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PubMed1995

In vitro and in vivo myelotoxicity of CAI to human and murine hematopoietic progenitor cells.

Carboxyamido-triazole (CAI), an agent that targets calcium-sensitive signal transduction pathways, has both antiproliferative and antimetastatic properties. The objective of this study was to evaluate the myelotoxicity of CAI to normal human and murine hematopoietic cells. In vitro toxicity of CAI was determined by inhibition of myeloid [colony-forming unit-granulocyte/macrophage (CFU-gm)] and erythroid [burst-forming unit-erythroid (BFU-e)] colony formation in clonal assays. The effects of oral CAI on CD2F1 mouse marrow and splenic cellularity, marrow progenitor content, and peripheral blood cell counts were assessed in relation to plasma CAI levels. In vitro, CAI caused a concentration-dependent inhibition of CFU-gm and BFU-e colonies following continuous drug exposure. Murine CFU-gm and BFU-e were inhibited > 90% by 10 and 15 micrograms/mL CAI, respectively. However, suppression of human CFU-gm and BFU-e did not exceed 65% at the same concentrations. In vivo, CAI reduced the number of CFU-gm and BFU-e per femur after the initial dose and through day 4. Variations in colony inhibition paralleled changes in CAI plasma concentrations. While colony inhibition increased in vitro with escalating drug concentrations, this was not observed in vivo with additional CAI doses. The low toxicity of CAI in vivo combined with the significant difference between toxicity for human and mouse progenitors in vitro suggests a relatively low adverse potential to the bone marrow for this new signal transduction inhibitory agent.

Animals↗
PubMed1994

Bone formation by marrow osteogenic cells (MBA-15) is not accompanied by osteoclastogenesis and generation of hematopoietic supportive microenvironment.

This study was aimed at elucidating the relationship between osteogenic activity of marrow stromal cells and their ability to support hematopoiesis followed by the bone-remodeling process. We used the MBA-15 cell line, which expresses osteoblastic phenotype in vitro and forms bone in diffusion chamber. We have compared bone formation and hematopoietic responses elicited in vivo by these cells with the implantation of freshly isolated bone marrow cells (BMC) or demineralized tooth matrix (DTM). Both MBA-15 cells and BMC, implanted under the kidney capsule, yielded intramembraneous bone, but DTM, implanted subcutaneously, elicited endochondral bone. MBA-15 formed primary bone, mimicking only the initial sequential stages of the ossification process. Neither histologic signs of bone resorption and remodeling nor tartrate-resistant acid phosphatase (TRAP)-positive cells and marrow formation were observed. Bone formation was monitored biochemically. Functions for hematopoietic stem and committed cell content were measured by GM-CFU and BFU-E assays that confirmed the morphologic observations. In both BMC and DTM implantation, bone formation was followed by hematopoietic activity, osteoclastogenesis, and remodeling. We conclude that MBA-15 osteoprogenitor cells, despite their extensive bone formation ability, are unable to form a microenvironment supportive for hematopoiesis and osteoclastogenesis or to initiate bone remodeling.

Animals↗
PubMed2007

The transcription factor KLF11 can induce gamma-globin gene expression in the setting of in vivo adult erythropoiesis.

Previous studies in a fetal erythroid cell line demonstrated that the transcription factor, Krüppel-like factor 11 (KLF11), could specifically induce transcription from a gamma-globin gene promoter, and that this induction was mediated through a specific canonical CACCC cis-DNA binding motif. We report here that ectopic expression of KLF11 can also induce fetal gamma-globin gene expression in the setting of adult erythropoiesis both in vitro and in vivo. Studies in an adult-stage murine erythroleukemia (MEL) cell line demonstrated that retrovirus vector-mediated transduction of KLF11 could increase both the amount of expression from a basally active, but not from a overtly silenced, recombinant gamma-globin transgene, as well as the frequency of cells expressing this transgene. A similar pattern of gamma-globin gene induction was also observed both in vitro and in vivo following KLF11 transduction of bone marrow from mice containing a basally active gamma-globin transgene. These studies provide the first evidence that ectopic expression of a transcription factor can induce gamma-globin gene expression in vivo during adult erythropoiesis.

Animals↗
PubMed1991

Effects of recombinant human stem cell factor (SCF) on the growth of human progenitor cells in vitro.

