Restoration of the CCAAT Box or Insertion of the CACCC Motif Activate δ-Globin Gene Expression

Engineering of the endogenous HBD promoter increases HbA2

The β-hemoglobinopathies, such as sickle cell disease and β-thalassemia, are one of the most common genetic diseases worldwide and are caused by mutations affecting the structure or production of β-globin subunits in adult hemoglobin. Many gene editing efforts to treat the β-hemoglobinopathies attempt to correct β-globin mutations or increase γ-globin for fetal hemoglobin production. δ-globin, the subunit of adult hemoglobin A2, has high homology to β-globin and is already pan-cellularly expressed at low levels in adult red blood cells. However, upregulation of δ-globin is a relatively unexplored avenue to increase the amount of functional hemoglobin. Here, we use CRISPR-Cas9 to repair non-functional transcriptional elements in the endogenous promoter region of δ-globin to increase overall expression of adult hemoglobin 2 (HbA2). We find that insertion of a KLF1 site alone is insufficient to upregulate δ-globin. Instead, multiple transcription factor elements are necessary for robust upregulation of δ-globin from the endogenous locus. Promoter edited HUDEP-2 immortalized erythroid progenitor cells exhibit striking increases of HBD transcript, from less than 5% to over 20% of total β-like globins in clonal populations. Edited CD34 +hematopoietic stem and progenitors (HSPCs) differentiated to primary human erythroblasts express up to 46% HBD in clonal populations. These findings add mechanistic insight to globin gene regulation and offer a new therapeutic avenue to treat β-hemoglobinopathies.

Transcriptional Mechanism of the Mouse β4-Galactosyltransferase 6 Gene in Mouse Neuroblastoma Cell Line Neuro-2a

Lactosylceramide (Lac-Cer) constitutes the backbone structure of various gangliosides whose abnormal expression is associated with malignancy of neuroblastoma. The understanding of the regulatory mechanism of Lac-Cer contributes to the development of neuroblastoma therapy. In this study, the transcriptional mechanism of mouse β4-galactosyltransferase (β4GalT) 6, which is one of Lac-Cer synthase, was analyzed using mouse neuroblastoma cell line Neuro-2a. The -226 to -13 region relative to the most downstream transcriptional start site was determined to be the promoter region by luciferase assay using the 5'-deletion constructs. The mutation into the activating protein (AP) 4-binding site -110/-101 drastically decreased the promoter activity, indicating that this site is mainly implicated in the transcription. Furthermore, the mutation into the GATA-binding site -210/-201 or another AP4-binding site -202/-193 partially decreased the promoter activity. The study suggests that the mouse β4GalT6 gene is transcriptionally regulated by AP4 in cooperation with GATA family transcription factor in neuroblastoma.

Fetal Hemoglobin Modulators May Be Associated With Symptomology of Football Players with Sickle Cell Trait

OBJECTIVES

This study investigates whether genetic modifiers previously shown to influence adult fetal hemoglobin (HbF) levels and glucose-6-phosphate dehydrogenase deficiency were associated with variable symptomology in a small sample of collegiate football players with sickle cell trait.

METHODS

Survey data on self-assessed symptoms and genotype data from five single nucleotide polymorphisms (SNPs) related to HbF production and two SNPs that cause glucose-6-phosphate dehydrogenase deficiency were collected from current and former college football players.

RESULTS

In this sample, SNPs found within the β-globin gene cluster were found to be associated with a previous diagnosis of exertional sickling and experience of extreme heat during and after training. rs10189857 in the BCL11A gene was associated with body mass index and weight and with experiencing extreme thirst during and after training. No significant correlations were found between the other SNPs and symptoms within this sample.

CONCLUSIONS

These findings show that genetic variation known to affect sickle cell disease symptomology may partly explain why some football players with sickle cell trait experience adverse clinical outcomes during periods of extreme physical exertion and others do not.

Genetic variation of Krüppel-like factor 1 (KLF1) and fetal hemoglobin (HbF) levels in β0-thalassemia/HbE disease

Heterogeneity of HbF levels in β⁰-thalassemia/HbE disease has been reported to be associated with variations in clinical manifestations of the disease, and several genetic-modifying factors beyond the β-globin gene cluster have been identified as HbF regulators. Down-regulation or heterozygous mutations of Krüppel-like factor 1 (KLF1) is associated with elevated HbF levels in non-thalassemia subjects. This study confirms that experimental down-regulation of KLF1 in β⁰-thalassemia/HbE-derived erythroblasts significantly increases HbF production (up to 52.3 ± 2.4%), albeit with slightly delayed erythroid terminal differentiation. KLF1 exome sequencing of 130 Thai β⁰-thalassemia/HbE patients without co-inheritance of α-thalassemia found six patients with KLF1 heterozygous mutations including rs2072596 (p.F182L; n = 5) and rs745347362 (p.P284L; n = 1) missense mutations. However, while these patients had high HbF levels (38.1 ± 7.5%), they were all associated with a severe clinical phenotype. These results suggest that while reduction of KLF1 expression in β⁰-thalassemia/HbE erythroblasts can increase HbF levels, it is not sufficient to alleviate the clinical phenotype.

