When activated in this way, the ion channels open to allow an inflow of sodium or other positively charged ions. Such a surge of electrical charge into a nerve can initiate a signal that travels up the nerve and to the brain via a relay of neurons along the spine.
In the earlier study, Patapoutian's team found evidence that Piezo2 proteins are made within touch-sensing neurons, including gentle-touch neurons that extend their nerves into the skin and against the mysterious Merkel cells.
In the new study, Patapoutian and his colleagues set out to learn more.
In Pursuit of Answers
The team began by creating a line of mice in which the activity of the Piezo2 gene also causes the production of a fluorescing protein called GFP. Guided by these fluorescent beacons as well as other markers, they found a high concentration of Piezo2 in Merkel cells in the skin of the mice.
"You can easily miss Piezo2 expression in the skin, because it's not highly expressed there, aside from the tiny population of Merkel cells," said first author Seung-Hyun Woo, a postdoctoral fellow in the Patapoutian laboratory.
Next the researchers sought proof of Piezo2's role in Merkel cells, essentially by subtracting the protein from those cells and observing the result. To do thisa particularly challenging featthey created a new line of mice in which the Piezo2 gene is specifically "knocked out" of all skin cells, including Merkel cells, but left intact everywhere else where it is ordinarily produced.
Piezo2 skin-knockout mice and their Merkel cells appeared normal. The mice also responded normally on most standard tests of touch and pain sensitivity. But on the so-called von Frey test, in which thin, bendable fibers are pressed against the mice's paws with varying force, the e
|Contact: Mika Ono|
Scripps Research Institute