We have studied the effect of recombinant human Stem Cell Factor (SCF) on the growth of human peripheral blood, bone marrow, and cord blood progenitor cells in semisolid medium. While SCF alone had little colony-stimulating activity under fetal bovine serum (FBS)-deprived culture conditions, SCF synergized with erythropoietin (Epo), granulocyte/macrophage colony-stimulating factor (GM-CSF), and interleukin 3 (IL-3) to stimulate colony growth. Colony morphology was determined by the late-acting growth factor added along with SCF. Of all the combinations of growth factors, SCF plus IL-3 and Epo resulted in the largest number of mixed-cell colonies--a larger number than observed with IL-3 and Epo alone even in FBS-supplemented cultures. These results suggest that SCF is a growth factor that more specifically targets early progenitor cells (mixed-cell colony-forming cells) and has the capacity to synergize with a wide variety of other hematopoietic growth factors to cause the proliferation and differentiation of committed progenitor cells. Our studies indicate that SCF may be the earliest acting growth factor described to date.

Bone Marrow Cells↗
PubMed1991

Transitional change of colony stimulating factor requirements for erythroid progenitors.

The course of the differentiation and proliferation of the human erythroid burst-forming units (BFU-E) to colony-forming units (CFU-E) was directly investigated using a combination of highly purified BFU-E, a liquid culture system, and the following clonal assay. Highly purified human blood BFU-E with a purity of 45-79% were cultured in liquid medium with recombinant human erythropoietin (rEP) and recombinant human interleukin-3 (rIL-3) to generate more differentiated erythroid progenitors. The cultured cells were collected daily for investigating the morphology, the increment in the number of cells and the clonality. Ninety percent of purified BFU-E required not only rEP but also rIL-3 for clonal development. By 7 days of liquid culture, the total cell number increased 237 +/- 20-fold above the starting cells, while erythroid progenitors increased 156 +/- 74-fold. As the incubation time in liquid culture increased, the cells continuously differentiated in morphology. Replating experiments with rEP combined with or without rIL-3 showed the following: 1) The number of erythroblasts that were part of erythroid colonies decreased with accompanying erythroid progenitor differentiation and proliferation. 2) As the incubation time in liquid culture increased, erythroid progenitors had a graded loss of their dependency on rIL-3 and a complete loss of dependency was observed after 3 days of liquid culture. At that time 85% of the erythroid progenitors gave rise to colonies of more than 100 erythroblasts which were equivalent to mature BFU-E. These studies provide a quantitative assessment of the loss of IL-3 dependency by BFU-E and indicate that the size of the generated erythroid colonies and their IL-3 requirement correlate with the erythroid differentiated state.

Adult↗
PubMed1992

Inhibition of human erythroid colony-forming units by interleukin-1 is mediated by gamma interferon.

IL-1 inhibits erythropoiesis in vivo and in vitro. This inhibition was studied by comparing the effect of recombinant human IL-1 (rhIL-1) on highly purified CFU-erythroid (E) generated from peripheral blood burst-forming units-erythroid (BFU-E) (mean purity 44.4%) with its effect on unpurified marrow CFU-E (mean purity 0.36%). Colony formation by marrow CFU-E was significantly inhibited by rhIL-1, while colony formation by highly purified CFU-E was not inhibited. However, purified CFU-E colonies were inhibited by rhIL-1 in the presence of autologous T-lymphocytes, and also by cell-free conditioned medium prepared from T-lymphocytes stimulated by rhIL-1. This inhibitory effect was ablated by neutralizing antibodies to gamma interferon (IFN), but not by antibodies to human IL-1, tumor necrosis factor, or beta IFN. Colony formation by highly purified CFU-E was also inhibited by recombinant human gamma IFN (rh gamma IFN). IL-1 and gamma IFN play significant roles in the pathogenesis of the anemia of chronic disease. These studies indicate that rhIL-1 inhibits CFU-E colony formation by an indirect mechanism involving T-lymphocytes and requiring gamma IFN and that gamma IFN itself is most probably the direct mediator of this effect.

Animals↗
PubMed1998

Kinetics of hematopoiesis in Dexter-type long-term cultures established from human umbilical cord blood cells.

