Genetics of uncontrolled brain growth in autism identified

Faulty genetic mechanisms particularly active in early life may lead to people developing autism, research suggests.

A study, led by Dr Eric Courchesne at the University of California, in the USA, investigated changes in the DNA and RNA in post-mortem brains of patients with autism. They found important differences in the expression of genes between children and adults with autism, and compared to controls.

Earlier work by Dr Courchesne suggested that in people with autism the prefrontal cortex - a region of the brain associated with social and communication skills - is larger than normal. The current study goes some way to suggesting why this may be.

The researchers found that many of the misfiring genes in the brains of the autistic children studied were involved in brain cell growth, leading to an excess of brain cells that Dr Courchesne had previously identified. The problem would appear to begin during the second and third trimester of pregnancy, when most brain cells are created.

Dr Courchesne explained: 'Essentially, the wiring pattern for the brain goes wrong and you don't get normal development'.

However, by examining the DNA and RNA profiles of brain tissue from adults with autism, the researchers also uncovered evidence that the brains of people with autism may re-wire in an attempt to counteract the effects of the disorder.

Dr Courchesne says that these changes 'are telling us that the brain development problem hasn't stopped. It is on-going. There may be signals or genetic changes that are attempting to deal with the original problem. That would seem to offer a potential target for pharmaceuticals to improve the remodelling'.

Nonetheless, other researchers dispute that there is an increase in the size of the brain in autistic patients. In particular, one study demonstrated an increase in the incidence of microcephaly, a condition in which people are born with small brains, in patients with autism.

However, the current study is the first to identify genetic changes which can explain a change in brain size and structure in people with autism. Dr Courchesne said: 'We are getting at core knowledge. If we confirm that the starting point is gene activity, we can do something about it, because gene activity can be modified'.