From a faint breeze on the back of the neck to a mosquito that alights on the arm, the body has a remarkable ability to detect even the slightest touch. Scientists have uncovered much about the physiological and anatomical mechanisms of this sense, but the details of how it works on a molecular level have remained largely unknown. Part of the difficulty stems from the fact that the nerve endings in question are extremely small. The findings of a study published today in the journal Nature, however, offer new insight. According to the report, researchers have identified a protein, known as BNC1, that appears to play an important role in a mammals ability to sense light touch.
Michael J. Welsh of the University of Iowa and his colleagues decided to investigate BNC1 because it is the mammalian version of a protein belonging to a group of so-called ion channel proteins associated with touch-sensing in the roundworm Caenorhabditis elegans. Specifically, they studied the effects of deleting the BNC1 gene, which makes the protein, from a line of genetically engineered mice by comparing them with normal mice. Knocking out BNC1 resulted in mice that were greatly impaired in their ability to detect light touch. Without BNC1, the receptors that surround an animals hair follicles malfunction, failing to trigger the nerve impulse that tells the brain that the hair has been moved. Yet because they did not lose that ability altogether, Welsh remarks, "We postulate that the BNC1 channel may be one component of a larger receptor complex. In the absence of BNC1, other components of the channel may retain sufficient function for some residual sense of light touch." The location of the BNC1 protein also hints at its role. "We found the protein located in fibers that surround the hair shaft like a picket fence," he observes, "so when a shaft of hair bends in any direction, these fibers are deflected."
"I think this is an important first step toward understanding this elusive sense of touch," Welsh asserts. "Now we need to look at other members of this family of ion channel proteins, as well as the proteins that associate with these channels."