapeutics Hub have contributed to research led by the Technical University of Darmstadt, developing a caffeine-responsive “genetic switch”. The work, published in Nucleic Acids Research, addresses a key challenge facing the field: finding and testing genetic switches that work well in human and mammalian cells.

A central goal of engineering biology is being able to control exactly when and how a gene is switched on or off inside a living cell, which holds great potential for the development of new therapies.

One promising tool is the aptazyme, a genetic control system made of two parts: a sensor called an aptamer that recognizes a specific molecule, and a switch mechanism that can ramp gene expression up or down. This makes aptazymes useful as “molecular on/off switches” for controlling genes with a chosen chemical.

However, there are limited well-performing aptamers, and many are less effective in mammalian cells. Identifying and validating new aptamers and aptazymes is difficult because it requires testing a large number of candidates, and screening at scale has remained slow.

Leon Kraus and Vincent Gunawan (Beatrix Suess Lab, Technical University of Darmstadt) first identified a brand-new aptamer that responds to caffeine, a convenient, well-characterised substance. Working with colleagues from the Hub, they engineered it into an aptazyme which responded to the presence of caffeine by triggering production of a green fluorescent protein, allowing them to see the switch working in real time. 

The Hub’s contribution included the development of a mammalian cell screening platform by Adam Mol (Susan Rosser Lab), built on the Beacon® optofluidic system at the Edinburgh Genome Foundry. The Beacon® uses light to push single cells into tiny pens so they can be individually monitored, allowing different versions of the caffeine-responsive aptazyme to be introduced into cells and tracked over several days. By recording fluorescence changes across more than a thousand individual cells, researchers could identify those carrying the most effective genetic switches. This new screening platform provides a scalable way to test many aptazyme designs in mammalian cells at once, a barrier that has previously slowed progress in this area of research.

This work not only introduces a new caffeine-responsive genetic switch with many exciting future applications, but also establishes a faster screening method for mammalian cells that could speed up the discovery of new genetic switches responsive to specific drugs or disease signals within the body. This could pave the way for safer and more controllable gene-based therapies.