There is actually a "sixth sense" that goes beyond the five tangible ones that we've always taken for granted. And this sense is due to a gene that has a special name: PIEZO2.
The gene impacts proprioception, responsible for the manner in which the brain can understand the position of the body in space, explain researchers from the U.S. National Institutes of Health (NIH). Patients who have mutations in the PIEZO2 tend to lose their "sixth sense."
Researchers made the discovery by examining two young patients who showed PIEZO2 mutations, which led to some flaws in balance and movement, along with the loss of a few forms of touch.
"Our study highlights the critical importance of PIEZO2 and the senses it controls in our daily lives," said study leader Dr. Carsten G. Bönnemann, senior investigator at the NIH's National Institute of Neurological Disorders and Stroke.
"The results establish that PIEZO2 is a touch and proprioception gene in humans. Understanding its role in these senses may provide clues to a variety of neurological disorders," added Bönnemann.
Scientists studied the two patients who were of different ages. One was 9, while the other was 19 years old. They were unrelated, but they both had problems walking. They were also discovered to show some foot, hip and finger deformities. They were also diagnosed to have progressive scoliosis.
As proteins are needed for the development of the skeletal system, the lack of these proteins might lead to some scoliosis and joint problems too.
There are other surprising and worrisome body movements in both. When the two were blindfolded, they found it difficult to walk, stumbling and staggering from side to side. They had to be held by assistants to keep them from keening over.
Two unaffected volunteers did not find it so difficult to locate an object in front of them as the two patients did. The volunteers could also guess the manner in which their joints were being moved, while the patients could not.
The young patients also showed less sensitivity to certain forms of touch. They could not sense the vibrations made by a buzzing tuning fork and could not differentiate between one or two ends of a caliper when it was pressed on their palms. One patient's brain scans did not register a response when her palm was brushed.
The patients could feel other touch-based sensations however, such as the brushing of hairy skin, but one patient described the sensation to be "prickly" in contrast to the "pleasant" feeling reported by unaffected volunteers.
Still, researchers did not find any developmental problems in the nervous systems of both patients. Sensations of pain, itching and temperature were felt normally, their nerves conducted electricity rapidly plus their brain and cognitive abilities were equivalent to those of the control subjects.
"What's remarkable about these patients is how much their nervous systems compensate for their lack of touch and body awareness," said Bönnemann. "It suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies."
The discovery was published in the New England Journal of Medicine.