As senses go, touch might be the least understood. While touch-associated maladies do exist, we don’t often read about sufferers from them. A team of researchers at the Scripps Research Institute spent decades looking into how organisms perceive changes in temperature and pressure. After discovering ion channels ( i.e., fast-signaling proteins) that respond to changes in temperature, they began searching for similar channels for changes in pressure. In 2010, the work led them to the identification of two pressure-sensing proteins, PIEZO1 and PIEZO2, the name coming from the Greek word for pressure. The scientists thought, at the very least, more focused study of the proteins, and how genes express them in various tissues, would lead to better understanding of organ physiology and, of course, pain management. A recent study, however, has shown these proteins might be responsible for far more. They may hold the key for why some people have more difficulty orienting themselves in space, what is known as “Sixth Sense” of proprioception. Those who lack proprioception have difficulty navigating without sight.
Scientists at the National Institute of Health (NIH) discovered the link while examining two patients suffering from a variety of health issues including deformities in their fingers and feet and curvature of the spine. Both had difficulty walking and showed an extreme lack of coordination. While the patients also reported peculiarities with their sense of touch, they could sense pain normally and showed normal strength. The scientists subjected them to a series of tests, including brain scans and a full genetic screening. The scans showed nothing out of the ordinary, but the genetic screening did uncover that both shared a mutation in the piezo2 gene. What was shocking about this was that previous attempts to suppress the gene in mice had resulted in death. Why wasn’t a mutation in humans fatal as well?
Lead researcher Dr. Carsten G. Bönnemann and his team began testing the patients against a group of volunteers whose genome did not show the PIEZO2 mutation. When blindfolded, the volunteers could walk normally and perform simple tasks like touch a finger to their noses, a common test police officers use to determine if a driver is impaired. The affected patients could not, nor could they even distinguish, in which direction one of their limbs was being moved. Technically speaking, they lacked proprioception. With their eyes open, however, they could perform normally. Physiologically-speaking their nervous systems also appeared to be operating normally.
“What’s remarkable about these patients is how much their nervous systems compensate for their lack of touch and body awareness. It suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies,” Dr.Bönnemann said in a report about the research.
Two patients, of course, do make compelling results for a study, but now that the mutation has been identified, the NIH team believes they will uncover more who suffer from it.
Think about all the movements you make without “looking” at what you’re doing. Touch typing or walking across a dark room is next to impossible for those who lack proprioception. Equally intriguing is how the PIEZO2 mutation might relate to the skeletal deformities both patients experienced. Might it also play an as-yet-unknown role in skeletal development? Or, possibly, might the lack of proprioception those with the mutation experience cause them, from a young age, not to hold a correct posture and so inhibit the skeletal structure from developing properly?
According to Ardem Patapoutian, one of the original Scripps researchers who identified the proteins, “I think these claims are provocative but indeed possible. An indirect role of touch or proprioception in bone formation is an intriguing and exciting possibility.”
Even more intriguing, and more relevant to most, is the idea that perhaps there are variations in the mutation that are more common. Perhaps, PIEZO2 could explain why some people are clumsier than others, or even why some are superior athletes.
More to Explore
Piezo1 And Piezo2 Proteins Involved In Cellular Response To Mechanical Stimulation
The Role of PIEZO2 in Human Mechanosensation
How A ‘Sixth Sense’ Helps Simone Biles Fly, And The Rest Of Us Walk
Unraveling a genetic clue to our “sixth sense”