Absence of blood formation in mice lacking the T-cell leukaemia oncoprotein tal-1/SCL

Chromosomal translocations associated with malignancies often result in deregulated expression of genes encoding transcription factors. In human T-cell leukaemias such regulators belong to diverse protein families and may normally be expressed widely (for example, Ttg-1/rbtn1, Ttg-2/rbtn2), exclusively outside the haematopoietic system (for example, Hox11), or specifically in haematopoietic cells and other selected sites (for example, tal-1/SCL, lyl-1). Aberrant expression within T cells is though to interfere with programmes of normal maturation. The most frequently activated gene in acute T-cell leukaemias, tal-1 (also called SCL), encodes a candidate regulator of haematopoietic development, a basic-helix-loop-helix protein, related to critical myogenic and neurogenic factors. Here we show by targeted gene disruption in mice that tal-1 is essential for embryonic blood formation in vivo. With respect to embryonic erythropoiesis, tal-1 deficiency resembles loss of the erythroid transcription factor GATA-1 or the LIM protein rbtn2. Profound reduction in myeloid cells cultured in vivo from tal-1 null yolk sacs suggests a broader defect manifest at the myelo-erythroid or multipotential progenitor cell level.

Mouse model of X-linked chronic granulomatous disease, an inherited defect in phagocyte superoxide production

Chronic granulomatous disease (CGD) is a recessive disorder characterized by a defective phagocyte respiratory burst oxidase, life-threatening pyogenic infections and inflammatory granulomas. Gene targeting was used to generate mice with a null allele of the gene involved in X-linked CGD, which encodes the 91 kD subunit of the oxidase cytochrome b. Affected hemizygous male mice lacked phagocyte superoxide production, manifested an increased susceptibility to infection with Staphylococcus aureus and Aspergillus fumigatus and had an altered inflammatory response in thioglycollate peritonitis. This animal model should aid in developing new treatments for CGD and in evaluating the role of phagocyte-derived oxidants in inflammation.

Rescue of GATA-1-deficient embryonic stem cells by heterologous GATA-binding proteins

Totipotent murine embryonic stem (ES) cells can be differentiated in vitro to form embryoid bodies (EBs) containing hematopoietic cells of multiple lineages, including erythroid cells. In vitro erythroid development parallels that which is observed in vivo. ES cells in which the gene for the erythroid transcription factor GATA-1 has been disrupted fail to produce mature erythroid cells either in vivo or in vitro. With the EB in vitro differentiation assay, constructs expressing heterologous GATA-binding proteins were tested for their abilities to correct the developmental defect of GATA-1-deficient ES cells. The results presented here show that the highly divergent chicken GATA-1 can rescue GATA-1 deficiency to an extent similar to that of murine GATA-1 (mGATA-1), as determined by size and morphology of EBs, presence of red cells, and globin gene expression. Furthermore, GATA-3 and GATA-4, which are normally expressed in different tissues, and a protein consisting of the zinc fingers of GATA-1 fused to the herpes simplex virus VP16 transcription activation domain were able to compensate for the GATA-1 defect. Chimeric molecules in which both zinc fingers of mGATA-1 were replaced with the zinc fingers of human GATA-3 or with the single finger of the fungal GATA factor areA, as well as a construct bearing the zinc finger region alone, displayed rescue activity. These results suggest that neither the transcription activation domains of mGATA-1 nor its zinc fingers impart erythroid cell specificity for its action in vivo. Rather, it appears that specificity is mediated through the cis-acting control regions which determine spatial and temporal expression of the GATA-1 gene. Furthermore, our results demonstrate that the zinc finger region may have a biological function in addition to mediating DNA binding.

The C-terminal zinc finger of GATA-1 or GATA-2 is sufficient to induce megakaryocytic differentiation of an early myeloid cell line

The GATA-1 and GATA-2 transcription factors, which each contain two homologous zinc fingers, are important hematopoietic regulators expressed within the erythroid, mast cell, and megakaryocytic lineages. Enforced expression of either factor in the primitive myeloid line 416B induces megakaryocytic differentiation. The features of their structure required for this activity have been explored. The ability of 12 GATA-1 mutants to promote 416B maturation was compared with their DNA-binding activity and transactivation potential. Differentiation did not require any of the seven serine residues that are phosphorylated in vivo, an N-terminal region bearing the major transactivation domain, or a C-terminal segment beyond the fingers. Removal of a consensus nuclear localization signal following the second finger did not block differentiation or nuclear translocation. The N-terminal finger was also dispensable, although its removal attenuated differentiation. In contrast, the C-terminal finger was essential, underscoring its distinct function. Remarkably, only 69 residues spanning the C-terminal finger were required to induce limited megakaryocytic differentiation. Analysis of three GATA-2 mutants led to the same conclusion. Endogenous GATA-1 mRNA was induced by most mutants and may contribute to differentiation. Because the GATA-1 C-terminal finger could bind its target site but not transactivate a minimal reporter, it may direct megakaryocytic maturation by derepressing specific genes and/or by interacting with another protein which provides the transactivation function.

Development of hematopoietic cells lacking transcription factor GATA-1

GATA-1 is a zinc-finger transcription factor believed to play an important role in gene regulation during the development of erythroid cells, megakaryocytes and mast cells. Other members of the GATA family, which can bind to the same DNA sequence motif, are co-expressed in several of these hemopoietic lineages, raising the possibility of overlap in function. To examine the specific roles of GATA-1 in hematopoietic cell differentiation, we have tested the ability of embryonic stem cells, carrying a targeted mutation in the X-linked GATA-1 gene, to contribute to various blood cell types when used to produce chimeric embryos or mice. Previously, we reported that GATA-1- mutant cells failed to contribute to the mature red blood cell population, indicating a requirement for this factor at some point in the erythroid lineage (L. Pevny et al., (1991) Nature 349, 257–260). In this study, we have used in vitro colony assays to identify the stage at which mutant erythroid cells are affected, and to examine the requirement for GATA-1 in other lineages. We found that the development of erythroid progenitors in embryonic yolk sacs was unaffected by the mutation, but that the cells failed to mature beyond the proerythroblast stage, an early point in terminal differentiation. GATA-1- colonies contained phenotypically normal macrophages, neutrophils and megakaryocytes, indicating that GATA-1 is not required for the in vitro differentiation of cells in these lineages. GATA-1- megakaryocytes were abnormally abundant in chimeric fetal livers, suggesting an alteration in the kinetics of their formation or turnover. The lack of a block in terminal megakaryocyte differentiation was shown by the in vivo production of platelets expressing the ES cell-derived GPI-1C isozyme. The role of GATA-1 in mast cell differentiation was examined by the isolation of clonal mast cell cultures from chimeric fetal livers. Mutant and wild-type mast cells displayed similar growth and histochemical staining properties after culture under conditions that promote the differentiation of cells resembling mucosal or serosal mast cells. Thus, the mast and megakaryocyte lineages, in which GATA-1 and GATA-2 are co-expressed, can complete their maturation in the absence of GATA-1, while erythroid cells, in which GATA-1 is the predominant GATA factor, are blocked at a relatively early stage of maturation.

