Hemoglobin biosynthesis in individual bursts from human adult peripheral and umbilical cord blood: analysis of the relative rates of synthesis of G gamma and A gamma globin chains

Establishment and characterization of a unique human cell line that proliferates dependently on GM-CSF, IL-3, or erythropoietin

We have established a novel cell line, designated as TF-1, from a patient with erythroleukemia, which showed complete growth dependency on granulocyte-macrophage colony-stimulating factor (GM-CSF) or on interleukin-3 (IL-3) and carried a homogeneous chromosomal abnormality (54X). Erythropoietin (EPO) also sustained the short-term growth of TF-1, but did not induce erythroid differentiation. These three hematopoietic growth factors acted on TF-1 synergistically. Transforming growth factor-beta and interferons inhibited the factor-dependent growth of TF-1 cells in a dose-dependent fashion, and monocyte-colony stimulating factor and interkeukin-1 enhanced the GM-CSF-dependent growth of TF-1. Ultrastructural studies revealed some very immature features in this cell line. Although TF-1 cells do not express glycophorin A or carbonyl anhydrase I, the morphological and cytochemical features, and the constitutive expression of globin genes, indicate the commitment of TF-1 to erythroid lineage. When induced to differentiate, TF-1 entered two different pathways. Specifically, hemin and delta-aminolevulinic acid induced hemoglobin synthesis, whereas TPA induced dramatic differentiation of TF-1 into macrophage-like cells. In summary, TF-1 is a cell line of immature erythroid origin that requires GM-CSF, IL-3, or EPO for its growth and that has the ability to undergo differentiation into either more mature erythroid cells or into macrophage-like cells. TF-1 is a useful tool for analyzing the human receptors for IL-3, GM-CSF, and EPO or the signal transduction of these hemopoietic growth factors.

Investigations of the simian ontogenic switch from fetal to adult hemoglobin at the progenitor cell level

The ontogenic switch from fetal to adult hemoglobin could result from discontinuous events, such as replacement of fetal erythroid progenitor cells by adult ones, or gradual modulation of the hemoglobin program of a single progenitor cell pool. The former would result in progenitors at midswitch with skewed fractional beta-globin synthesis programs, the latter in a Gaussian distribution. For these studies, we obtained bone marrow from rhesus monkey fetuses at 141-153 d (midswitch). Mononuclear cells were cultured in methyl cellulose with erythropoietin, and single BFU-E-derived colonies were removed and incubated with [3H]leucine. Globin synthesis was examined by gel electrophoresis and fluorography. The beta-globin synthesis pattern of single fetal colonies was skewed, and did not fit a normal distribution. The fetal pattern resembled the pattern of an artificial mixture of fetal and adult progenitors, suggesting that the fetal progenitor pool could contain populations with different beta-globin programs. This non-Gaussian distribution in the progenitors of midswitch fetuses is consistent with a discontinuous model for hemoglobin switching during ontogeny.

Characterization of the erythropoietic precursors (BFU-E) in a patient with juvenile chronic myelogenous leukaemia by the analysis of G gamma and A gamma globin chains

In order to investigate the pathogenesis of juvenile chronic myelogenous leukaemia (J-CML) we examined the biosynthetic rates of G gamma and A gamma globin chains in the erythropoietic bursts from the bone marrow of a patient with J-CML. Globin chains were labelled with 14C-labelled amino acids, separated by isoelectric focusing and quantitated by fluorography. The synthesis of gamma-chains in the erythropoietic bursts comprised 89.0% of the total non-alpha-chains. The G gamma:A gamma ratio was 0.67, which is within the ratios obtained in newborns. Furthermore, individual erythropoietic bursts contained varying ratios of both gamma and beta chains and all revealed more G gamma than A gamma chain synthesis. The relative proportions of G gamma and total gamma chain biosynthesis in 62 separate erythropoietic bursts were 0.69 +/- 0.06 and 0.86 +/- 0.06, respectively. Cumulative frequency distributions of individual bursts differing in the ratios of gamma/(gamma + beta) and G gamma/(G gamma + A gamma) approached normal frequency distributions. These results suggest that the levels of Hb F in J-CML are controlled by qualitative changes in a single population of erythropoietic precursors, in which normal switching of the G gamma:A gamma ratio has not occurred, rather than by the abnormal proliferation of an F-cell clone.

Switch from fetal to adult hemoglobin is associated with a change in progenitor cell population

To examine the switch from fetal to adult hemoglobin at the cellular level, erythroid progenitor cells from newborn infants and adults were cultured in methyl cellulose with erythropoietin. Individual erythroid colonies were labeled with [3H]leucine at various times, and globin synthesis patterns examined by gel electrophoresis and fluorography. The percent gamma- or beta-globin synthesis was determined from the total of gamma + beta, and the percent G gamma from the total of G gamma + A gamma. The nonparametric correlation coefficients of percent G gamma with percent gamma or beta were obtained. Each group of colonies at each time point was examined separately. In colonies from adult blood, the proportion of G gamma-synthesis did not correlate with the proportion of gamma-synthesis. Colonies from newborn blood fell into two groups. Those that developed from relatively mature progenitor cells, and were seen on day 14, showed a strong negative correlation of G gamma with beta-globin synthesis. However, those newborn colonies that developed from immature progenitors, and were seen later in culture (days 17 and 21), showed no correlation of G gamma with beta-synthesis. These findings are compatible with a clonal model for hemoglobin switching. Fetal progenitors, in which G gamma- and beta-syntheses are negatively correlated, are gradually replaced during ontogeny by adult progenitors. The adult progenitors produce more beta (less gamma), and the proportions of G gamma- and gamma- or beta-synthesis are not correlated.

The developmental change in the G gamma and A gamma globin. Proportions in hemoglobin F

The proportions of G gamma and A gamma globins in hemoglobin F were determined in fetuses around the 20th week of gestation, newborns, and children 3 weeks to 5 months of age. In the last group, the G gamma/G gamma + A gamma ratio decreased continously; there was a good correlation between the decline of G gamma with respect to total gamma and the decline of Hb F (r = 0.88). In contrast, there was virtually no difference in the gamma globin composition of Hb F between the fetuses and the newborns, i.e. in late pregnancy, the decrease in the synthesis of both gamma globins appears to be proportionate. The G gamma and A gamma globin genes may be inactivated in a sigmoidal fashion with time, thus producing a G gamma/G gamma + A gamma ratio which at first changes only slightly and then declines linearily.