Moving in the "Sixth Sense"
March 29, 2006
ANN ARBOR, Mich---One of our first science lessons included learning the five senses: touch, sight, smell, hearing and taste. The "sixth sense," not the E.S.P. kind, but the kind that researchers study, is called proprioception. Proprioception allows you to touch your nose with your eyes closed. It is the sense of where your body is in space. Proprioception helps you balance and how to put one foot in front of the other to walk without looking at your feet.
Scientists at the University of Michigan have made insights into proprioception by discovering a gene encoding an ion channel protein that regulates "stretch receptors," which are cells responsible for mediating proprioception. For patients with Parkinson's disease, these stretch receptors have been implicated in the loss of movement control, so finding a gene that regulates the signals coming from stretch receptors is a step towards developing treatments.
Shawn Xu, Life Sciences Institute research assistant professor and assistant professor of Physiology at UM Medical School, and his colleagues discovered that the "sixth sense" is present in the nematode C. elegans. Because C. elegans is a simple genetic model organism, they were able to dissect in detail how these animals employ proprioception to guide muscle movement. They identified a critical ion channel protein, TRP (pronounced trip), that acts in the stretch receptor to guide muscle movement. As TRP channel proteins are also found in humans, this suggests that related human proteins may carry the same function in humans. Of equal importance, the worm stretch receptor the Xu team identified is functionally analogous to human muscle spindles and Golgi tendon organs, the two critical types of stretch receptors that regulate muscle movement in humans.
"It appears that some of the basic principles underlying sensory regulation of motor activity are evolutionally conserved from worms to human," Xu said. "Thus, C. elegans promises a valuable genetic model for studying proprioception and its related human diseases."
The paper "A C. elegans stretch receptor neuron revealed by a mechanosensitive TRP channel homologue," by Wei Li, Zhaoyang Feng, Paul W. Sternberg, and X. Z. Shawn Xu, was published in the journal Nature, March 30, 2006.
Xu has won accolades for young researchers, including a Harold Weintraub Graduate Student Award and Helen Hay Whitney Foundation Fellowship and most recently the Sloan Research Fellowship.
