Link between light touch and Merkel cells solves 100-year mystery

June 18, 2009

Light touch - the sense that lets musicians find the right notes on a keyboard, a seamstress revel in the feel of cool silk, the artisan feel a curve in material and the blind read Braille - truly depends on the activity of Merkel cells usually found in crescent-shaped clusters in the skin, said researchers from Baylor College of Medicine and colleagues in a report that appears in the current issue of the journal Science.

"Human, primates and any animal that relies on hands for dexterity use their Merkel cells to feel texture and shape," said Dr. Ellen Lumpkin, assistant professor of neuroscience, molecular physiology and biophysics and molecular and human genetics at BCM and a senior author of the report. "Merkel cells are not like pain fibers. They exist in special areas of the skin to feel light touch. We have a lot of them on our fingertips and also on our lips."

However, while many scientists thought Merkel cells were key elements of light touch, they could never directly prove the link. The topic has been debated for more than 100 years, since the cell were first described in 1875 by German scientist Friedrich Sigmund Merkel (for whom they are named).

In cooperation with Dr. Huda Zoghbi (another senior author), Lumpkin, first author Dr. Stephen Maricich (now of Case Western Reserve University in Cleveland, Ohio), and colleagues generated mice that lacked a gene called Atoh1 in some areas of the body and, as a result, had no Merkel cells in skin located below the head. Experiments on these mice directly demonstrate the link between Merkel cells and touch in way that can be seen and heard.

That is probably the most significant thing about the paper, said Marichich. While Merkel himself first postulated the link between the cells and light touch, "this is the first direct evidence," said Maricich, who plans to continue working with the cells, determining the progenitor cells from which they arise and determining how they relate to human disease.

A decade ago, Zoghbi, Dr. Hugo Bellen and other BCM researchers identified Atoh1 (also called Math1), and were the first to show it affects hearing and proprioperception - the sensing of where parts of one's body are in space. (See figures 1 and 2)

Zoghbi is professor of pediatrics, molecular and human genetics, neurology and neuroscience at BCM and is also a Howard Hughes Medical Institute investigator.

"To our knowledge, Atoh1 is the first gene shown to be necessary for the specification of Merkel cells," the authors noted in their paper.

To further prove their point, the researchers used special equipment to record tiny electrical impulses that touch elicits from neurons in the skin. (See videos 1 and 2. Listen to audio recordings 1 and 2.) In mice that lacked Merkel cells, the skin was missing touch receptors with high spatial resolution (the hallmark of Merkel cells), but was still innervated by other touch-sensitive neurons.

While Merkel cells are probably not involved in proprioperception, Merkel cells and hair cells (the sensory cells of the ear) "allow you to manipulate objects with high spatial resolution and discrimination of sound. That's what I think is beautiful about Atoh1, the Merkel cell and the hair cell," said Lumpkin.

"These cells are the first way our body interacts with the outside world," she said. "Both hair cells and Merkel cells tell us what and when at the finest level we humans relate to our environment."

A decade ago, Lumpkin chose to study Merkel cells at the same time that Zoghbi and Bellen first announced their discovery that Atoh1 (Math1) is necessary for inner ear . She recognized that the two fields would someday have importance for one another.

Merkel cells are not limited to fingertips or lips, where tactile sensitivity is highest. They are also found in hairier parts of human skin as well as on the bodies of all vertebrates, from fish to primates.

In mice and other nocturnal animals, Merkel cells in the body might be important for maneuvering in the dark. Lumpkin and Maricich plan to use the mice lacking Merkel cells to directly test this possibility.

This is another important component of the Atoh1 network that helps people realize where they are in space, said Zoghbi. While the specific activity of Merkel cells permit light touch and the "what and when" of activity, "Atoh1-dependent neurons are processing that information," she said.

Lumpkin sees the finding as a stepping stone to even more basic answers.

"Bigger than that, we don't know how any mammalian touch receptor works," she said. "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."

Source: Baylor College of Medicine (news : web)

Explore further: Rat hair cells found to be true stem cells

Related Stories

Rat hair cells found to be true stem cells

October 4, 2005

Cells inside hair follicles are stem cells able to develop into the cell types needed for hair growth and follicle replacement, Swiss researchers claim.

Newly discovered virus linked to deadly skin cancer

January 17, 2008

A new strategy to hunt for human viruses described in this week’s issue of the journal Science by the husband-and-wife team who found the cause of Kaposi’s sarcoma has revealed a previously unknown virus strongly associated ...

Mapping the neuron-behavior link in Rett Syndrome

September 24, 2008

A link between certain behaviors and the lack of the protein associated with Rett Syndrome – a devastating autism spectrum disorder – demonstrates the importance of MeCP2 (the protein) and reveals never-before recognized ...

Suppressing cancer with a master control gene

February 23, 2009

Starting with the tiny fruit fly and then moving into mice and humans, researchers at VIB and K. U. Leuven show that expression of the same gene suppresses cancer in all three organisms. Reciprocally, switching off the gene ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Machine Translates Thoughts into Speech in Real Time

December 21, 2009

( -- By implanting an electrode into the brain of a person with locked-in syndrome, scientists have demonstrated how to wirelessly transmit neural signals to a speech synthesizer. The "thought-to-speech" process ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.