PITX2 and preeclampsia: HDAC9 has emerged as an underlying contributor via its control of regulator of G-protein signaling (RGS) proteins that dampen GPCR activation [34,254], and GPCR kinases may also affect the localization of HDAC9 [88,100], creating an amplified feedback loop that reinforces excessive GPCR signaling in preeclampsia (Figure 4).