title: Hemoglobin F synthesis in vitro: evidence for control at the level of primitive erythroid stem cells.
abstract: The in vitro regulation of fetal hemoglobin (HbF was investigated in clones of cultured adult human erythroid cells by in situ immunofluorescent identification of the hemoglobins synthesized. Formation of Hb F-containing clones was enhanced by erythropoietin and by culture conditions favoring the proliferation of less-differentiated stem cells of the burst-forming-unit type. Burst-forming units differed in their capacity to direct Hb F synthesis in their terminally differentiated progeny. A class of early precursors that can produce descendent stem cells with or without commitment to Hb F production was identified. The findings suggest that the capability for expression of Hb F in terminally differentiated cells of the adult is determined at the level of less-differentiated erythroid stem cells with characteristics of burst-forming units. It is proposed that the regulation of Hb F synthesis in vivo is also linked to the process of differentiation of the erythroid stem cells and that the patterns of Hb F synthesis during ontogeny reflect the attainment of progressively higher levels of differentiation of erythroid stem cells as development proceeds.
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004920:Erythropoiesis; D004921:Erythropoietin / Q000494:pharmacology; D005319:Fetal Hemoglobin / Q000096:biosynthesis*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans
chemical_list: D004921:Erythropoietin; D005319:Fetal Hemoglobin
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