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Merkel Cells Linked to Light-Touch Sensation

Scientists have demonstrated that the sensation of light touch, such as that which allows one to feel the fine texture of materials or lets the blind read Braille, depends on the activity of the long-mysterious Merkel cells, which are present in high numbers on our fingertips and lips. These cells form complexes with nerve fibers, and while these complexes are known to respond to light touches to the skin, the specific role of the Merkel cells has been controversial. The topic has been debated for more than 100 years, since the cells were first described in 1875 by German scientist Friedrich Merkel, who himself first proposed the link with light-touch sensation. The key to the current conclusive demonstration of the link was work with a transcription factor gene called Atoh1. When this gene was conditionally knocked out in the body skin and foot pads of mice, the resulting knockouts had no Merkel cells in these areas. The skin of these knockout mice did not show the same neurological responses to light touch that normal skin does, suggesting that Merkel cells enable their connecting neurons to resolve fine spatial details, the authors reported. "To our knowledge, Atoh1 is the first gene shown to be necessary for the specification of Merkel cells," the authors noted. "We don't know how any mammalian touch receptor works," added Dr. Ellen Lumpkin, of the Baylor College of Medicine, and a senior author on the report. "What genes allow them to function as light or painful touch receptors? This project gives us the experimental handle with which to start to dissect the genetic basis of touch." Among the other authors on the report were Dr. Huda Zoghbi and Dr. Stephen Maricich. This work was reported in the June 19 issue of Science. [Press release]