Microcytic anemia in mk/mk mice is not corrected by retroviral-mediated gene transfer of wild-type p45 NF-E2

Mice homozygous for the mk mutation have a severe hypochromic, microcytic anemia that is characterized by a decreased mean-corpuscular hemoglobin concentration and balanced alpha- and beta-globin-chain synthesis. Transplantation studies have shown that the defect in homozygous mk/mk mice is intrinsic to both the hematopoietic system and the gut. The gene for the hematopoietic-specific transcription factor, p45 NF-E2, has been found to cosegregate with the mk phenotype and contain a point mutation in mk/mk mice that results in an amino acid substitution (173V-->A). In order to test the hypothesis that this amino acid substitution is responsible for the mk phenotype, we have used recombinant retroviruses to introduce wild-type p45 NF-E2 into the bone marrow of mk/mk mice. Despite gene transfer and expression of p45 NF-E2 in erythroid cells, we found no evidence for correction of the phenotype in mk/mk mice. These results indicate that the mk mutation cannot be corrected by enforced expression of wild-type p45 NF-E2 and suggest that the 173V-->A mutation of the p45 NF-E2 gene is not the cause of anemia in mk/mk mice.

Hematopoietic development of vav-/- mouse embryonic stem cells

The vav protooncogene product is expressed nearly exclusively in hematopoietic lineages and contains several structural motifs (SH2/SH3 domains and a dbl-oncogene homology region) typical of proteins functioning in signaling pathways. To ascertain if vav expression is required for hematopoiesis we generated vav-negative mouse embryonic stem cells by gene targeting and examined the consequences of loss of vav function on erythroid and myeloid development in vitro and in vivo. In conflict with the conclusions drawn from expression of antisense vav RNA in embryonic stem cells [Wulf, G. M., Adra, C. N. & Lim, B. (1993) EMBO J. 12, 5065-5074], we observed erythroid and myeloid development in the absence of vav. These experiments demonstrate that vav expression is not absolutely required for hematopoietic development.

An early haematopoietic defect in mice lacking the transcription factor GATA-2

Blood cell development relies on the expansion and maintenance of haematopoietic stem and progenitor cells in the embryo. By gene targeting in mouse embryonic stem cells, we demonstrate that the transcription factor GATA-2 plays a critical role in haematopoiesis, particularly of an adult type. We propose that GATA-2 regulates genes controlling growth factor responsiveness or the proliferative capacity of early haematopoietic cells.

Sequence-specific DNA binding of individual cut repeats of the human CCAAT displacement/cut homeodomain protein

CCAAT displacement protein (CDP), a nuclear protein of 180-190 kDa, contains a triplicated motif, the cut domain, similar (80-90% conserved) to three repeats of 60-65 amino acids first identified in Drosophila cut, a homeo-domain protein involved in cell-fate decisions in development. Cut repeats bind DNA and exhibit subtle differences in target-site recognition. DNA sequences specifically bound by cut repeats were isolated by PCR-mediated DNA target-site selection. Sequences selected for cut repeat 2 and 3 (CR2 and CR3) binding are A+T-rich and favor an ATA motif with similar, but not identical, flanking base preferences. CR2 and CR3 discriminate among similar target sequences. CR1, which is more divergent from CR2 and CR3, displays the most restricted pattern of DNA sequence recognition. Methylation interference analysis demonstrates different protein-DNA contacts for CR1 and CR3 binding to a target sequence. Thus, CDP/cut is a complex protein whose DNA-binding properties reflect the combinatorial interaction of four domains (three cut repeats and one homeodomain) with target DNA sequences.

Phosphorylation of the erythroid transcription factor GATA-1

GATA-1 is a zinc finger DNA-binding protein thought to be involved in the expression of the vast majority of erythroid specific genes. We have examined the phosphorylation of GATA-1 in murine erythroleukemia (MEL) cells and have mapped the sites of phosphorylation by overexpression of GATA-1 in monkey kidney COS cells. We show that GATA-1 is phosphorylated on 6 serines within its amino terminus in uninduced MEL cells and that a 7th site, serine 310, becomes phosphorylated after MEL cells are induced to differentiate by exposure to dimethyl sulfoxide. This site lies near the carboxyl boundary of the DNA-binding domain in a conserved region of the protein believed to be involved in DNA bending. Detailed analyses indicate, however, that phosphorylation at this site, or the other sites identified, does not significantly influence DNA-binding affinity or specificity, DNA bending, or transcriptional transactivation by GATA-1.

Regulation of the erythroid Kruppel-like factor (EKLF) gene promoter by the erythroid transcription factor GATA-1

Erythroid Kruppel-like factor (EKLF) is an erythroid-specific transcription factor that binds a CACCC motif found in the human beta-globin gene promoter. We have studied the promoter of the EKLF gene and identified binding sites for the transcription factors GATA-1 and CCAAT-binding Protein 1 (CP1). We show that both types of binding sites are required for full activity, and that the GATA motif at -60 is essential. The EKLF promoter can be directly activated in nonerythroid cells in cotransfection experiments by forced expression of GATA-1. These results suggest that EKLF is dependent on GATA-1 for its expression and lies downstream of, or coincident with, GATA-1 in a regulatory hierarchy in erythroid development.

Novel insights into erythroid development revealed through in vitro differentiation of GATA-1 embryonic stem cells

Mouse embryonic stem (ES) cells lacking the transcription factor GATA-1 do not produce mature red blood cells either in vivo or in vitro. To define the consequences of GATA-1 loss more precisely, we used an in vitro ES cell differentiation assay that permits enumeration of primitive (EryP) and definitive (EryD) erythroid precursors and recovery of pure erythroid colonies. In contrast to normal ES cells, GATA-1- ES cells fail to generate EryP precursors. EryD precursors, however, are normal in number but undergo developmental arrest and death at the proerythroblast stage. Contrary to initial expectations, arrested GATA-1(-)-definitive proerythroblasts express GATA target genes at normal levels. Transcripts of the related factor GATA-2 are remarkably elevated in GATA-1- proerythroblasts. These findings imply substantial interchangeability of GATA factors in vivo and suggest that GATA-1 normally serves to repress GATA-2 during erythropoiesis. The approach used here is a paradigm for the phenotypic analysis of targeted mutations affecting hematopoietic development.

