What are the genetic changes related to renal tubular dysgenesis ?
Mutations in the ACE, AGT, AGTR1, or REN gene can cause renal tubular dysgenesis. These genes are involved in the renin-angiotensin system, which regulates blood pressure and the balance of fluids and salts in the body and plays a role in kidney development before birth.  The renin-angiotensin system consists of several proteins that are involved in a series of steps to produce a protein called angiotensin II. In the first step, the renin protein (produced from the REN gene) converts a protein called angiotensinogen (produced from the AGT gene) to angiotensin I. In the next step, angiotensin-converting enzyme (produced from the ACE gene) converts angiotensin I to angiotensin II. Angiotensin II attaches (binds) to the angiotensin II receptor type 1 (AT1 receptor; produced from the AGTR1 gene), stimulating chemical signaling.  By binding to the AT1 receptor, angiotensin II causes blood vessels to narrow (constrict), which results in increased blood pressure. This protein also stimulates production of the hormone aldosterone, which triggers the absorption of salt and water by the kidneys. The increased amount of fluid in the body also increases blood pressure. Proper blood pressure, which delivers oxygen to the developing tissues during fetal growth, is required for normal development of the kidneys (particularly of the proximal tubules) and other tissues.  Mutations in the ACE, AGT, AGTR1, or REN gene impair the production or function of angiotensin II, leading to a nonfunctional renin-angiotensin system. Without this system, the kidneys cannot control blood pressure. Because of low blood pressure, the flow of blood is reduced (hypoperfusion), and the fetal tissues do not get enough oxygen during development. As a result, kidney development is impaired, leading to the features of renal tubular dysgenesis. Hypoperfusion also causes the skull abnormalities found in individuals with this condition.  Medications that block the activity of the angiotensin-converting enzyme or the AT1 receptor are used to treat high blood pressure. Because these drugs impair the renin-angiotensin system, they can cause an acquired (non-inherited) form of renal tubular dysgenesis in fetuses of pregnant women who take them. Acquired renal tubular dysgenesis can also result from other conditions that cause renal hypoperfusion during fetal development. These include heart problems, congenital hemochromatosis, and a complication that can occur in twin pregnancies called twin-to-twin transfusion syndrome.