PRG2 and Down syndrome: PRG2, which encodes the major basic protein of eosinophil, is one of the most highly expressed genes during human pregnancy, and low PRG2 levels can predict both Down syndrome and PE.[25] As both low oxygen and cAMP are known to play a central role in placental function, their regulation of STC-1 points to a potential role of this gene in the protection from prolonged placental hypoxia seen in PE.