Transcriptional control of erythropoiesis

Over the past year, substantial progress was made toward understanding transcriptional control of red cell differentiation. Complementary DNAs encoding two novel erythroid-restricted transcription factors--globin locus control region regulatory factor NF-E2 and CACC-binding protein EKLF--were cloned and characterized. Other DNA-binding activities have been implicated in developmental regulation of hemoglobin expression; these are postulated to mediate competitive interactions between globin gene promoters. As individual transcriptional regulatory factors are better understood, attention must turn to how they interact among themselves and with other proteins to initiate and maintain the erythroid program.

Infrequent mutation of the WT1 gene in 77 Wilms' Tumors

Homozygous deletions in Wilms' tumor DNA have been a key step in the identification and isolation of the WT1 gene. Several additional loci are also postulated to contribute to Wilms' tumor formation. To assess the frequency of WT1 alterations we have analyzed the WT1 locus in a panel of 77 Wilms' tumors. Eight tumors showed evidence for large deletions of several hundred or thousand kilobasepairs of DNA, some of which were also cytogenetically detected. Additional intragenic mutations were detected using more sensitive SSCP analyses to scan all 10 WT1 exons. Most of these result in premature stop codons or missense mutations that inactivate the remaining WT1 allele. The overall frequency of WT1 alterations detected with these methods is less than 15%. While some mutations may not be detectable with the methods employed, our results suggest that direct alterations of the WT1 gene are present in only a small fraction of Wilms' tumors. Thus, mutations at other Wilms' tumor loci or disturbance of interactions between these genes likely play an important role in Wilms' tumor development.

The ubiquitous subunit of erythroid transcription factor NF-E2 is a small basic-leucine zipper protein related to the v-maf oncogene

Erythroid transcription factor NF-E2 is a tissue-restricted heterodimeric protein which recognizes an extended AP-1 motif [(T/C)TGCTGA(C/G)TCA(T/C)] found in the upstream locus control regions of the alpha- and beta-globin gene clusters. A cDNA clone encoding a cell-type-specific subunit of NF-E2, designated p45 NF-E2, has previously been characterized and shown to encode a basic-leucine zipper DNA-binding protein. Here we describe protein purification and cloning of cDNA that encodes the second basic-leucine zipper subunit of the native NF-E2 heterodimer. This polypeptide, designated p18, is widely expressed. It displays extensive homology to the v-maf oncogene product and a human retinal-specific protein, NRL. Unusual features in the basic region shared by v-Maf, NRL, and p18 place them in a distinct subfamily of AP-1-like proteins.

Gene targeting of X chromosome-linked chronic granulomatous disease locus in a human myeloid leukemia cell line and rescue by expression of recombinant gp91phox

The X chromosome-linked chronic granulomatous disease (X-CGD) locus, which encodes the gp91phox subunit of the phagocyte respiratory-burst oxidase cytochrome b, was disrupted by homologous recombination in the PLB-985 human myeloid cell line to develop an in vitro model of X-CGD. Superoxide formation was absent in targeted cells after differentiation to granulocytes but was rescued by stable transfection and expression of wild-type gp91phox cDNA. The targeted cell line should be useful in experiments aimed at defining functional regions within gp91phox by expression of mutant gp91phox cDNAs, complementing studies of naturally occurring mutations in X-CGD. In addition, the mutant line provides a model system in which to establish an experimental basis for the treatment of X-CGD patients with gene replacement therapy. Rescued clones containing even modest amounts of recombinant gp91phox had respiratory-burst activity comparable to the wild-type PLB-985 line, suggesting that functional correction of X-CGD neutrophils may not require high-level expression of gp91phox.

Long-term in vivo expression of a murine adenosine deaminase gene in rhesus monkey hematopoietic cells of multiple lineages after retroviral mediated gene transfer into CD34+ bone marrow cells

Retroviral mediated gene transfer into stem cells has been proposed as therapy for many inherited hematopoietic diseases. Deficiency of the enzyme adenosine deaminase (ADA) results in depletion of T lymphocytes, causing severe combined immunodeficiency syndrome (SCIDS). In this report, we describe retroviral mediated gene transfer of a murine ADA cDNA into Rhesus monkey hematopoietic stem cells. Immunoselected CD34+ bone marrow cells were exposed to medium containing the ADA retrovirus during culture on a stromal cell line engineered to express the transmembrane form of stem cell factor. After infusion of autologous, transduced cells into irradiated recipients, gene transfer was observed in all three monkeys. The ADA provirus was detected in 2% of circulating granulocytes and T cells from 100 days post-transplantation to longer than 1 year and in B cells from 250 days post-transplantation and beyond. Mouse ADA activity was detected in peripheral blood cells at approximately 3% the activity of monkey ADA. Thus, we have shown gene transfer into repopulating cells that contribute to all hematopoietic lineages with persistent gene expression. These data provide support for the use of stem cell targeted gene transfer for therapy of ADA deficiency.

Purification of the human NF-E2 complex: cDNA cloning of the hematopoietic cell-specific subunit and evidence for an associated partner

The human globin locus control region-binding protein, NF-E2, was purified by DNA affinity chromatography. Its tissue-specific component, p45 NF-E2, was cloned by use of a low-stringency library screen with murine p45 NF-E2 cDNA (N. C. Andrews, H. Erdjument-Bromage, M. B. Davidson, P. Tempst, and S. H. Orkin, Nature [London] 362:722-728, 1993). The human p45 NF-E2 gene was localized to chromosome 12q13 by fluorescent in situ hybridization. Human p45 NF-E2 and murine p45 NF-E2 are highly homologous basic region-leucine zipper (bZIP) proteins with identical DNA-binding domains. Immunoprecipitation experiments demonstrated that p45 NF-E2 is associated in vivo with an 18-kDa protein (p18). Because bZIP proteins bind DNA as dimers, we infer that native NF-E2 must be a heterodimer of 45- and 18-kDa subunits. Although AP-1 and CREB copurified with NF-E2, no evidence was found for heterodimer formation between p45 NF-E2 and proteins other than p18. Thus, p18 appears to be the sole specific partner of p45 NF-E2 in erythroid cells. Cloning of human p45 NF-E2 should permit studies of the role of NF-E2 in globin gene regulation and erythroid differentiation.

