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

Jun 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: US scientists make embryonic stem cells from adult skin

add to favorites email to friend print save as pdf

Related Stories

Newly discovered virus linked to deadly skin cancer

Jan 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 associ ...

Mapping the neuron-behavior link in Rett Syndrome

Sep 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 ...

Rat hair cells found to be true stem cells

Oct 04, 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.

Suppressing cancer with a master control gene

Feb 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

Leeches help save woman's ear after pit bull mauling

Apr 18, 2014

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...

New pain relief targets discovered

Apr 17, 2014

Scientists have identified new pain relief targets that could be used to provide relief from chemotherapy-induced pain. BBSRC-funded researchers at King's College London made the discovery when researching ...

User comments : 0

More news stories

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Study says we're over the hill at 24

(Medical Xpress)—It's a hard pill to swallow, but if you're over 24 years of age you've already reached your peak in terms of your cognitive motor performance, according to a new Simon Fraser University study.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.