In the present study, we have established Dexter-type long-term cultures (D-LTC) from human umbilical cord blood (UCB) and followed the kinetics of different hematopoietic progenitor cells (HPCs)--including multipotent (colony forming unit [CFU]-Mixture), erythroid (CFU-erythroid, BFU-E), and myeloid (CFU-granulocyte, CFU-macrophage, CFU-granulocyte/marcophage) progenitors as well as of morphologically recognizable erythroid, myeloid and lymphoid cells--during a nine-week culture period. D-LTC were also established from adult bone marrow (BM) as controls. On day 0, both UCB and BM showed similar total numbers of HPCs (about 310/10(5) cells), however, UCB showed a higher proportion of primitive HPCs (i.e., CFU-Mixture, CFU-granulocyte/macrophage and BFU-E). A poor adherent cell layer, consisting almost exclusively of macrophages, was developed in UCB D-LTC and this correlated with a continuous decline in HPC numbers throughout the culture period. In contrast, adherent cell numbers in BM D-LTC, including fibroblasts and macrophages, were two- to fourfold higher than in UCB cultures, and the numbers of HPCs were also significantly higher, reaching plateau levels between weeks 6 and 9. In both types of cultures, erythroid and multipotent progenitors declined relatively fast, reaching undetectable levels after five weeks of culture. Myeloid progenitors, on the other hand, were sustained longer (always at higher levels in BM cultures) and were still detected by week 9. Among myeloid progenitors, a shift towards the predominance of macrophage HPCs was observed, both in UCB and BM D-LTC, and this correlated with an increase in the proportion of mature monocytes and macrophages. Taken together, our results indicate that myeloid progenitor cell growth is deficient in UCB D-LTC and suggest that this is due to the impaired development of an adherent cell layer, unable to provide the factors and conditions required for their growth. Interestingly, throughout the culture period the total numbers of multipotent and erythroid progenitors were similar both in UCB and BM cultures regardless of the number and types of adherent cells present; this suggests that the stroma developed in D-LTC is not sufficient for the proliferation of these progenitor cells.

Bone Marrow Cells↗
PubMed1990

Molecular mechanisms underlying erythropoiesis: cycling activity of adult BFU-e relates to their requirement for c-myb function and potential for HbF synthesis.

Highly purified erythroid burst-forming units (BFU-e) from human embryonic liver, adult marrow and blood were manipulated in vitro by cytokine addition in order to explore their requirements for c-myb function and potential for fetal hemoglobin (HbF) synthesis, particularly as related to their cycling activity. c-myb is expressed at a minimal level and functionally required to a limited extent in quiescent adult BFU-e. However, c-myb is actively transcribed and stringently required for differentiation of actively cycling progenitors (embryonic BFU-e, embryonic and adult erythroid colony-forming units). The cycling activity of highly purified adult BFU-e, gradually enhanced by interleukin 3 (IL-3) addition, is strictly and directly related to both their functional requirements for c-myb and the level of myb mRNA expression in the progenitor population. It may be concluded that the transcriptional activity and the functional role of c-myb in early erythropoiesis are dependent upon the cycling activity of the erythroid progenitors. The reactivation of HbF synthesis in normal adult bursts, observed in the standard fetal calf serum-rich (FCS+) clonogenic system, is suppressed in cultures with a drastically limited growth of accessory cells (i.e., in FCS- or FCS+ Mo- conditions). In these cultures, addition of granulocyte/macrophage colony-stimulating factor (GM-CSF) or IL-3 induces a dose-related rise of gamma-chain synthesis, at least in part via a direct action at the BFU-e level. Preliminary studies involving priming of adult BFU-e with IL-3 in liquid phase suggest that the HbF potential is relatively low in quiescent BFU-e, but distinctly higher in actively cycling ones. It is postulated that the in vivo reactivation of HbF synthesis in bone marrow regeneration may be mediated via increased IL-3 and GM-CSF activity, leading to enhanced cycling and differentiation of BFU-e.

Adult↗
PubMed1994

Efficient isolation of human CD34 positive hemopoietic progenitor cells by immune panninga.