Loss of erythropoietin responsiveness in erythroid progenitors due to expression of the Evi-1 myeloid-transforming gene

Inappropriate expression of the Evi-1 zinc-finger gene in hematopoietic cells has been associated with acute myelogenous leukemia and myelodysplastic syndromes in murine models and in humans. Consistent with this, previous studies have shown that aberrant expression of the Evi-1 gene in a myeloid progenitor cell line blocks granulocytic differentiation. Here we demonstrate that the aberrant expression of the Evi-1 gene impairs the normal response of erythroid cells or bone-marrow progenitors to erythropoietin. Erythroid differentiation has been shown to require the GATA-1 transcription factor that binds to a sequence contained within the consensus binding sequence identified for Evi-1. In the studies presented here we also show that Evi-1 can repress GATA-1-dependent transactivation in transient chloramphenicol acetyltransferase assays. Together the data support the hypothesis that inappropriate expression of the Evi-1 gene blocks erythropoiesis by repressing the transcription of a subset of GATA-1 target genes.

DNA-binding specificity of GATA family transcription factors

GATA-binding proteins constitute a family of transcription factors that recognize a target site conforming to the consensus WGATAR (W = A or T and R = A or G). Here we have used the method of polymerase chain reaction-mediated random site selection to assess in an unbiased manner the DNA-binding specificity of GATA proteins. Contrary to our expectations, we show that GATA proteins bind a variety of motifs that deviate from the previously assigned consensus. Many of the nonconsensus sequences bind protein with high affinity, equivalent to that of conventional GATA motifs. By using the selected sequences as probes in the electrophoretic mobility shift assay, we demonstrate overlapping, but distinct, sequence preferences for GATA family members, specified by their respective DNA-binding domains. Furthermore, we provide additional evidence for interaction of amino and carboxy fingers of GATA-1 in defining its binding site. By performing cotransfection experiments, we also show that transactivation parallels DNA binding. A chimeric protein containing the finger domain of areA and the activation domains of GATA-1 is capable of activating transcription in mammalian cells through GATA motifs. Our findings suggest a mechanism by which GATA proteins might selectively regulate gene expression in cells in which they are coexpressed.

Expression of mRNA for the GATA-binding proteins in human eosinophils and basophils: potential role in gene transcription

The expression of the hematopoietic transcription factors GATA-1, GATA-2, and GATA-3 was studied in eosinophils and basophils. Eosinophils express mRNA for GATA-1, GATA-2, and GATA-3. Basophils express GATA-2 and GATA-3. Treatment of HL-60 eosinophilic sublines with either interleukin-5 or butyric acid increased the expression of GATA-1 mRNA concomitant with the expression of eosinophil-specific genes, whereas levels of GATA-2 mRNA remained relatively constant. The presence of mRNA for these proteins in eosinophils and basophils suggests that gene transcription in these lineages may be regulated by GATA-binding proteins.

Mouse microcytic anaemia caused by a defect in the gene encoding the globin enhancer-binding protein NF-E2

The nuclear DNA-binding protein NF-E2 is thought to mediate the powerful erythroid enhancer activity of the alpha- and beta-globin locus control regions and participates in the control of genes encoding two enzymes of haem biosynthesis (porphobilinogen deaminase and ferrochelatase). The major component of NF-E2 is a 45K polypeptide (designated p45 NF-E2) that belongs to the basic region-leucine zipper family of transcription factors. This subunit of NF-E2 is specifically expressed in haematopoietic progenitor cells and differentiated cells of the erythroid, megakaryocyte and mast cell lineages. The gene encoding p45 NF-E2 (murine gene Nfe2) has been mapped to mouse chromosome 15 near the mutation microcytosis (mk). Homozygous mk mice have severe hypochromic microcytic anaemia as a result of decreased globin synthesis and defects in intestinal and erythroid iron absorption. Here we investigate whether the mk mutation lies within Nfe2 by characterizing the p45 NF-E2 gene and determining its DNA sequence in wild-type and mk alleles. The mk allele carries a missense mutation that causes substitution of valine by alanine at amino acid 173 of the p45 NF-E2 protein. Expression of p45 NF-E2 messenger RNA was detected in erythroid tissues of normal mice and in the duodenum of normal and severely anaemic beta-thalassaemic (Hbbd-th3/Hbbd-th3) mice. We propose that the mk mutation results in an impaired form of NF-E2 which fails to regulate both globin production and iron metabolism properly.

Erythroid transcription factor NF-E2 is a haematopoietic-specific basic-leucine zipper protein

Expression of globin genes in developing erythroid cells is controlled by upstream locus control regions. Activity of these regions in vivo requires an erythroid-specific nuclear factor (NF-E2) that binds AP-1-like recognition sites. Its tissue-specific component (p45 NF-E2) has been characterized by complementary DNA cloning as a new basic region-leucine zipper protein which dimerizes with a ubiquitous partner to form native NF-E2.

Regulation of the beta-globin locus

Transcription of the human beta-globin gene cluster depends upon upstream regulatory sequences, which are collectively termed the locus control region. Recent studies have provided new insights into how the individual genes of the cluster are regulated through development. The crux of transcriptional activation is how the locus control region communicates with the gene-proximal regulatory elements.

Mouse GATA-4: a retinoic acid-inducible GATA-binding transcription factor expressed in endodermally derived tissues and heart

We report the cDNA cloning and characterization of mouse GATA-4, a new member of the family of zinc finger transcription factors that bind a core GATA motif. GATA-4 cDNA was identified by screening a 6.5-day mouse embryo library with oligonucleotide probes corresponding to a highly conserved region of the finger domains. Like other proteins of the family, GATA-4 is approximately 50 kDa in size and contains two zinc finger domains of the form C-X-N-C-(X17)-C-N-X-C. Cotransfection assays in heterologous cells demonstrate that GATA-4 trans activates reporter constructs containing GATA promoter elements. Northern (RNA) analysis and in situ hybridization show that GATA-4 mRNA is expressed in the heart, intestinal epithelium, primitive endoderm, and gonads. Retinoic acid-induced differentiation of mouse F9 cells into visceral or parietal endoderm is accompanied by increased expression of GATA-4 mRNA and protein. In vitro differentiation of embryonic stem cells into embryoid bodies is also associated with increased GATA-4 expression. We conclude that GATA-4 is a tissue-specific, retinoic acid-inducible, and developmentally regulated transcription factor. On the basis of its tissue distribution, we speculate that GATA-4 plays a role in gene expression in the heart, intestinal epithelium, primitive endoderm, and gonads.

