‘Sixth Sense’ of Spatial Awareness is Genetic

     (CN) — The sublime acrobatic ability of gold medal-winning gymnast Simone Biles and other top athletes might stem from a gene that gives them a stronger “sixth sense” of where their bodies are in space.
     In a study published Wednesday, researchers from the National Institutes of Health suggest that a gene called PIEZO2 controls specific aspects of human touch and movement, which enables gymnasts and dancers to understand their bodies’ exact positioning at a given time, including the amount of force each muscle is exerting.
     The study analyzes a rare genetic disorder that affects proprioception, the “sixth sense” that produces awareness of one’s body in space, which requires those affected to rely heavily on vision and other senses.
     “Our study highlights the critical importance of PIEZO2 and the senses it controls in our daily lives,” said Carsten Bonnemann, 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.”
     The team studied two patients, one age 9 and the other 19, who have trouble walking and suffer from hip, finger and foot deformities, as well as abnormally curved spines diagnosed as progressive scoliosis.
     Researchers discovered that the patients have mutations in the PIEZO2 gene that seems to block the normal production or activity of PIEZO2 proteins in their cells.
     “As someone who studies PIEZO2 in mice, working with these patients was humbling,” study co-author Alexander Chesler said. “Our results suggest they are touch-blind. The patient’s version of PIEZO2 may not work, so their neurons cannot detect touch or limb movements.”
     PIEZO2 has a mechanosensitive protein because it generates electrical nerve signals in response to changes in cell shape, such as when skin cells and neurons of the hand are pressed against an object. Studies in mice suggest the PIEZO2 protein is found in the neurons that control proprioception and touch.
     Additional examinations indicated that the patients lack body awareness. Blindfolding them made walking very difficult, causing them to stumble from side to side as assistants prevented them from falling. When the team compared the two patients with unaffected volunteers, they found that blindfolding the patients made it harder for them to reach for an object in front of their faces than it was for the volunteers.
     The researchers also found that the patients were less sensitive to touch. They could not feel vibrations from a buzzing tuning fork as well as the control subjects, nor could they tell the difference between one or two small ends of a caliper pressed firmly against their palms. Brain scans of one patient showed no neurological response when the palm of her hand was brushed.
     However, the patients could feel other forms of touch. Stroking or brushing hairy skin is generally perceived as pleasant, but one claimed the contact felt prickly. Brains scans showed different activity patterns in response to brushing between the volunteers and the patient who felt prickliness.
     Despite these differences, the patients’ nervous systems seemed to be developing normally. They were able to feel pain, itch and temperature normally, and their brains and cognitive abilities were similar to the control subjects of their age.
     “What’s remarkable about these patients is how much their nervous systems compensate for their lack of touch and body awareness,” Bonnemann said. “It suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies.”

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