Estrogen-related receptor alpha (ERR-alpha, ERR1, ESRL1; NR3B1) is a member of the orphan nuclear receptor family. ERR-alpha is expressed in the liver, kidney, brain, heart, uterus, vagina and cervix. ERR-alpha takes part in the cell cycle and the fatty acid metabolizing of the musculus skeleti. ERR-alpha was shown to interact with ER-alpha. ERR-beta (ERR2; NR3B2) is also expressed in the liver, brain, uterus, vagina, and cervix. ERR-beta has a role in early placental development. ERR-gamma (ESRRG; NR3B3) is expressed in the brain, kidney, testis, lung, adrenal gland, pancreas, placenta and bone marrow. ERR-gamma was shown to be located in the critical region for Usher's syndrome.