Pacing mutation 'causes brain defect'
Mutations in a gene can cause severe mental impairment by changing the pace the brain develops, a team of US researchers say.
They said mutation to the SYNGAP1 gene "rains down chaos" on the way connections between brain cells form.
Experiments in mice, published in the journal Cell, showed that correcting the error later in life led to no improvement.
The scientists said a cure was possible, but only at a young age.
SYNGAP1 mutations are known to cause severe intellectual disability so researchers at the Scripps Research Institute, in Florida, analysed mice with similar mutations.
Prof Gavin Rumbaugh said: "SYNGAP1 is one of the most important genes in cognition.
"So far, every time a mutation that disrupts the function of SYNGAP1 has been found, that individual's brain simply could not develop correctly."
It regulates the formation of synapses - the point where two brain cells meet and "talk" to each other.
At two weeks old, the mice with the mutation had much higher levels of communication between brain cells than was normal.
"You might think this accelerated development of brain circuits would make you smarter," said Prof Rumbaugh.
"We think that early maturation of these excitatory synapses disrupts the timing of later developmental milestones.
"It rains down chaos on this complex process, preventing normal intellectual and behavioural development."
The result was mice with learning difficulties which also developed seizures.
The research team corrected the mutation in adult mice, however, it was too late to change the way the brain functioned.
They believe that intervening early is "essential" and this could have implications for any attempts to treat people. Prof Rumbaugh said he thought a cure was possible.