Mammalian offspring may be more anxious when they reach adulthood if they are deprived of certain hormones while developing in the womb. The findings, reported in Nature Communications this week, reveal new insights into the role of the placenta in long term programming of emotional behaviour.
Insulin-like growth factor-2 has been shown to play a major role in foetal and placental development in mammals and changes in expression of this hormone in the placenta and foetus are implicated in growth restriction in the womb. Although intrauterine growth restriction is known to affect the development of neonates, the long term consequences are not fully understood. Lawrence Wilkinson and colleagues examine the adult behaviour of mice that lacked insulin-like growth factor-2 in the placenta only and find that these mice exhibit increases in behavioural traits related to anxiety, which are accompanied by specific changes in brain gene expression related to this type of behaviour. Although these studies were carried out in mice, these findings may have wider implications for human development. However, further studies will be needed to determine the extent to which this is true.