**3.8 Developmental expression of PON2**

In mice, PON2 protein appears to be lowest directly after birth, steadily increasing with age up until Post-natal Day (PND) 21. A significant decrease in both protein and mRNA is noted from PND 21 to 30 and continuing to PND 60. In monkeys, PON2 protein levels were lower at mid-gestation and gradually increased up to infant age. This was followed by a decrease in the juvenile stage and a stabilization, in which similar levels were found in young adult and in aged monkey brains. The overall trend observed in both species reveals a possible window of susceptibility to oxidative stress in young adult mice and monkeys which may point to a change in cellular environment driving a decrease in PON2 expression [73].
