Odd protein may
spur Alzheimer’s
Unusual amyloid-beta sows
destruction in mouse brains
By Laura Sanders
Scientists have caught tiny amounts of
a strangely shaped protein — a relative
of a well-known suspect in Alzheimer’s disease — spreading destruction
throughout the brains of mice. If a similar process happens in the human brain,
it could help explain how Alzheimer’s
starts and even suggest ne w ways to stop
the disease’s spread.
Many researchers believe the abundance of a molecule called amyloid-beta
in the brain is a key factor in Alzheimer’s
disease. A-beta commonly takes the
form of a chain of 42 protein building
blocks called amino acids.
The new study chronicles the dangers
of a modified A-beta that lacks the first
two amino acids in the chain. Capping
this stub is a rare, circular amino acid
called pyroglutamate. Until recently,
this form “has been largely ignored as
some minor, mysterious form of amy-
loid-beta,” says study coauthor George
Bloom of the University of Virginia.
Yet even trace amounts of this version,
called pyroglutamylated A-beta, or
pE A-beta, are devastating to mouse
nerve cells, he and colleagues report
online May 2 in Nature.
“This opens up a whole new view
of the disease.” — RUDY TANZI
tangles up inside nerve cells. Mice genetically designed to lack tau were largely
immune to the ill effects of pE A-beta,
the team reports. Scientists don’t yet
understand exactly how tau and A-beta
interact.
It’s not clear whether the results in
mice will apply to people. Bloom and
his colleagues detected pE A-beta in
three out of three postmortem brains of
people diagnosed with Alzheimer’s, and
one out of three from people without the
disease.
The study may have uncovered one
of the first steps in a long disease process, says Tanzi. “This puts even more
emphasis on early detection of the disease before symptoms appear,” he says.
“We really need to hit this disease early.”
The research also points out one
potential new way to do that. Some of
the Nature paper’s authors are involved
with a Germany-based company called
Probiodrug that is developing a medicine designed to curb pE A-beta production in the brain. In 2011, the company
announced positive results from preliminary safety tests of the drug in healthy
volunteers. s
Snakes swirl when eyes jump
Tiny eye movements and blinking can make perfectly frozen snakes appear
to dance, a new study shows. The results help explain the mystery of how the
“rotating snakes” illusion tricks the brain.
Earlier studies have suggested that the perception of motion is triggered
when the eyes drift slowly away from a central target when viewing the illusion.
But by tracking eye movements in eight volunteers, vision neuroscientists at
the Barrow Neurological Institute in Phoenix found a different explanation.
Participants held down a button when the snakes seemed to swirl and lifted
the button when the snakes appeared still. Right before the snakes started
to move, participants began blinking more and making short jumpy eye
movements called microsaccades, Jorge Otero-Millan, Stephen Macknik and
Susana Martinez-Conde report in the April 25 Journal of Neuroscience. When
volunteers’ rates of microsaccades slowed down, the visual illusion faded and
the snakes were more likely to stop moving.
The results join a growing number of studies that use magic tricks and illusions to reveal people’s perceptual mistakes, such as seeing motion where
there is none. Studying the mismatch between perception and reality may lead
to a deeper understanding of the mind. — Laura Sanders