The SCL gene product: a positive regulator of erythroid differentiation

The SCL (tal-1, TCL5) gene is a member of the basic domain, helix-loop-helix (bHLH) class of putative transcription factors. We found that (i) the SCL promoter for exon Ia contains a potential recognition site for GATA-binding transcription factors, (ii) SCL mRNA is expressed in all erythroid tissues and cell lines examined, and (iii) SCL mRNA increases upon induced differentiation of murine erythroleukemia (MEL) cells, and inferred that SCL may play a physiologic role in erythroid differentiation. We used gel shift and transfection assays to demonstrate that the GATA motif in the SCL promoter binds GATA-1 (and GATA-2), and also mediates transcriptional transactivation. To identify a role for SCL in erythroid differentiation, we generated stable transfectants of MEL and K562 (a human chronic myelogenous leukemia cell line that can differentiate along the erythroid pathway) cells overexpressing wild-type, antisense or mutant SCL cDNA. Increasing the level of SCL expression in two independent MEL lines (F4-6 and C19, a 745 derivative) and K562 cells increased the rate of spontaneous (i.e. in the absence of inducer) erythroid differentiation. Conversely, induced differentiation was inhibited in MEL transfectants expressing either antisense SCL cDNA or a mutant SCL lacking the basic domain. Our experiments suggest that the SCL gene can be a target for the erythroid transcription factor GATA-1 and that the SCL gene product serves as a positive regulator of erythroid differentiation.

Splice site mutations are a common cause of X-linked chronic granulomatous disease

Chronic granulomatous disease (CGD) is characterized by the absence of a respiratory burst in activated phagocytes. Defects in at least four different genes lead to CGD. Patients with the X-linked form of CGD have mutations in the gene for the beta-subunit of cytochrome b558 (gp91-phox). We studied the molecular defect in four patients with X-linked CGD. In a fifth family, we studied the mother of a patient with X-linked CGD who had died before our investigations. Gp91-phox messenger RNA (mRNA) was reverse transcribed into cDNA and the coding region was amplified by polymerase chain reaction into three fragments. Sequence analysis showed the absence of the exon 7, 5, 3, and 2 sequences in patients 1, 2, 3, and 4, respectively. In carrier 5, we found both normal cDNA and cDNA that lacked 57 3'-nucleotides of exon 6. We analyzed the splice sites of the flanking introns of the missing exons. In patients 1, 2, and 3, we found single nucleotide substitutions within the first five positions of the down-stream 5' donor splice sites. In patient 4, a similar substitution was found at position -1 of the 3' acceptor splice site of intron 1. In carrier 5, no mutation was found in the exon 6-intron 6 boundary sequence. Instead, a single substitution was observed in exon 6 (C----A at nucleotide 633) that created a new donor splice site. Apparently, mRNA splicing occurs preferentially at this newly created splice site. We conclude that the absence of the exon sequences in the gp91-phox mRNA of these patients is due to splicing errors. Of 30 European X-linked CGD patients studied by us so far, five appear to be caused by mutations that affect correct mRNA splicing. Thus, such mutations appear to be a common cause of X-linked CGD.

Cell cycle-dependent initiation and lineage-dependent abrogation of GATA-1 expression in pure differentiating hematopoietic progenitors

The programmed activation/repression of transcription factors in early hematopoietic differentiation has not yet been explored. The DNA-binding protein GATA-1 is required for normal erythroid development and regulates erythroid-expressed genes in maturing erythroblasts. We analyzed GATA-1 expression in early human adult hematopoiesis by using an in vitro system in which "pure" early hematopoietic progenitors are induced to gradual and synchronized differentiation selectively along the erythroid or granulocyte-macrophage pathway by differential treatment with hematopoietic growth factors. The GATA-1 gene, though virtually silent in quiescent progenitors, is activated after entrance into the cell cycle upon stimulation with hematopoietic growth factors. Subsequently, increasing expression along the erythroid pathway contrasts with an abrupt downregulation in the granulocyte-macrophage lineage. These results suggest a microenvironment-directed, two-step model for GATA-1 expression in differentiating hematopoietic progenitors that involves (i) cycle-dependent initiation and (ii) lineage-dependent maintenance or suppression. Hypothetically, on/off switches of lineage-restricted transactivators may underlie the binary fate decisions of hematopoietic progenitors.

In vivo protein-DNA interactions at hypersensitive site 3 of the human beta-globin locus control region

The expression of beta-globin genes in developing erythroid cells is dependent on distant, upstream regulatory sequences, known as the locus control region (LCR), which are marked in chromatin by DNase I hypersensitive sites (HS-1 to HS-4). Linkage of the beta-globin gene complex LCR or fragments surrounding core regions of 200-300 base pairs to the human beta-globin gene permits consistent, high-level expression of the transgene in mice. To define the array of nuclear factors interacting with beta-LCR HS-3, we have performed in vivo dimethyl sulfate footprinting of the active HS-3 core in erythroid cells by a modified procedure that permits assessment of protein-DNA contacts at adenine, as well as guanine, residues. In vivo protein occupancy differs considerably from that predicted from previous in vitro binding analyses. In vivo footprinting detects protein binding at four sites recognized by the erythroid transcription factor GATA-1, at two CACC/GT motifs, and at a single AP-1/NF-E2 site. The regulatory elements occupied in vivo in HS-3 appear similar to those described previously in globin gene promoters and 3' enhancers. These findings suggest that the distinctive properties of the HS-3 region may be attributable to the organization of these occupied motifs and the consequent protein interactions, rather than to the binding of unique LCR regulatory factors.

