cytochrome P450 family 2 subfamily R member 1
The CYP2R1 gene provides instructions for making an enzyme called 25-hydroxylase. This enzyme carries out the first of two reactions to convert vitamin D to its active form, 1,25-dihydroxyvitamin D3, also known as calcitriol. Vitamin D can be acquired from foods in the diet or can be made in the body with the help of sunlight exposure. When active, this vitamin is involved in maintaining the proper balance of several minerals in the body, including calcium and phosphate, which are essential for the normal formation of bones and teeth. One of vitamin D's major roles is to control the absorption of calcium and phosphate from the intestines into the bloodstream. Vitamin D is also involved in several processes unrelated to bone and tooth formation.
At least four mutations in the CYP2R1 gene have been found to cause vitamin D-dependent rickets type 1B (VDDR1B). This disorder of bone development is characterized by low levels of calcium (hypocalcemia) and phosphate (hypophosphatemia) in the blood, which lead to soft, weak bones that are prone to fracture. A common feature of this condition is abnormally curved (bowed) legs.
The CYP2R1 gene mutations that cause this condition severely reduce or eliminate the function of 25-hydroxylase. As a result, vitamin D does not get converted to its active form and cannot control mineral absorption. The resulting reduction in calcium and phosphate absorption from the intestines means there is less of these minerals to be deposited in developing bones (bone mineralization), which leads to soft, weak bones and other features of VDDR1B. Hypocalcemia also causes muscle weakness in some affected individuals.
- cytochrome P450 2R1
- cytochrome P450, family 2, R1
- cytochrome P450, family 2, subfamily R, polypeptide 1
- vitamin D 25-hydroxylase