Individuals carrying a gene mutation are at an increased risk of developing neurological disorder related to touch and proprioception -- our "sixth sense" or body awareness -- a study has found.
The study was conducted on two young patients -- one nine and the other 19-years-old -- who were diagnosed with progressive scoliosis -- a unique neurological disorder in which a person's spine has a sideways curve.
The findings revealed that a gene called PIEZO2 that controls specific aspects of human touch and proprioception, is either directly required for the normal growth and alignment of the skeletal system or that touch and proprioception indirectly guide skeletal development.
"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," said Carsten G. Bonnemann from the National Institute of Neurological Disorders and Stroke (NINDS) -- a US based public research organisation.
The mutations in the PIEZO2 gene caused the two patients to have movement and balance problems as well as the loss of some forms of touch, the study said.
"Our results suggest they are touch-blind. The patient's version of Piezo2 protein may not work, so their neurons cannot detect touch or limb movements," added Alexander T. Chesler from National Center for Complementary and Integrative Health (NCCIH) -- a US based public scientific research agency.
Further examinations suggested that the patients also lacked body awareness. They could not feel vibrations from a buzzing tuning fork. Nor could they tell the difference between one or two small ends of a caliper pressed firmly against their palms.
Nevertheless, the patients could feel other forms of touch. They could feel the stroking or brushing of hairy skin.
However, one claimed it felt prickly instead of the pleasant sensation reported by unaffected volunteers.
Despite these differences, the patients' nervous systems appeared to be developing normally, the researchers said.
They were able to feel pain, itch, and temperature normally. The nerves in their limbs conducted electricity rapidly and their brains and cognitive abilities were similar to the control subjects of their age.
"What's remarkable about these patients is their nervous systems compensate for their lack of touch and body awareness," Bonnemann said.
The study suggests the nervous system may have several alternate pathways that we can tap into when designing new therapies.
Previous studies have showed that mutations in PIEZO2 may have various effects on the Piezo2 protein that may result in genetic musculoskeletal disorders, including distal arthrogryposis type 5, Gordon Syndrome, and Marden-Walker Syndrome, the researchers concluded in the paper, published in the New England Journal of Medicine.
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