Medical Center Researcher Explores What Happens When We Touch
Some four million touch receptors cover the human body, with the skin also serving as a protective barrier from germs as well as keeping water in and the body hydrated.
The breadth of this most complicated of the senses is so sweeping that when Ellen Lumpkin entered the field in 1998, “our understanding of touch was easily three to six decades behind our understanding of the other senses,” she said.
Lumpkin is an associate professor in the departments of physiology and cellular biophysics as well as dermatology, but her Ph.D. is in neuroscience. Her research group examines how the skin’s sensory neurons distinguish among the countless tactile sensations encountered every day.
“Why do some objects feel soft, and others feel firm? How can we detect shapes, edges and textures?” she said. Her lab explores those questions at the molecular and cellular level using a variety of tools including genetically modified mice and live cell imaging, a technique that uses time lapse microscopy. “We are particularly interested in how skin cells communicate with the nervous system to encode touch.”
Her research into one particular type of skin cell—called the Merkel cell, which she believed was a touch receptor—has resulted in a series of scientific discoveries that have upended conventional wisdom and rewritten textbooks.
“We knew these cells and their neighboring neurons form very special receptors important for the sense of fine touch,” she said. “But where did the signals for them originate? We had to know that before we could figure out how.”
Lumpkin’s interest in science began as a child in East Texas, where she was a member of Future Farmers of America. In ninth grade she learned about genetics in a class on animal breeding, and “that’s when I decided to be a scientist,” she said.
As a Ph.D. student in the mid-1990s at the University of Texas Southwestern, Lumpkin initially focused on hearing, examining the tiny cells in the inner ear that allow us to interpret the sounds around us. But once she began working as a postdoctoral fellow at the University of Washington, she turned her attention to touch, motivated by how little was known about that function in mammals.
Searching for a starting point, Lumpkin came across the extremely rare Merkel cell. It was discovered in 1875 in a pig’s snout by Friedrich Merkel, a German scientist who believed it was a direct connection to nerves and thus was a “touch” cell—a hypothesis that was debated in the scientific community for decades.
Lumpkin has expertise in somatosensory biology—which refers to sensations that occur anywhere in the body, as opposed to location-specific sight or taste. She spent hours in her lab literally pushing on cells to see how they convert physical sensation into an electrical signal to the nervous system, determined to settle the century-old mystery.
Then, in 2004, she and her group at University of California, San Francisco, published a paper showing that Merkel cells are armed to send touch signals to our nervous system. Merkel’s 1875 hypothesis had been spot-on.
In a 2014 study published in Nature, Lumpkin teamed up with colleagues at Scripps Research Institute in La Jolla, Calif., to uncover just how the Merkel cells achieve their touch function. They identified a little-known cell protein called Piezo2, which is necessary for Merkel cells to produce the prolonged firing pattern that allows us to distinguish shapes and edges.
“Our big ‘aha’ moment was that both the neuron and the Merkel cell are sensors that must work together to send this particular touch signal,” said Lumpkin. “They both use the same molecular force sensor—Piezo2—to convert touch into an electrical signal.”
Lumpkin’s work in touch receptors could be applied to solutions involving the placement of sensors in prosthetics, or to help restore touch sensation via stem-cell technology, work that is being spearheaded by David Owens, an associate professor of dermatology at Columbia University Medical Center.
“My job as a principal investigator is to set a tone where crazy ideas are appreciated and allowed to foster, but in a rigorous way,” Lumpkin said. “For me, the most important aspect of success in science is the people in my group who are in the lab every day, excited about new knowledge and bringing their different perspectives to the work.”