Proportion of fetal hemoglobin synthesis decreases during erythroid cell maturation.

Abstract

Peripheral blood mononuclear cells from pregnant and postpartum women were cultured in vitro with erythropoietin. Burst-forming unit (BFU-E)derived erythroid colonies composed of immature erythroblasts with low hemoglobin contents were observed by day 8 of culture. By day 12 of culture, numerous BFU-E-derived erythroid colonies with high hemoglobin contents were present. The Y/(y + f) globin synthetic ratio was approximately 12% in the early cultures and 6% in the late cultures, indicating that the proportion of fetal hemoglobin synthesis decreases during erythroid cell maturation. These studies also reveal that the capacity for fetal hemoglobin production by peripheral blood BFU-E in vitro is not altered during pregnancy.The major hemoglobin in humans during intrauterine life is fetal hemoglobin, a2Y2. Adult hemoglobin, a232, is first detected at around the 10th week of gestation and accounts for approximately 10% of all hemoglobins present until about the 30th week of gestation, when increasing amounts of adult hemoglobin are produced (1). By the time the infant is 6 months old, most of the hemoglobin present is adult hemoglobin (2). The mechanisms for the switching of hemoglobins during fetal development are presently not clear (3). These orderly ontogenetic changes provide an excellent model for studying gene regulation and expression. In addition, elucidation of the mechanisms for hemoglobin switching can provide a potentially useful approach to the therapy of patients with genetic disorders involving the j globin chain.Immature erythroid stem cells, burst-forming units that respond to erythropoietin (BFU-E), are present in adult human peripheral blood and can proliferate and differentiate into large colonies of erythroblasts in vitro (4, 5). These erythroblasts, derived from normal adult individuals, synthesize a substantial amount of fetal hemoglobin (6-8). Because HbF is increased in maternal peripheral blood during pregnancy (9-11), the present investigation was undertaken to determine if peripheral blood BFU-E in pregnant women have an increased capacity for HbF production in culture and to study the pattern of HbF synthesis during erythroid cell maturation in vitro. Evidence is presented that the capacity for HbF production by peripheral blood BFU-E in vitro is not altered during pregnancy. These studies also reveal that the proportion of HbF synthesis decreases during erythroid cell maturation. A preliminary report of these studies has been published elsewhere (12). METHODSSubjects. Forty-four pregnant and postpartum (3-7 months) women were studied. All women were healthy and had no known diseases or complications. Appropriate consent was obtained. [50][51][52][53][54][55][56][57][58][59][60] Ci/mmol; 1 Ci = 3.7 X 1010 becquerels), obtained from New England Nuclear, was added to each plasma clot on either day 6 or day 7, and either day 11 or day 12 of culture. Twenty-four hours later, 10 plasma clots thus labeled were pooled and washed twice with phosphate-buffered saline. Three milligrams o...

Erythropoietin changes the globin program of an interleukin 3-dependent multipotential cell line.

“…Several previous studies have shown that Epo, apart from implementing the terminal maturation program, produces differences in the globin species formed (23)(24)(25)(26)(27)(28)(29). These changes, like those reported here for B6SUtA cells, could be effected by Epo in any one of several different direct or indirect ways.…”

Erythropoiesis is Distinct at Each Stage of Ontogeny

“…100 000 cells increased by the peak day, the relative frequency between groups remained similar. The number of colonies/ 100 000 cells previously reported for fetal (7)(8)(9), newborn (3,5,6,8,13,17,(20)(21)(22)(23), and adult (5,6,8,12,18,20,(24)(25)(26)(27) blood cultures were 40-500,9-220, and 2-256, respectively. Our values fall within the ranges reported by others.…”

Human embryonic zeta-globin chains in adult patients with alpha-thalassemias.

“…Hematological parameters were determined by standard laboratory procedures, using a Coulter S electronic counter. Hemoglobin studies, including starch gel electrophoresis, determinations of Hb A2 by microcolumn chromatography (normal range 1.8-3.3%) and Hb F by the Betke method (normal range 0.4-1.2%), were done as previously described (7). Hb H inclusion bodies in peripheral blood erythrocytes were carefully searched for under a light microscope, after the blood was incubated with brilliant cresyl blue (British Drug House) for 2 hr at 37°C (8).…”