Erythroid-extrinsic regulation of normal erythropoiesis by retinoic acid receptors.

Vitamin A and its derivatives (retinoids) are important regulators of haematopoiesis, acting via retinoic acid receptors (RARs). Epidemiological studies indicated an association of vitamin A deficiency with anaemia in humans. To define the requirements of RARs in erythropoiesis, we evaluated erythroid parameters in RAR germ-line deficient and conditional knock out mice with erythroid specific deletion of RARs. Adult RARγ(-/-) mice were anaemic, however, Epor-Cre Rara(fl/fl) , Epor-Cre Rarg(fl/fl) and Epor-Cre Rara(fl/fl) g(fl/fl) mice were normal, indicating a lack of an erythroid intrinsic RAR function. Therefore, erythroid-specific RAR function is dispensable for erythropoiesis and RARγ plays an erythroid extrinsic role in erythropoiesis.