PHACTR1 and Hypertension: Multiple studies have shown that the rs9349379 locus is associated with changes in PHACTR1 expression which strongly implicates PHACTR1 as the causal gene at this locus.4,12 However, a previous study has also implicated endothelin-1 at this locus.11 Endothelin-1 is associated with both vasodilation and reduced blood pressure via its action on the ETB receptor on endothelial cells and vasoconstriction and hypertension via its action on ETA&B receptors on vascular smooth muscle cells.