This week the New Scientist magazine published an article about how the variation of a particular gene may account for as many as 15% of autism cases. Scientist Hakon Hakonarson of the Children’s Hospital of Philadelphia led a team that screened DNA from more than 2500 autism sufferers and 7000 healthy volunteers and identified a genetic mutation that was very common in autism sufferers.
It is believed that the mutation supports the idea that autism is in some cases caused by a breakdown in connections between brain cells. Previously studies have implicated several genes in causing autism but according to Hakonarson “they are extremely rare and account for a very small proportion of autism.”
It was found that many of the healthy volunteers also possessed the mutation, so it is thought that it contributes to autism rather than causing it outright. The gene in question sits on chromosome 5, between genes CAD10 and CAD9. These particular genes encode proteins that enable neurons to connect and communicate with each other. CAD10 is expressed in the precise regions of the brain that appear abnormal in people with autism. Hakonarson believes that the recently discovered gene regulates CAD9 and/or CAD10 and its mutation may disrupt this regulation.
Hakonarson also says that because other, rarer genes have been linked to autism and cell adhesion, both of which are necessary for neuron connection, it is possible that a breakdown in neural connections during brain development might underlie some autism cases. The evidence from this current study says that many more cases might have this gene mutation as their cause.
It is hoped that understanding the genetics of autism might eventually lead to genetic screening for babies. This would hopefully lead to early behavioural intervention being used to encourage more normal brain development in those with a higher risk of autism.
Geddes, L 2009, ‘Gene discovery may be common cause of autism’, New Scientist, vol. 202, no.2706, p11.
