You may remember the picture of a star-nosed mole that I included in a previous newsletter. To jog your memory, it was a small furry creature about the size of a hamster. It had the body shape of a seal, the fat paws and long claws of a sloth and in place of a normal-looking head, it had a star-shaped appendage on its snout. The mole's star organ, which is smaller than a fingernail, is innervated 10 times more than the whole human hand and allows it to feel textures and vibrations of tiny insects underground that its foraging competitors can't detect. Last month, I met with Diana Bautista, an associate professor of cell and developmental biology at U.C. Berkeley, who spends a lot of time studying these animals. For a scientist specializing in understanding the molecular basis of touch, they're the ideal study organism.
I visited Bautista so she could explain touch to me at a cellular level, from skin to brain. She told me what she knows, which I write about in my book, but there's also plenty that isn't known. It turns out that the process of sensory transduction for touch, or how pressure on our skin gets converted into an electrical signal that reaches our brain, is quite mysterious. Our understanding of touch lags behind the other senses, something that Bautista is trying to rectify. To put this into historical context, scientists discovered about 130 years ago that vertebrates have a protein in their eyes called rhodopsin, which changes shape when it is bombarded with light and triggers a channel of events that convert it into electrical signals. And the transduction channels for our sense of smell were discovered in the 1990s. Only in the last few years did scientists discover a channel responsible for light touch sensations. But there are so many others that remain undiscovered, such as those for itch and pain and vibration.
Bautista's studies of the star-nosed mole aim to discover more of these channels. She described for me how she conducts her research. In the springtime, Bautista and her colleague Kenneth Catania, a MacArthur genius and professor at Vanderbilt University, get hunting licenses to collect specimens in a state forest in northern Pennsylvania. They hike in muck boots along creeks searching for signs of mole tunnels. As they find holes in the ground, they set off hundreds of Havahart mousetraps, which lock up the animals live. Moles eat around the clock, and they would starve to death without food for a few hours, so Bautista and Catania have to check the traps around the clock and also let out any other animals they happen to catch, such as weasels and snakes. They spend about five days doing this. In a good year, they might catch 20 moles this way.
Once she has them back at her lab, Bautista tests the moles to see which molecules are expressed at a higher level in the star organ than in the rest of its body. That way, she has a good idea of which ones might make good candidates for touch research. Then, she and her research partners identify the genes that encode these sensors. Some of these genes correspond with ones found in mice, and also humans. Once the group identifies the genes they want to study, they silence them in test mice to see how their abilities to detect touch and pain are altered. Bautista is still in the midst of this research, but she hopes to finish in two years. By that time, she hopes to add to our current, slim library of touch transduction channels.
Bautista believes that one of the reasons for the lack of touch research is that we don't realize how important it is. But in fact, touch is responsible for so many things that we do daily and often take for granted. That's definitely a lesson I've learned through the course of the research for my book. And I'd never really thought about it before, but Bautista explained to me that altered tactile sensitivity is one of the most common complaints from a clinical perspective, from diabetes numbness to peripheral nerve damage to chronic pain. Meeting with Diana, and learning about the current state of our understanding of touch, was fascinating. I hope to join her this spring when she and Catania go on their annual mole-hunting trip.
Thanks for reading!