In vivo footprinting of the human alpha-globin locus upstream regulatory element by guanine and adenine ligation-mediated polymerase chain reaction

A major regulatory element required for expression of the human alpha-globin genes is located 40 kb upstream of the embryonic zeta-globin gene. To understand how this and other locus control region (LCR) elements contribute to high-level expression in erythroid cells, we have performed high-resolution, in vivo dimethyl sulfate footprinting. In addition, we have modified the dimethyl sulfate-based ligation-mediated polymerase chain reaction in vivo footprinting procedure to permit the assessment of interactions at guanine and adenine residues, rather than guanines alone. In vivo footprinting of the human alpha-LCR element carried on chromosome 16 in a mouse erythroleukemia cell environment revealed protein occupancy at GATA-1, AP-1/NF-E2, and CACC/GGTGG motifs, specific differences compared with in vitro protein binding, and distinct changes in one region upon dimethyl sulfoxide-induced cellular maturation. No protein contacts were detected in nonexpressing hepatoma cells. In addition, we have demonstrated that two AP-1 motifs in the alpha-LCR element which are occupied in vivo bind purified mouse NF-E2 protein in vitro. Our data suggest that three proteins, GATA-1, NF-E2, and unknown CACC/GGTGG factors, are minimally required as DNA-binding proteins for the function of LCR-like elements. The juxtaposition and interaction of these factors with each other, and with accessory proteins not directly in contact with DNA, are likely to account for the relative position independence of the upstream globin regulatory elements.

Rescue of erythroid development in gene targeted GATA-1- mouse embryonic stem cells

Development of definitive (fetal liver-derived) red cells is blocked by a targeted mutation in the gene encoding the transcription factor GATA-1. We used in vitro differentiation of GATA-1- mouse embryonic stem (ES) cells to reveal a requirement for GATA-1 during primitive (yolk sac-derived) erythropoiesis and to establish a rescue assay. We show that the block to development includes primitive, as well as definitive, erythroid cells and is complete at the level of globin RNA expression; that the introduction of a normal GATA-1 gene restores developmental potential both in vivo and in vitro; and that efficient rescue is dependent on a putative autoregulatory GATA-motif in the distal promoter. Use of in vitro differentiated ES cells bridges a gap between conventional approaches to gene function in cell lines and analysis of loss of function mutations in the whole animal.

Sequence of the human GATA-1 promoter

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Human CCAAT displacement protein is homologous to the Drosophila homeoprotein, cut

Human CCAAT displacement protein (CDP), a putative repressor of developmentally regulated gene expression, was purified from HeLa cells by DNA binding-site affinity chromatography. cDNA encoding CDP was obtained by immunoscreening a lambda gt11 library with antibody raised against purified protein. The deduced primary amino acid sequence of CDP reveals remarkable homology to Drosophila cut with respect to the presence of a unique homeodomain and "cut repeats". As cut participates in determination of cell fate in several tissues in Drosophila, the similarity predicts a broad role for CDP in mammalian development.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) encompasses a group of rare inherited disorders characterized by defects in a phagocyte-specific NADPH-oxidase complex that forms the superoxide radical during the respiratory burst. In this chapter, the protein components and cellular biochemistry of the oxidase are reviewed in light of recent genetic and biochemical studies of CGD. The classification and molecular genetic analysis of CGD is discussed. Finally, the use of recombinant human interferon-gamma as a new therapeutic agent for management of the disorder is reviewed.

Human transcription factor GATA-2. Evidence for regulation of preproendothelin-1 gene expression in endothelial cells

Previously, we showed that the promoter of the gene encoding preproendothelin-1 (PPET-1) contains a GATA motif that is essential for activity and interacts with a nuclear factor similar in size and binding specificity to the erythroid transcription factor GATA-1. To identify this endothelial GATA-binding protein, a human endothelial cell cDNA library was screened with oligonucleotide probes for a portion of the zinc finger domain of GATA-1. A 2.6-kilobase cDNA encoding a 470 amino acid protein was obtained. Sequence analysis revealed a predicted protein which is the human counterpart of a related chicken protein, designated GATA-2. Human GATA-2 is expressed by a variety of cells, including erythroid, HeLa, and endothelial cells. A complex of a GATA-containing probe and recombinant GATA-2 expressed in COS cells comigrates with that present in gel shift experiments with nuclear extract derived from endothelial cells. In addition, expressed human GATA-2 protein transactivates reporter gene constructs containing either minimal GATA promoter elements or the native PPET-1 promoter in a cotransfection assay. Retinoic acid treatment of endothelial cells results in down-regulation of GATA-2 expression as well as down-regulation of PPET-1 gene expression. Human homologs of other known GATA-binding transcription factors are either absent from endothelial cells (in the case of GATA-1) or made in small quantities and not significantly affected by retinoid acid in these cells (in the case of GATA-3), making it unlikely that they regulate the PPET-1 gene. We propose that GATA-2 is the GATA-binding protein required for PPET-1 gene expression in endothelial cells.

Point mutation in the cytoplasmic domain of the neutrophil p22-phox cytochrome b subunit is associated with a nonfunctional NADPH oxidase and chronic granulomatous disease

Chronic granulomatous disease (CGD) is a congenital disorder in which phagocytes cannot generate superoxide (O2-) and other microbial oxidants due to mutations in any one of four components of the O2(-)-generating complex, NADPH oxidase. We report here a female CGD patient in whom a missense mutation in one of these components, the p22-phox subunit of the neutrophil membrane cytochrome b [where phox indicates phagocyte oxidase (used to designate protein components of the phagocyte NADPH oxidase)] results in a nonfunctional oxidase and failure of neutrophils to produce O2- in response to phorbol 12-myristrate 13-acetate. Cytochrome b in the patient's neutrophils was normal in appearance and abundance as determined by visible spectroscopy and by immunoblots of the gp91 and p22 subunits. However, the neutrophil plasma membranes were devoid of activity in the cell-free oxidase activation system, whereas the cytosol functioned normally. We postulated that the patient was homozygous for a mutation in p22 that results in the synthesis of normal levels of a nonfunctional cytochrome b. A single-base substitution (C----A) was found in the patient's mononuclear cell p22-phox cDNA that predicts a nonconservative Pro----Gln substitution at residue 156. The same mutation was also identified in all clones sequenced from patient genomic DNA, demonstrating homozygosity for the mutant allele. An antipeptide antibody against p22 residues 153-164 was found to bind only to permeabilized neutrophils, indicating that the mutation occurs in a cytoplasmic domain. These studies establish that this domain of p22-phox is cytoplasmic and that mutations in this region can have profound effects on cytochrome b function.

