New Study Sheds Light on Genetic Mutation Linked to Autism

gene mutationA study utilizing mouse models has found new evidence towards how autism develops. The transgenic mouse model could lead to improvements in the diagnostic and treatment process for those on the autism spectrum.

Researchers at Vanderbilt University recently inserted a genetic variation into mice, creating a mutation which is commonly found in people with autism, ADHD, and bipolar disorder. This mutation affects the function of the dopamine transporter (DAT), a protein that regulates the brain’s supply of the neurotransmitter by removing excess dopamine from the synapse (the space between nerve cells).

The DAT mutation in individuals with autism causes the transporter to leak dopamine. Dr. Randy Blakely, senior author of the report, states, “[It’s like] a vacuum cleaner in reverse.” The mice with leaky DAT proteins have too much dopamine in and around their synapses, resulting in unusual behaviors. For example, they exhibited rapid, sudden movements, which they described as a “darting behavior”. While other mice were quiet and mostly unresponsive when researchers picked them up, those with the mutation were hyperactive, and as Dr. Blakely states, they would “take off”.

Dr. Blakely adds, “Early on, we could tell which ones carried the mutation by observing this response.” In addition, typical mice often explore their cages, while the mice with the mutation did not. Dr. Blakely states, “We wonder whether this may be a sign that the behavior is driven less by searching for clues to appropriate behavior versus acting on innate impulses.”

The effects of both amphetamine and methylphenidate (Ritalin) were also affected by the mutation. In neurotypical individuals and animals, the stimulants flood the synapse with dopamine, creating hyperactivity. However, when given to the mice with the mutation, the drugs quelled hyperactive and impulsive behaviors. As a result, Dr. Blakely and his team are contemplating how Ritalin may reduce the dopamine leak in children with autism and ADHD. He states, “These mice may give us much better clues as to how these drugs are acting.”

The darting mice have exposed specific behaviors that are directly linked to a specific mutation, as well as how Ritalin may suppress the behaviors to an extent. Dr. Blakely and his team are now focused on how to find the optimal treatments for other specific mutations.

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