In this study we have assessed the use of soybean agglutinin (SBA) and CD34 microcellector devices for the selection of CD34 positive hemopoietic progenitor cells. Burst forming unit-erythroid (BFU-E), colony forming unit-granulocyte/macrophage (CFU-GM) and the recently developed multipotential human colony forming unit-type A (CFU-A) clonogenic assays were used to measure progenitor numbers in the starting mononuclear cell (MNC), the SBA negative, the nonadherent CD34 negative and the adherent CD34 positive fractions during panning. CFU-A progenitors were present at a relatively high incidence in the MNC fraction (220 per 10(5) MNC) and were enriched 15-fold in the adherent CD34 positive fraction. This progenitor incidence and enrichment were similar to those of CFU-GM and BFU-E. The mean recovery for CD34 positive cells was 2.3 x 10(6) cells per marrow aspirate. Analyses by flow cytometry demonstrated that 1-5% of input MNC were CD34 positive, that the purity of the CD34 fraction was approximately 80% and that the calculated recovery for CD34 positive cells was 61%. Recoveries for CFU-GM, BFU-E and CFU-A were between 18 and 40%. CFU-A progenitors were found exclusively in the adherent CD34 positive fraction, whereas a significant proportion of both CFU-GM and BFU-E were present in the nonadherent CD34 negative fraction. We propose that the Applied Immune Sciences (AIS) flasks preferentially bind the cells which express CD34 most strongly and that this is reflected in the finding of primitive CFU-A only in the CD34 positive fraction, with lineage-restricted progenitors found in both CD34 positive and negative fractions. This hypothesis is strengthened by data on long-term bone marrow cultures in which the CD34 positive fraction is better able to maintain output of CFU-GM compared with the CD34 negative fraction. In conclusion, relatively pure populations of CD34 positive cells may be rapidly and efficiently isolated from bone marrow samples with good recovery. The isolated cells show enhanced colony forming capacity in standard clonogenic assays and in the multipotential CFU-A assay.

Antigens, CD↗
PubMed1995

Comparison of the coexpression of CD38, CD33 and HLA-DR antigens on CD34+ purified cells from human cord blood and bone marrow.

Human umbilical cord blood (UCB) cells are currently considered as a potential source of stem cells for transplantation. However, it remains unclear whether a single collection of UCB contains enough progenitors to allow a successful engraftment in adult patients. We were interested in the comparison of the frequency of primitive progenitors in UCB and in human bone marrow (BM). UCB and BM CD34+ cells were purified and compared for their coexpression of CD38, CD33 and HLA-DR. UCB and BM mononuclear fractions were enriched in CD34+ cells using the CEPRATE LC system (CellPro, Bothell, WA). Double-labeling analysis with a flow cytometer showed that 67.9 +/- 7.2% of UCB CD34+ cells are CD38-, while in BM only 10.9 +/- 4.9% of CD34+ are CD38- (p < 0.001). Moreover, our study indicated that a significantly higher percentage of UCB CD34+ is CD33- (97.1 +/- 1.2%) compared to BM (61.8 +/- 8.6%) (p = 0.013). The coexpression of CD34 with HLA-DR was not significantly different in UCB and in BM (respectively, 86.3 +/- 2.7% and 92.7 +/- 5.1%). On the other hand, in vitro assays showed that the number of multipotent (colony-forming units granulocyte-erythroid-macrophage-megakaryocyte [CFU-GEMM]), myeloid (colony-forming units granulocyte-macrophage [CFU-GM]) and erythroid (burst-forming units-erythroid [BFU-E]) progenitors is lower in the CD34+ population from UCB than from BM. In conclusion, in UCB, we have found a significantly higher percentage of CD34+ cells which lacked the expression of CD38 and CD33 antigens suggesting that UCB contains higher proportions of immature progenitor cells (CD34+CD38- and CD34+CD33-) than BM. It seems thus likely that fewer UCB CD34+ cells than BM CD34+ cells would be required for sustained engraftment following transplantation.

Antigens, CD↗
PubMed1998

Involvement of H-ras in erythroid differentiation of TF1 and human umbilical cord blood CD34 cells.

To investigate the role of the ras gene in erythroid differentiation, a human erythroleukemic cell line, TF1, was transduced with a selectable retroviral vector carrying a mammalian wild type H-ras gene or a cytoplasmic dominant negative RAS1 gene. Transduction of TF1 cells with the wild type H-ras gene resulted in changes of cell types and up-regulation of erythroid-specific gene expression similar to that seen in differentiating erythroid cells. The number of red blood cell containing colonies derived from TF1 cells transduced with wild type H-ras cDNA was significantly increased and the cells in the colonies were more hemoglobinized as estimated by a deeper red color compared to those colony cells from mock or dominant negative RAS1 gene transduced TF1 cells, suggesting increased erythroid differentiation of TF1 cells after transduction of wild type H-ras in vitro. The mRNA levels of beta- and gamma-, but not alpha-, globin genes were significantly higher in H-ras transduced TF1 cells than those in TF1 cells transduced with mock or dominant negative RAS1 gene. Moreover, a 4kb pre-mRNA of the Erythropoietin receptor (EpoR) was highly expressed only in H-ras transduced TF1 cells. Additionally, human umbilical cord blood (CB) CD34 cells which are highly enriched for hematopoietic stem/progenitor cells were transduced with the same retroviral vectors to evaluate in normal primary cells the activities of H-ras in erythroid differentiation. Increased numbers of erythroid cell containing colonies (BFU-E and CFU-GEMM) were observed in CD34 cells transduced with the H-ras cDNA, compared to that from mock transduced cells. These data suggest a possible role for ras in erythroid differentiation.