GATA-binding transcription factors in mast cells regulate the promoter of the mast cell carboxypeptidase A gene

The transcription factors GATA-1, GATA-2, and GATA-3 were found to be expressed in several mouse and rat mast cell lines that contain mast cell carboxypeptidase A (MC-CPA) and other proteases in their cytoplasmic granules. GATA-1 mRNA was not detected in P815 cells, an immature mouse mastocytoma-derived cell line that lacks electron-dense granules and has low levels of secretory granule proteases. Because the 5'-flanking regions of the mouse and human MC-CPA genes contained a conserved GATA-binding motif 51 base pairs upstream of their translation initiation sites, the ability of GATA-binding proteins to regulate the promoter activity of the MC-CPA gene was examined in rat basophilic leukemia cells, mouse P815 cells, and transfected mouse P815 cells that expressed GATA-1. In all three mast cell lines, the promoter activity of the MC-CPA gene depended on the GATA binding site. GATA-1, GATA-2, and GATA-3 are thus the first DNA-binding proteins identified in mast cells which regulate the promoter activity of a gene that encodes a secretory granule protease.

Expression of GATA-binding proteins during embryonic development in Xenopus laevis

Proteins that recognize the core sequence GATA are important regulators of hematopoietic-specific gene transcription. We have characterized cDNAs encoding the Xenopus laevis homologues of three related transcription factors, designated GATA-1, -2, and -3. Comparative sequence analysis reveals strong conservation of the zinc-finger DNA-binding domain among all vertebrate GATA-binding proteins. GATA-2 and GATA-3 polypeptides are homologous throughout their entire sequences, whereas GATA-1 sequence is conserved only in the region responsible for DNA binding. In Xenopus, RNAs encoding GATA-binding proteins are expressed in both larval and adult erythroid cells. GATA-1, -2, and -3 RNAs are first detectable in early gastrula (Nieuwkoop developmental stage 11). This is earlier than the appearance of the early larval alpha T1 globin RNA (stage 15), beta T1 globin RNA (stage 26), or blood island formation (stage 30). The expression of GATA-1, -2, and -3 in early development may signal an early commitment of mesoderm to form hematopoietic tissue.

Activation of the erythropoietin receptor promoter by transcription factor GATA-1

Erythropoietin, a glycoprotein produced by the kidneys in response to anemia and hypoxia, is a major growth factor for cells of the erythroid lineage. Erythropoietin interacts with high-affinity cell surface receptors (EpoR) present on developing progenitors and is required for their survival. Previously we characterized the gene for EpoR and demonstrated that its promoter acts in a cell-specific manner. Here we show that the hematopoietic-specific transcription factor GATA-1 is necessary, and indeed is sufficient as the sole cell-restricted regulator, for activation of the EpoR promoter in fibroblast transfection assays. Hence, GATA-1, which participates in transcriptional control of the majority of erythroid-expressed genes, also acts on the promoter of an essential lineage-restricted receptor (EpoR). This central contribution of GATA-1 to EpoR promoter function provides a mechanism whereby a cell-restricted regulator may ensure the viability and subsequent maturation of progenitor cells during hematopoietic differentiation.

Targeting of transgene expression to monocyte/macrophages by the gp91-phox promoter and consequent histiocytic malignancies

A component of a heterodimeric cytochrome b, designated gp91-phox, is required for the microbicidal activity of phagocytic cells and is expressed exclusively in differentiated myelomonocytic cells (granulocytes; monocyte/macrophages). In an attempt to identify cis-elements responsible for this restricted pattern of expression, we produced transgenic mice carrying reporter genes linked to the human gp91-phox promoter. Immunohistochemical and RNA analyses indicate that 450 base pairs of the proximal gp91-phox promoter is sufficient to target reporter expression to a subset of monocyte/macrophages. Mice expressing simian virus 40 large tumor antigen under control of the gp91-phox promoter develop monocyte/macrophage-derived malignancies with complete penetrance at 6-12 mo of age and provide an animal model of true histiocytic lymphoma. As these transgenes are inactive in most phagocytic cells that express the endogenous gp91-phox-encoding gene, we infer that additional genomic regulatory elements are necessary for appropriate targeting to the full complement of phagocytes in vivo.

CCAAT displacement protein as a repressor of the myelomonocytic-specific gp91-phox gene promoter

The cytochrome b heavy chain (gp91-phox) is expressed exclusively in terminally differentiating myelomonocytic cells. The human gp91-phox gene spans approximately 30 kilobases, and is divided into 13 exons. A ubiquitous factor that is indistinguishable from the CCAAT-binding factor CP1 interacts in vitro with the distal gp91-phox promoter CCAAT box motif. CP1 binding is prevented, however, by a CCAAT displacement protein (CDP) that binds to the region surrounding the CCAAT box. CDP DNA-binding activity is found in nuclear extracts prepared from cells in which the endogenous gp91-phox gene is transcriptionally inactive, but is absent or reduced in expressing cells, consistent with CDP functioning as a repressor of gp91-phox transcription. Introduction of gp91-phox promoter/reporter constructs into nonexpressing cells yields significantly less expression than that produced by the parental reporter vector alone. The reduction in expression is relieved when the CDP/CP1-binding site is removed from the gp91-phox promoter, confirming that it is a target for repression. No derepression is observed if the CP1-binding site is selectively mutated. Derepression of expression exhibited upon deletion of the CDP/CP1-binding site suggests that, in addition to blocking the interaction of the CCAAT-binding factor with the gp91-phox promoter, CDP may also repress transcription mediated through a distinct cis-element(s). We propose that down-regulation of CDP DNA-binding activity is a necessary step in the induction of myelomonocytic-specific expression of the gp91-phox gene.

Restriction of neuroblastoma to the prostate gland in transgenic mice

Male transgenic mice that carry a construct containing 5'-flanking sequences of the gp91-phox gene linked to the early region of the simian virus 40 (SV40) genome reproducibly develop tumors arising from the prostate gland. As gp91-phox is expressed exclusively in terminally differentiating hematopoietic cells of the myelomonocytic lineage, the induction of tumors arising from the prostate gland was unexpected. These lesions appear to be due to a novel transcription signal that was generated during the construction of the transgene. Surprisingly, the histopathological and biochemical properties of the tumor are diagnostic of neuroblastoma rather than of adenocarcinoma of the prostate gland. Tumors produce SV40 T antigen and isoforms of neural cell adhesion molecule characteristic of neuronal cells, and they occur in a testosterone-independent manner. Microscopic examination of prostate glands from young transgenic mice reveals the presence of small lesions arising outside of the prostate gland epithelium, which is consistent with the diagnosis of neuroblastoma and further distinguishes this tumor from prostatic adenocarcinoma. Prostate gland tumors occur in all male animals of susceptible lines carrying the gp91-phox promoter/SV40 early-region transgene. However, variability in the time at which gross tumors appear and the presence of cells expressing T antigen prior to tumorigenesis suggest that somatic events in addition to T-antigen production are required for the development of a malignancy. The extraordinary restriction of the site of tumorigenesis in these animals indicates the presence in the prostate gland of a novel, tissue-specific neuroectodermal cell of origin. These transgenic animals provide a model system for the study of neuroectodermal malignancies.

