2011-11-29 11:15:00
Cells taken from people with a rare syndrome linked to autism could help
explain the origins of the condition, scientists suggest.
The Stanford University team turned skin cells from people with "Timothy
syndrome" into fully-fledged brain cells.
The abnormal activity found in these cells could be partially corrected using
an experimental drug, Nature Medicine reports.
UK researchers warned the findings might not apply to everyone with autism.
Compared with the hundreds of thousands of people worldwide thought to show
characteristics of autism, "Timothy syndrome" is vanishingly rare, affecting an
estimated 20 people across the planet.
People who have the syndrome frequently display autistic behaviour, such as
problems with social development and communication.
Because it is caused by a single gene defect rather than a combination of small
genetic flaws, each making a tiny contribution, it presents a useful target for
scientists looking to examine what goes wrong in the developing brain of a
child with autism.
Ready for work
The US researchers used a technique developed recently to generate brain cells
called neurons from only a sample of the patient's skin.
This allowed them to examine their development in the laboratory, and even use
them to test out possible treatments.
They found obvious differences between neurons grown from Timothy syndrome
patients, and those from healthy "control" subjects.
The healthy neurons developed into different subtypes, ready for work in
different regions of the brain.
In contrast, the proportion of neurons developing into each subtype was
different in the Timothy syndrome samples - more were equipped to work in the
upper part of the cerebral cortex, and fewer in the lower part.
This meant there were fewer neurons equipped to work in a part of the brain
called the corpus callosum, which has the role of helping the left and right
"hemispheres" of the brain communicate.
These differences echoed those already observed in mice specially bred with the
Timothy syndrome genetic fault.
In addition, the neurons were making too much of a particular body chemical
linked to the manufacture of dopamine and norepinephrine, which play a
significant role in sensory processing and social behaviour.
Dr Ricardo Dolmetsch, who led the study, said that the abnormalities found
tallied with other evidence that autism was due in part to poor communication
between different parts of the brain.
The team managed to reduce significantly the number of these malfunctioning
neurons by adding a drug as they developed.
This, they said, meant it might be possible one day to treat this defect in a
real patient, although the drug used was not currently suitable for children
due to side-effects.
The National Autistic Society gave a cautious welcome to findings, but warned
that they did not necessarily offer insights into every form of autism.
Researcher Georgina Gomez said: "Timothy syndrome is only one form of autism
and so these findings only give a very limited picture of what might cause the
condition.
"More work would need to be done to substantiate this particular piece of
research."