Sixth Sense

It is beginning to appear as though human ave a sixth sense after all – but it has nothing to do with seeing ghosts, or into the future.

The sense is “proprioception,” and it describes the perception of movement and spatial orientation arising from stimuli within your body – the actual awareness of our body in space. In humans, these stimuli are detected by nerves within the body itself.

A new study suggests that a gene called PIEZO2 controls that sense. It was discovered when mutations in that gene were discerned as the cause of a unique neurological disorder in two young patients. The two had movement and balance disorders.

“Our study highlights the critical importance of PIEZO2 and the senses it controls in our daily lives,” said Carsten G. Bönnemann, MD, senior investigator at the National Institutes of Health’s National Institute of Neurological Disorders and Stroke (NINDS) and a co-leader of the study published in the New England Journal of Medicine. “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.”

PIEZO2 is a “mechanosensitive” protein -- it generates electrical nerve signals as a response to changes in cell shape. These changes include such as when skin cells and neurons of the hand are pressed against a table.

“As someone who studies Piezo2 in mice, working with these patients was humbling,” said Alexander T. Chesler, PhD, investigator at NIH’s National Center for Complementary and Integrative Health (NCCIH). “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.”

The patients' nervous systems were developing normally. All of the “regular” five senses operated as well as expected, and they were able to feel pain, temperature and itch. Their cognitive abilities were comparative to the control subjects of their age group.

As a result of their work in this study, Drs. Bönnemann and Chesler have a theory that PIEZO2 is either directly required for the normal growth and alignment of the skeletal system or that proprioception indirectly guides skeletal development. The next step for the researchers is to design experiments investigating the role of PIEZO2 in nervous system and musculoskeletal development.