Erythroid gene expression is differentially regulated by erythropoietin, haemin and delta-aminolaevulinic acid in UT-7 cells

Abstract

Erythropoietin (Epo) is essential for the later stages of erythropoiesis, acting to promote cell survival and proliferation, but its role in differentiation remains to be defined. The UT-7 cell line exhibits both erythroid and megakaryocytic characteristics and can be induced to differentiate along the erythroid pathway by Epo or the megakaryocytic pathway by phorbol myristic acetate. We have compared the effects of Epo and the chemical inducers, δ-aminolaevulinic acid (δ-ALA) and haemin on the differentiation capacity of UT-7 cells. Epo alone promoted relatively early events in erythroid maturation, without significant changes in haemoglobin production or morphology. GATA-2 and c-myb were down-regulated by po, and GATA-2 was further down-modulated by the inducers. Conversely, SCL expression was up-regulated by Epo and further increased by haemin and δ-ALA. Epo caused an increase in the proportion of cells expressing cell surface glycophorin A (GPA) and up-regulated β- and γ-globin by several fold. Both haemin and δ-ALA caused a de novo increase in α-globin expression as well as enhancing Epo-induced β-globin expression; leading to a marked increase in haemoglobin production. These results suggest that haemoglobin production in UT-7 cells is limited by a deficiency of erythroid-specific aminolaevulinic acid synthase (ALAS-E) activity or globin synthesis as a consequence of their immaturity as a multipotential cell line.