THE genetics of autism may be simpler than we thought. It has long been known to have a genetic component, but how can several autistic children be born in one family, while another family has just one child with the condition? Complex interactions between many genes had been blamed, but now Michael Wigler of Cold Spring Harbor Laboratory in New York has a simpler explanation.
His team analysed three databases of high-risk families and noticed that sons had a 50 per cent risk of autism, suggesting that a dominant mutation 鈥� one that causes disease even when a healthy copy of the gene is present 鈥� was to blame. They combined this with observations that autism is rare in girls, who are thought to have some genetic resistance to it, and that autistic children often have new mutations in their DNA, thought to have arisen in a parent鈥檚 egg or sperm.
Wigler thinks that when such a one-off mutation is dominant it will trigger autism in just that child and only if it is a boy. A girl would usually become a carrier of the mutation, but her own sons would have a 50 per cent risk of inheriting it, possibly leading to several autistic children (Proceedings of the National Academy of Sciences, ).
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