2009-ASCB-Press-Book - page 9

T h e A m e r i c a n s o c i e t y f o r C e l l B i o l o g y
7
News from
The American Society
for Cell Biology
49th Annual Meeting
San Diego, CA
December 5–9, 2009
Light touch, fingered at last
EMBARGOED
FOR RELEASE
10:00 am, U.S. Pacific Time
Tuesday, December 8, 2009
After more than a century,
a knockout mouse lacking
mysterious Merkel cells finally
unlocks the secret of light touch
T
he mystery is at your fingertips.
Biologists have long suspected that
the sensation of light touch was
made possible by Merkel cells, discov-
ered in 1875 by the German anatomist
Friedrich Merkel. But the cells have
remained enigmatic, largely because it
proved impossible to show experimen-
tally that Merkel cells were anything more
than “associated” with light touch. Ellen
Lumpkin and colleagues at the Baylor
College of Medicine and elsewhere have
now provided answers to the key ques-
tions swirling around Merkel cells for so
long: Are Merkel cells directly activated
by touch? Is touch reception compro-
mised in animals that lack Merkel cells?
First, the Lumpkin lab studied nor-
mal mice by isolating Merkel cells and
by recording neural impulses from touch
receptors in the skin. By applying force
to isolated Merkel cells, the researchers
showed that these cells were inherently
touch sensitive. They also identified
genes that allowed Merkel cells to con-
vey neural signals to sensory neurons.
This evidence suggested that Merkel cells
could serve as touch receptor cells but
didn’t prove it. The newly identified genes,
though, hinted at the basis of light touch.
The Lumpkin lab then turned to mice
they had generated that lack Merkel cells
in their bodies. The researchers measured
the responses of all classes of touch re-
ceptors that innervated the mouse skin.
“Although we saw no changes in touch
receptors that respond to noxious (or
painful) touch, we observed a complete
loss of a particular type of light-touch
receptor,” Lumpkin reports. “These re-
sults demonstrate that Merkel cells are
required for appropriate sensory coding
of light touch.”
These results go beyond supplying
the proof to a 134-year-old hypothesis,
says Lumpkin. “The sense of touch pro-
vides a constant stream of information
to our brains about the objects that sur-
round us. For example, touch receptors in
our hands allow us to recognize shapes,
feel textures, and grasp objects with high
fidelity. Thus, touch is critical for our
hand dexterity. It enables countless daily
tasks ranging from the mundane, such as
typing an email, to the essential, such as
drinking a glass of water.”
Merkel cells (green, left panel) have long been proposed as mechanosensory cells that transduce touch and then
activate sensory neurons (red). Merkel cells cluster in highly touch-sensitive skin areas, where they are innervated
by a branching sensory neuron (middle panel). To test their hypothesis, Lumpkin and colleagues made transgenic
mice that lack Merkel cells but retain sensory innervation (right panel). These mice completely lack the touch
responses that are characteristic of Merkel cell-neurite complexes.
Contact
Ellen A. Lumpkin
Baylor College of Medicine
One Baylor Plaza
Houston, TX 77030
(713) 798-3418
Author presents
Tuesday, December 8, 2009
9:35–9:55 am
Minisymposium 18: Cell and
Tissue Mechanics
Program 1582
Ballroom 20B–C
Mechanotransduction in the
Merkel Cell–Neurite Complex,
a Conserved Vertebrate Touch
Receptor
E. Lumpkin, H. Haeberle, S.
Wellnitz, A.M. Nelson, H. Zoghbi
Neuroscience, Baylor College of
Medicine, Houston, TX
E. Lumpkin
Molecular Physiology and
Biophysics, Baylor College of
Medicine, Houston, TX
E. Lumpkin, H. Zoghbi
Molecular and Human Genetics,
Baylor College of Medicine,
Houston, TX
S. Maricich, H. Zoghbi
Pediatrics, Baylor College of
Medicine, Houston, TX
D. Lesniak, G. Gerling
Systems and Information
Engineering, University of
Virginia, Charlottesville, VA
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