Antigens, CD34↗
PubMed1999

The role of c-myb during the maturation of murine CFU-E.

Proper expression of the c-myb proto-oncogene is essential for definitive, but not primitive erythropoiesis. To examine the role of c-myb during adult erythropoiesis, we incubated purified murine colony-forming units (CFU-E) with a c-myb-specific antisense oligodeoxynucleotide (AS-oligo) in order to diminish expression levels. By western blot analysis, c-myb expression was reduced during the first seven hours of AS-oligo treatment as compared to untreated cells. We then quantitated the amount of heme synthesized in CFU-E treated with c-myb AS-oligo, a random sequence oligo or no oligo. No significant differences were seen in the amount of heme synthesized during 42 hours of erythroid culture with either high levels (1 U/mL) or physiological levels (20 mU/mL) of Epo. In contrast, CFU-E treated with an AS-oligo directed toward mRNA encoding the first enzyme of the heme biosynthetic pathway in erythroid cells (d-aminolevulinate synthase) demonstrated a 65% reduction in the amount of heme synthesized. We conclude that the major role of c-myb during hematopoiesis must be in progenitor cells antecedent to the CFU-E stage and may possibly involve the establishment of the genetic program directing the formation of red blood cells.

Animals↗
PubMedDate not supplied

Induction of fetal hemoglobin by propionic and butyric acid derivatives: correlations between chemical structure and potency of Hb F induction.

Short-chain fatty acids (C2-C9) induce fetal hemoglobin synthesis in primary cell cultures, primates, and patients. We carried out experiments to test whether relationships exist between chemical structure and the Hb F-inducing potential of several short-chain fatty acid derivatives. BFUe cultures were performed in the presence of propionic and butyric congeners, covering the full spectrum of substitutions of these molecules, including polar and non-polar groups, esters, and double bonds. We found that the fetal hemoglobin inducibility is related to the chemical structure of the inducing compound. This structure-activity relation depends on the length of carbon chain, the nature of the substitutions, and the position of more potent substitutions on the carbon chain. It appears that substitutions enhancing the inducibility of these compounds are (with decreasing potency): methyl > phenyl > hydroxy >> amino groups. Placement of these substitutions at a position distal to the carboxyl group enhances gamma-globin inducibility. Presence of the carboxyl group is prerequisite for gamma-globin inducibility.

Butyrates↗
PubMedDate not supplied

Role of Ets-1 in erythroid differentiation.

Members of the Ets gene family are known to be expressed in the hematopoietic tissue and some of them play a pivotal role in normal hematopoietic cell development. Ets-1 gene expression was analyzed in Friend Leukemia Cells (FLC) induced to erythroid differentiation by DMSO. We show that the level of Ets-1 protein and its binding activity decreases in FLC along erythroid differentiation of primary human progenitors. The same behavior was observed during normal erythroid differentiation. Moreover, FLC constitutively expressing Ets-1 show a decrease in TfR gene expression, globin mRNA and hemoglobin synthesis. These data indicate that a decrease in Ets-1 binding activity is required for a normal erythroid maturation and that a deregulated expression of this transcription factor may interfere with terminal erythroid differentiation.

Cell Differentiation↗
PubMed1998

Interleukin 3 (IL-3), but not stem cell factor (SCF) increases self-renewal by human erythroid burst-forming units (BFU-E) in vitro.

