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EXTREME differences in the way genes are expressed by fetuses with Down’s syndrome could point to ways to treat the condition in the womb.

The disorder arises when some or all of an extra copy of chromosome 21 is present, but exactly how this additional set of genes disrupts development, leading to learning difficulties and other symptoms of Down’s, isn’t clear.

Now and colleagues at Tufts Medical Center in Boston have found 414 genes – many not on chromosome 21 – that are expressed differently in the amniotic fluid surrounding fetuses with the disorder (Proceedings of the National Academy of Sciences, ).

Most of the genes are involved in cells’ ability to deal with oxidative stress, in which reactive oxygen products of metabolism harm cells. Oxidative stress has been associated with Down’s syndrome before. Bianchi suggests that via these genes it could play a role in some of the symptoms of Down’s, including abnormal brain growth. She concludes that finding drugs to alter the expression of these genes could mitigate the effects of oxidative stress, treating some symptoms of Down’s prenatally.

, a physiologist at Johns Hopkins University in Baltimore, Maryland, says that mitigating the effects of oxidative stress in the womb could be helpful, but cautions that it is likely to be just one of the contributing factors to the symptoms of Down’s syndrome.