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, 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.