Suppression of Erythroid-Specific 5-Aminolevulinate Synthase Using Short-Interfering RNA Alters Iron Metabolism and Inhibits Terminal Differentiation of Human Erythroleukemia Cells.

Erythroid-specific 5-aminolevulinate synthase (ALAS2) is the first and the rate limiting enzyme for heme biosynthesis in erythroid cells. ALAS2 plays a critical role in hemoglobin synthesis and erythrocyte maturation, since targeting the ALAS2 gene results in embryonic death in mice because of severe anemia. In humans, heritable mutations of the ALAS2 gene are responsible for X-linked sideroblastic anemia (XLSA). However, the effect of suppressed expression of ALAS2 on erythroid cell differentiation has not been examined in human cells. We therefore addressed this question, by stably suppressing ALAS2 mRNA with short-interfering RNA (siRNA) in a human erythroleukemia cell line, YN-1. After cloning of cells expressing low ALAS2 (ALAS2^low cells), cells were induced to undergo erythroid differentiation by treatment with transforming growth factor beta1 (TGF-β1). Gene expression profiles of induced and uninduced cells were examined, including genes involved in globin synthesis and iron metabolism. Hemoglobin production, as judged by o-dianisidine staining, was significantly lower in ALAS2^low cells than in control cells both before and after erythroid differentiation. Both alpha and gamma globin mRNA levels were also reduced in ALAS2^low cells, compared with control cells. Decreased heme synthesis as well as reduced globin production in ALAS2^low erythroid cells are consistent with our previous findings in murine erythroleukemia cells studied by antisense technology (