Angiotensinogen is a precursor of angiotensin II (Ang II),is expressed and synthesized largely in the liver and is cleaved by the enzyme renin in response to lowered blood pressure. It has a key role in mediating vascular constriction and regulating salt and fluid homeostasis. The resulting product,angiotensin I,is then cleaved by angiotensin converting enzyme (ACE) to generate the physiologically active enzyme angiotensin II. Mutations in this gene are associated with susceptibility to essential hypertension,and can cause renal tubular dysgenesis,a severe disorder of renal tubular development. Defects in this gene have also been associated with non-familial structural atrial fibrillation,and inflammatory bowel disease.