title: Retinoid X receptor and c-cerbA/thyroid hormone receptor regulate erythroid cell growth and differentiation.
abstract: Nuclear receptors are important regulators of erythroid cell development. Here we investigated the impact of retinoid X receptor (RXR), retinoic acid receptor (RAR), and of the c-erbA/thyroid hormone (T3) receptor (c-erbA/TR) on growth and differentiation of erythroid cells using an in vitro culture system of stem cell factor-dependent erythroid progenitors. RXR, RAR, and c-erbA/TR-specific ligands were found to induce erythroid-specific gene expression and to accelerate erythroid differentiation in culture, with T3 being most effective. Furthermore, while ligand-activated c-erbA/TR accelerated differentiation, unliganded c-erbA/TR effectively blocked differentiation and supported sustained progenitor growth in culture. Thus, c-erbA/TR appears to act as a binary switch affecting erythroid cell fate: unliganded c-erbA/TR supports growth while ligand-activated c-erbA/TR induces differentiation. Additionally, to determine the impact of RXR for erythroid cell development, dominant interfering mutant RXRs, lacking the transcriptional activator functions AF-1 and AF-2, or AF-2 only, or the entire DNA-binding domain, were introduced into erythroid progenitor cells via recombinant retrovirus vectors and analyzed for RXR-specific effects. It was found that expression of wild-type RXR and of the RXR mutants devoid of AF-1 and/or AF-2 supported a transient outgrowth of erythroid cells. In marked contrast, expression of the dominant interfering deltaDNA-binding domain RXR, containing a deletion of the entire DNA-binding domain, was incompatible with erythroid cell growth in vitro, suggesting a pivotal role of RXR for erythroid cell development.
authors.affiliation: Max-Delbrück-Center for Molecular Medicine, Berlin, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Bartůnĕk
authors.forename: M
authors.initials: M
authors.lastname: Zenke
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D002645:Chickens; D015672:Erythroid Precursor Cells / Q000166:cytology*; D005822:Genetic Vectors; D006801:Humans; D008024:Ligands; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000502:physiology*; D011988:Receptors, Thyroid Hormone / Q000502:physiology*; D047488:Retinoid X Receptors; D012190:Retroviridae; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D008024:Ligands; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D047488:Retinoid X Receptors; D014157:Transcription Factors