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Biomedicine

Testing Autism Drugs in Human Brain Cells

A method involving pluripotent stem cells could lead to personalized

treatment of the disease.

* Thursday, November 11, 2010

* By Chu

Autism is a highly complex disorder affecting one in every 110 children

born in the United States. The disease's genetic profile and behavioral

symptoms fluctuate widely from case to case, and this variability has frustrated

scientists' efforts to identify effective treatments. A new study suggests

that autism could eventually be a target for personalized treatment, targeted

to a patient's own neurons.

A team from the University of California, San Diego, and the Salk Institute

for Biological Studies devised a way to study brain cells from patients

with autism, and found a way reverse cellular abnormalities in neurons that

have been associated with autism.

The researchers took skin biopsies from patients with a severe form of

autism called Rett syndrome, and genetically reprogrammed those cells into

pluripotent stem cells. Pluripotent stem cells have the power to differentiate

into any kind of cell in the body, depending on environmental cues during

early development. The team differentiated the stem cells into fully functioning

neurons, and then studied their functioning. They found that neurons

derived from patients with Rett syndrome showed certain abnormalities, including

markedly smaller cell bodies, dendrite connections, and decreased

cell-to-cell communication.

By treating these patient-derived neurons with an experimental drug, the

researchers could reverse the cellular abnormalities. The findings, published

today in the journal _Cell_ (http://www.cell.com/) , could give scientists a

powerful tool for pinpointing the causes of autism and other brain

disorders, and a way to choose targeted treatments.

" It took us two years to finish this project, and personalized medicine

might not be that far off, " says Carol Marchetto, first author of the paper and

a postdoctoral researcher at the Salk Institute. " In the lifetime of a

patient, you could go from his skin sample to a reprogrammed cell, to

differentiating into a neuron, and find drugs that could be used on that

patient. "

Rett syndrome, which mostly affects girls, can cause highly impaired social

and communication skills, which become apparent soon after a child learns

to walk and talk. Patients with Rett can experience increased difficulty

breathing and controlling their movements, and can develop repetitive and

compulsive behaviors similar to other forms of autism.

Marchetto sees Rett syndrome as a gateway to the broader study of autism,

since many other forms of autism share behavioral and genetic similarities

with Rett syndrome.

Most cases of autism seem to stem from a combination of genetic

abnormalities, but Rett arises from a single gene mutation, found on the MeCP2

gene on

the X chromosome. In girls, one of two X chromosomes carries the mutation,

and during fetal brain development, one chromosome is activated within each

brain cell, seemingly at random. Rett patients can exhibit varying

percentages of brain cells carrying the mutation, which can manifest as varying

levels

of severity of the disorder.