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"Is it getting hot in here, or is it just me?" That's what a fly under the effects of the "Fly Mind-Altering Device" might say as the neural circuits involved in mating are activated — by heat generated from a beam of infrared light. It's a futuristic take on an established technique.
Thermogenetics is a field in which cells in animals are made to grow certain proteins customized to react to heat. For instance: Put some thermally reactive molecules in neurons related to a fly's hunger center, and as the temperature rises, so does the fly's appetite. Put those molecules in the part of the fly's brain that initiates mating, turn up the thermostat, and watch things heat up, so to speak.
But waiting for the ambient temperature to warm a fly sufficiently for an experiment can be a tedious process when you need to do it over and over. Researchers at the Howard Hughes Medical Institute has come up with a faster — and much more exciting-sounding — method of putting flies in the mood.
The researchers found that strains of flies with the heat-sensitive protein, in this case one called TRPA1, can be heated up individually with an infrared laser. A camera tracked the captive fly in its box, and the inactive laser was kept trained on it. When the beam was turned on, the fly instantly began courting the nearest object — even a ball of wax — and continued to do so for 15 minutes after the beam was turned off.
Another test had TRPA1 baked into certain muscle coordination centers; blasting these flies with infrared light caused them to walk backwards, stopping as soon as the IR bombardment did.
The technique makes experimentation with genetically modified flies quicker and easier. Barry Dickson, a neuroscientist at HHMI's Janelia Farm Research Campus, has submitted a paper describing the technique to an unnamed journal for publication. Dickson is cited in Nature's report as an author of the work, but in a comment he credits several others: Dan Bath, John Stowers, Dorothea Hörmann and Andrew Straw.