Regulated expression of endothelin 1 in glomerular capillary endothelial cells

Endothelin (ET)-1 is a powerful vasoconstrictor known to be produced and secreted by endothelial cells lining large vessels. Because ET-1 stimulates glomerular mesangial cell contraction, glomerular capillary endothelial cells (GEN), normally situated in close apposition to mesangial cells, were examined for potential ET expression and secretion. Cultured bovine GEN released ET in a time-dependent fashion. ET secretion was significantly stimulated by bradykinin, an agonist known to activate phospholipase C in these cells. Preproendothelin 1 (preproET-1) mRNA levels in GEN rose in a biphasic manner on stimulation with bradykinin. The early increments (at 30 min) were not dependent on new protein synthesis, whereas the late rise (6 h after addition of bradykinin) appeared to be protein synthesis dependent. Neither early or late bradykinin-stimulated preproET-1 mRNA expression in glomerular endothelial cells was due to inhibition of mRNA breakdown. Both phases of preproET-1 mRNA expression were observed with other glomerular endothelial cell calcium-mobilizing agonists, namely thrombin, and were mimicked by the calcium ionophore ionomycin. By contrast, the protein kinase C activator phorbol myristate acetate only enhanced preproET-1 mRNA expression at 30 min and suppressed expression thereafter. It is concluded that GEN have the potential to express and secrete ET-1 in a phospholipase C-regulated fashion. Furthermore, because glomerular mesangial cells respond to this peptide, the findings raise the possibility of paracrine regulation of mesangial cell tone by glomerular endothelial cell-derived ET-1.

Functional analysis and in vivo footprinting implicate the erythroid transcription factor GATA-1 as a positive regulator of its own promoter

Transcription of erythroid-expressed genes and normal erythroid development in vivo are dependent on a regulatory protein (GATA-1) that recognizes a consensus GATA motif. GATA-1 expression is itself restricted to erythroid progenitors and to two related hematopoietic lineages, megakaryocytes and mast cells. During cellular maturation the levels of GATA-1 RNA and protein increase progressively. In an effort to delineate mechanisms by which this pivotal transcription factor is itself regulated we have characterized the mouse GATA-1 gene and cis-elements within its promoter. We find that the isolated promoter retains cell specificity exhibited by the intact gene. Full promoter activity requires the presence of proximal CACCC box sequences and an upstream, double GATA motif that binds a single GATA-1 molecule in an asymmetric fashion. Using in vivo footprinting of mouse erythroleukemic cells we detect protein binding in vivo to both cis-elements. On the basis of these findings we propose that a positive feedback loop mediated through GATA-1 serves two complementary functions: maintenance of the differentiated state by locking the promoter into an "on" state, and programming the progressive increase in protein content throughout cellular maturation.

Human GATA-3: a lineage-restricted transcription factor that regulates the expression of the T cell receptor alpha gene

In addition to its role in the recognition of foreign antigens, the T cell receptor (TCR) alpha gene serves as a model system for studies of developmentally-regulated, lineage-specific gene expression in T cells. TCR alpha gene expression is restricted to cells of the TCR alpha/beta+ lineage, and is controlled by a T cell-specific transcriptional enhancer located 4.5 kb 3' to the C alpha gene segment. The TCR alpha enhancer contains four nuclear protein binding sites called T alpha 1-T alpha 4. In this report we describe the identification and characterization of a novel human cDNA, hGATA-3 that binds to the T alpha 3 element of the human TCR alpha enhancer. hGATA-3 contains a zinc finger domain that is highly related to the DNA-binding domain of the erythroid-specific transcription factor, GATA-1, and binds to a region of T alpha 3 that contains a consensus GATA binding site (AGATAG). Northern blot analyses of hematopoietic cell lines demonstrate that hGATA-3 is expressed exclusively in T cells. Overexpression of hGATA-3 in HeLa cells or human B cells specifically activated transcription from a co-transfected reporter plasmid containing two copies of the T alpha 3 binding site located upstream of the minimal SV40 promoter. Taken together these results demonstrate that hGATA-3 is a novel lineage-specific hematopoietic transcription factor that appears to play an important role in regulating the T cell-specific expression of the TCR alpha gene.

Linkage of the erythroid transcription factor gene (Gf-1) to the proximal region of the X chromosome of mice

We have used a cDNA probe for mouse Gf-1 gene that encodes the erythroid cell transcription factor to identify genetic variation in genomic DNA between Mus species. The segregation of Gf-1 DNA variation was analyzed in Mus species crosses that have been previously typed for the segregation of more than 30 genes spanning 80 cM of the mouse X chromosome from the centromere to the border of the X-Y pairing region. We identified a single X chromosome locus in the mouse, Gf-1, and an analysis of recombinants from 203 backcross progeny mapped Gf-1 to the proximal portion of the chromosome, coincident with the Cybb locus and proximal to Otc gene locus. A gene order of centromere, DXWas70, Cybb/Gf-1, Otc, Timp was established for the mouse X chromosome, which is in agreement with the map position observed on the human X chromosome.

Restoration of phagocyte function by interferon-gamma in X-linked chronic granulomatous disease occurs at the level of a progenitor cell

Phagocytes from X-linked chronic granulomatous disease (X-CGD) patients are deficient in their ability to generate superoxide because of a defective gene that encodes a heavy chain of cytochrome b, a critical component in the superoxide-generating pathway. Previously we have shown that a single in vivo treatment of selected X-CGD patients with interferon-gamma (INF-gamma) resulted 14 days later in near-normal levels of superoxide generation by phagocytes. The effect persisted for 28 days. This prolonged effect suggested that the lymphokine affected progenitor cells. In this study, we examined progenitor-derived colonies from the peripheral blood from this unusual X-CGD kindred. Progenitor-derived colonies examined before treatment were unable to generate superoxide as visualized by lack of nitro blue tetrazolium (NBT) reduction compared with normal controls. By contrast, colonies derived 7 days after a single INF-gamma injection were able to generate superoxide as shown by increased NBT reduction. Colonies harvested 21 days after treatment contained only rare cells capable of NBT reduction. Our results indicate that INF-gamma can reprogram the myeloid progenitor cells to express a partially corrected phenotype. This corrected phenotype is later expressed in daughter cells.