Interleukin 3 (IL-3) and stem cell factor (SCF) are both important regulators of early haemopoietic cell development. Here, we have compared their effects or the kinetics of erythroid burst formation by BFU-E in normal adult bone marrow. We grew the BFU-E in the presence of erythropoietin (Epo) alone, Epo + IL-3 or Epo + SCF and scored the numbers of subcolonies in individual bursts after 14 days. The data were plotted as the cumulative distribution of the numbers of subcolonies per erythroid burst then linearised by logarithmic transformation. Analysis of the data revealed that IL-3 increases the numbers of subcolonies in BFU-E whilst SCF increases the size of the subcolonies themselves. Experiments involving combinations of Epo + IL-3 + SCF and the delayed addition of IL-3 or SCF indicated that the actions of IL-3 and SCF are largely independent of one another. We conclude that: (1) IL-3 acts at an earlier stage of erythroid differentiation than SCF, and (2) it may be possible to classify haemopoietic growth factors according to their effects on cell kinetics in vitro.

Cells, Cultured↗
PubMed2002

Production of IL-10, TNF-alpha, IFN-gamma, TGF-beta1 by different populations of erythroid cells derived from human embryonal liver.

It has previously been determined that erythroid cells of mice are capable of expressing such cytokines as interleukin (IL) 1 alpha and beta, IL-4, IL-6, interferon gamma (IFN-gamma), granulocyte-macrophage colony-stimulating factor (GM-CSF) and transforming growth factor beta (TGF-beta). It has been shown that glycophorin A(+) (GlA(+)) and antigen erythroblasts (AG-EB(+)) (both human erythroid cells of embryonic origin) are also capable of producing a series of cytokines such as IL-1 beta, IL-2, IL-4 and IL-6. The aim of this work was to study the capacity of erythroid cells from human embryonic liver to produce such cytokines as IFN-gamma, TGF-beta1, tumour necrosis factor alpha (TNF-alpha) and IL-10. The erythroid cells were isolated by means of antibodies specific to erythroblasts (GlA and AG-EB), as well as those from single erythroid colonies. The production level of some cytokines varies insignificantly under the action of erythropoietin (Epo) and quantitatively differs in GlA(+) and AG-EB(+) erythroid cells. Hence, the erythroid cells express IFN-gamma, TGF-beta1, TNF-alpha and IL-10. The erythroid cells could be involved through the production of these cytokines in the regulation of such processes as self-renewal, proliferation and differentiation of cells of other blood-forming sites.

Cells, Cultured↗
PubMed1999

Gene expression in proliferating human erythroid cells.

A complete understanding of human erythropoiesis will require a robust description of transcriptional activity in hematopoietic cells that proliferate and differentiate in response to erythropoietin (EPO). For this purpose, we cultured peripheral blood mononuclear cells in the presence or in the absence of EPO and examined the transcriptional profile of those cells arising only in response to EPO. A distinct population of CD71( +) cells that demonstrated an average of six additional doublings in suspension culture and erythroid colony formation in methylcellulose was isolated. Suppression subtractive hybridization of mRNA isolated from those cells permitted the identification of transcribed genes. A summary of 719 expressed sequence tags (ESTs) describing 505 independent transcripts is provided here with a full analysis of each EST available at http://hembase.niddk.nih.gov. Several transcripts that matched genes previously reported in the context of erythroid differentiation including 4 cell surface proteins were expressed at this developmental stage. Active chromatin remodeling was suggested by the identification of 4 histone proteins, 4 high-mobility group proteins, 13 transcription factors, and 6 genes involved in DNA recombination and repair. Numerous genes associated with leukemic translocations were also recognized including topoisomerases I and II, nucleophosmin, Translin, EGR1, dek, pim-1, TFG, and MLL. In addition to known transcripts, 44 novel EST were discovered. This transcriptional profile provides the first genomic-scale description of gene activity in erythroid progenitor cells.

Antigens, CD↗
PubMed1999

Use of somatic cell fusion to reprogram globin genes.

The developmental phenomenon of hemoglobin switching occurs in all classes of vertebrates and is due to differential regulation of divergent globin genes which are arranged in chromosomally clustered families. By fusing erythroid cells of different developmental programs, it has been shown that erythroid nuclei of either early or late developmental stage can be reprogrammed, i.e. the gene switch can be reversed in adult erythroid nuclei and/or prematurely-induced in fetal/embryonic erythroid nuclei. Experiments with heterokaryons demonstrate that the reprogramming is due to trans-acting factors that are developmental-stage-specific. These results suggest the feasibility of using fusisome-carried sets of nuclear factors to reprogram somatic cells.

Animals↗