Mutations found in the gene PIEZO2 have led researchers from the National Institutes of Health to conclude that a sixth sense may be possible in humans.
The patients these mutations were discovered in—a 9-year-old girl and a 19-year-old woman—were brought together to monitor after it was found that they displayed similar deformities and sensory problems.
According to the New England Journal of Medicine, where the study was published, both patients had balance issues, trouble walking and deformities in their hands, hips and feet. They also had abnormally curved spines that were originally diagnosed as progressive scoliosis.
Dr. Carsten Bonnemann, a pediatric neurologist at NIH’s National Institute of Neurological Disorders and Stroke, worked with Dr. Alexander Chesler, a researcher at NIH’s National Center for Complementary and Integrative Health, to study the patients and their mutations in their PIEZO2 gene. The gene mutations have previously been found to be prenatally fatal in mice. For the two patients, however, it only left them with their deformities and a unique lack of spatial awareness.
The patients were tested for bodily awareness and sensitivity to touch, having their data compared to control groups consisting of people without their disorders. In one test, the patients were blindfolded and asked to touch an object in front of their faces. This task proved to be extremely difficult since the patients did not seem to know which direction their arms were moving in without sight. In another sensory test, the two females were unable to feel the vibrations of a tuning fork—a device that vibrates a specific pitch when struck—as well as the control subjects could. Similarly, when the two patients were blindfolded, they were unable to walk properly, stumbling and falling frequently.
The patients, however, were able to feel, just not as acutely as is considered normal. When a brush was passed over hairy parts of their skin, both patients felt it, but one of them reported feeling a prickly sensation, whereas unaffected volunteers normally report it as a pleasant sensation.
Bonneman and Chesler repeated the sensory tests with the patients strapped into MRI machines. They found that the brush, which should have activated a part of the brain linked to physical sensation, was producing brain activity in a region of the brain associated with the emotional response to touch. The conclusion was that both of the patients could not physically feel the brush and were experiencing something similar to an emotional response to its touch.
The last set of tests involved the patients holding a device that progressively became hot or cold. To the researchers’ surprise, both patients were able to perceive changes in temperature and could feel the pain.
The results of these tests led Chesler and Bonnemann to conclude that the PIEZO2 gene played a key role in the sensation of touch and proprioception—the sense of one’s relative position of body parts and strength involved in moving—but did not play a role in sensations of temperature or pain. Bonneman was impressed by the the bodies’ compensation for the deformities.
“What’s remarkable about these patients is how much their nervous systems compensate for their lack of touch and body awareness,” said Bonnemann. “It suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies.”
The findings of this study suggest that PIEZO2 may have a direct role in skeletal development, or that proprioception is necessary for proper skeletal development. Despite the mutations, the nervous systems of both patients appeared to be developing normally; they were capable of feeling temperature, itch and pain. Results from this study will later be used to investigate the role of PIEZO2 in nervous system and musculoskeletal development.
According to Bonnemann, understanding the data from both patients may provide clues to a variety of neurological disorders. Alternatively, the researchers speculated that variations in the gene may explain why a person is uncoordinated or clumsy.
For both patients, a sixth sense could be present in theory, but it is not what is typically regarded as a sense. Unlike more immediately apparent senses, such as taste and sight, this sense would simply be the human body’s ability to feel location in space and move accordingly.