Mind Over Mouse: Human Thoughts Control Gene Expression in Mice
What if there was a way to stop the agony of a migraine at the earliest stages, before you were even aware of the pain? Thanks to a pioneering approach that uses brain activity to remotely regulate gene expression in human cells, developed by Martin Fussenegger at Basel’s Swiss Federal Institute of Technology Zurich, such treatments to counteract pain and other pathological conditions at the first sign of a problem could one day become a reality, though not anytime soon.
In a report published November 11 in Nature Communications, Fussenegger and colleagues describe the creation of an optogenetic system that uses human brainwaves to drive gene expression in cell implants in nearby mice, resulting in production and secretion of a transgene protein into the animals’ bloodstream.
“This is a sophisticated fusion of current advanced research ideas into a powerful proof-of-concept device,” wrote Martyn Boutelle, Imperial College London, United Kingdom, in an email to PRF. Although still in the early stages of development, the new method suggests that “far into the future it may be possible for patients to learn to use mental states to control bioengineered implants that release relief-giving therapy,” he added.
Manipulating a gene…
The new method resulted from a variety of bits and pieces of technology “which we either carefully refined or designed de novo,” and were combined into the final product, explained Fussenegger.
“The central piece was the optogenetic device,” an implantable chamber containing human cells that responds to illumination of near-infrared (NIR) light, he said. First author Marc Folcher and colleagues constructed the device, a 2 cm by 1 cm plastic box that could be placed under the mouse’s skin. A transparent cultivation chamber in the device holds human cells expressing a light-responsive bacterial enzyme that dimerizes GTP to produce the bacterial second messenger cyclic diguanosine monophosphate (c-di-GMP). The cells were further “rewired” to respond to c-di-GMP by activating a synthetic promoter in the human secreted embryonic alkaline phosphatase (SEAP) gene, which produces a protein of no known function. “And so we could produce a protein directly in response to NIR illumination,” explained Fussenegger. Once made, the protein diffuses out of the device through a semi-permeable membrane and enters the mouse’s bloodstream.
“By engineering a cell construct using synthetic biology techniques, they have transferred this [optogenetic] ability from whole tissue to the isolated cells which they keep securely in an implantable chamber. The proteins that are made can get through the chamber membrane into the bloodstream, as can the nutrients required by the cells, but the cells themselves are held back,” wrote Boutelle.
In addition, unlike traditional optogenetic systems, which require an external light source, Fussenegger’s is entirely self-contained—the tiny implant also houses a NIR light.
…by harnessing human thought
In order to control their optogenetic device by human thought, the researchers used a low-cost electroencephalogram (EEG) headset to record brainwaves that were then processed by a computer. The computer output controlled a field generator, a device that can transmit energy wirelessly. Copper wire located inside the implant captured the electricity and used it to power the NIR light.
To generate the needed brainwaves, subjects were instructed to either focus and concentrate while playing the popular computer game Minesweeper, or relax and meditate while breathing deeply. Neither task required any training. In a third task, subjects were shown a live view of their EEG and instructed to increase or decrease the amplitude of the activity—a technique known as biofeedback. Six different subjects participated in the study, though Fussenegger noted that after the experiment, others in the lab also took turns trying out the system.
The three different mental states produce distinct patterns of brainwaves, said Fussenegger, each of which could be programmed to switch on the LED and control plasma SEAP levels in the mice. Actually, any activity that caused a shift in brainwaves could be used, he added.
To put it all together: when the participant’s brainwaves change, “the field generator transmits the electricity through the mouse body to the implant where the NIR LED is switched on. It illuminates the cells in the cell culture chamber and programs them to produce the protein, which is then secreted out of the cell and diffuses out of the implant … into the bloodstream of the animal,” Fussenegger said.
The mind-controlled transgene expression device consisted of (a) an EEG headset that captured brainwave activities (the encephalogram), identified mental state-specific electrical patterns (biofeedback, concentration, meditation), and processed discrete meditation-meter values (0-100; meditation-meter value plot), which were transmitted via Bluetooth to (b) the Arduino single-board microcontroller with a time-relay device and switching the (c) field generator ON and OFF. This brain-computer interface (BCI, a-c) controlled (d) the transmitter coil (c,d) of the field generator, which inductively coupled with the (d,e) receiver coil (RC) of the (e) wireless-powered optogenetic implant (e). The NIR light LED illuminated the culture chamber of the wireless-powered optogenetic implant and programmed the designer cells to produce SEAP, which diffused through the semi-permeable membrane. The blood SEAP levels of mice with subcutaneous wireless-powered optogenetic implants containing designer cells that were freely moving on the field generator could be modulated by the human subject’s mindset in a wireless, remote-controlled manner. Figure and legend courtesy of Nature Communications, Folcher et al., 2014.
Moving from mouse to human
The new technique is still a long way from moving into the clinic, but the hope is that someday, when pain is detected by a change in brainwaves, the device could be used to generate a compound that blocks or attenuates pain, instead of SEAP. An important advantage of the new device, which would be implanted locally under the skin, is that it could potentially treat pain automatically, as soon as the neural signal was detected, before the patient was even aware of any pain.
Similarly, the device could be used to treat a variety of other conditions such as epilepsy or neurodegenerative disorders. The device could also be used in a conscious fashion to help those with locked-in syndrome, a condition in which the patient is cognitively intact but cannot move due to paralysis of voluntary muscles.
Fussenegger noted that in order to best enable translation of the technology to humans, the researchers used as many human components as possible. For example, the cultivation chamber contained human embryonic kidney (HEK293T) cells, currently used in industry to produce drug targets and vaccines.
In order to get the device from mice into humans, researchers will need to develop a better understanding of a number of unknowns, he added, including whether the current production capacity of the cells, the size of the implant, and how any protein produced would be useful in humans. Fussenegger also says they will need to develop better algorithms to detect pre-pathological symptoms and then reliably convert them to a signal that the implant could recognize. “I think this can be done,” he said.
Fussenegger is currently talking to clinicians to learn to produce cells under good manufacturing practices (GMP), a strict protocol required for cells that would be put into patients, and working to set up a demonstration of the device in humans.
Allison Marin (Curley), PhD, is a neuroscientist-turned-science writer who resides in Pittsburgh, Pennsylvania, US.
Image: Nature Communications, Folcher et al., 2014
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