Distinctive patterns of evolution of the δ-globin gene (HBD) in primates

In most vertebrates, hemoglobin (Hb) is a heterotetramer composed of two dissimilar globin chains, which change during development according to the patterns of expression of α- and β-globin family members. In placental mammals, the β-globin cluster includes three early-expressed genes, ε(HBE)-γ(HBG)-ψβ(HBBP1), and the late expressed genes, δ (HBD) and β (HBB). While HBB encodes the major adult β-globin chain, HBD is weakly expressed or totally silent. Paradoxically, in human populations HBD shows high levels of conservation typical of genes under strong evolutionary constraints, possibly due to a regulatory role in the fetal-to-adult switch unique of Anthropoid primates. In this study, we have performed a comprehensive phylogenetic and comparative analysis of the two adult β-like globin genes in a set of diverse mammalian taxa, focusing on the evolution and functional divergence of HBD in primates. Our analysis revealed that anthropoids are an exception to a general pattern of concerted evolution in placental mammals, showing a high level of sequence conservation at HBD, less frequent and shorter gene conversion events. Moreover, this lineage is unique in the retention of a functional GATA-1 motif, known to be involved in the control of the developmental expression of the β-like globin genes. We further show that not only the mode but also the rate of evolution of the δ-globin gene in higher primates are strictly associated with the fetal/adult β-cluster developmental switch. To gain further insight into the possible functional constraints that have been shaping the evolutionary history of HBD in primates, we calculated dN/dS (ω) ratios under alternative models of gene evolution. Although our results indicate that HBD might have experienced different selective pressures throughout primate evolution, as shown by different ω values between apes and Old World Monkeys + New World Monkeys (0.06 versus 0.43, respectively), these estimates corroborated a constrained evolution for HBD in Anthropoid lineages, which is unlikely to be related to protein function. Collectively, these findings suggest that sequence change at the δ-globin gene has been under strong selective constraints over 65 Myr of primate evolution, likely due to a regulatory role in ontogenic switches of gene expression.

The genetics of hemoglobin A2 regulation in sickle cell anemia

Hemoglobin A2 , a tetramer of α- and δ-globin chains, comprises less than 3% of total hemoglobin in normal adults. In northern Europeans, single nucleotide polymorphisms (SNPs) in the HBS1L-MYB locus on chromosome 6q and the HBB cluster on chromosome 11p were associated with HbA2 levels. We examined the genetic basis of HbA2 variability in sickle cell anemia using genome-wide association studies. HbA2 levels were associated with SNPs in the HBS1L-MYB interval and SNPs in BCL11A. These effects are mediated by the association of these loci with γ-globin gene expression and fetal hemoglobin (HbF) levels. The association of polymorphisms downstream of the β-globin gene (HBB) cluster on chromosome 11 with HbA2 was not mediated by HbF. In sickle cell anemia, levels of HbA2 appear to be modulated by trans-acting genes that affect HBG expression and perhaps also elements within the β-globin gene cluster. HbA2 is expressed pancellularly and can inhibit HbS polymerization. It remains to be seen if genetic regulators of HbA2 can be exploited for therapeutic purposes.

Repeated evolution of chimeric fusion genes in the β-globin gene family of laurasiatherian mammals

The evolutionary fate of chimeric fusion genes may be strongly influenced by their recombinational mode of origin and the nature of functional divergence between the parental genes. In the β-globin gene family of placental mammals, the two postnatally expressed δ- and β-globin genes (HBD and HBB, respectively) have a propensity for recombinational exchange via gene conversion and unequal crossing-over. In the latter case, there are good reasons to expect differences in retention rates for the reciprocal HBB/HBD and HBD/HBB fusion genes due to thalassemia pathologies associated with the HBD/HBB "Lepore" deletion mutant in humans. Here, we report a comparative genomic analysis of the mammalian β-globin gene cluster, which revealed that chimeric HBB/HBD fusion genes originated independently in four separate lineages of laurasiatherian mammals: Eulipotyphlans (shrews, moles, and hedgehogs), carnivores, microchiropteran bats, and cetaceans. In cases where an independently derived "anti-Lepore" duplication mutant has become fixed, the parental HBD and/or HBB genes have typically been inactivated or deleted, so that the newly created HBB/HBD fusion gene is primarily responsible for synthesizing the β-type subunits of adult and fetal hemoglobin (Hb). Contrary to conventional wisdom that the HBD gene is a vestigial relict that is typically inactivated or expressed at negligible levels, we show that HBD-like genes often encode a substantial fraction (20-100%) of β-chain Hbs in laurasiatherian taxa. Our results indicate that the ascendancy or resuscitation of genes with HBD-like coding sequence requires the secondary acquisition of HBB-like promoter sequence via unequal crossing-over or interparalog gene conversion.

Distinct Ldb1/NLI complexes orchestrate γ-globin repression and reactivation through ETO2 in human adult erythroid cells

The Ldb1/GATA-1/TAL1/LMO2 complex mediates long-range interaction between the β-globin locus control region (LCR) and gene in adult mouse erythroid cells, but whether this complex mediates chromatin interactions at other developmental stages or in human cells is unknown. We investigated NLI (Ldb1 homolog) complex occupancy and chromatin conformation of the β-globin locus in human erythroid cells. In addition to the LCR, we found robust NLI complex occupancy at a site downstream of the (A)γ-globin gene within sequences of BGL3, an intergenic RNA transcript. In cells primarily transcribing β-globin, BGL3 is not transcribed and BGL3 sequences are occupied by NLI core complex members, together with corepressor ETO2 and by γ-globin repressor BCL11A. The LCR and β-globin gene establish proximity in these cells. In contrast, when γ-globin transcription is reactivated in these cells, ETO2 participation in the NLI complex at BGL3 is diminished, as is BCL11A occupancy, and both BGL3 and γ-globin are transcribed. In these cells, proximity between the BGL3/γ-globin region and the LCR is established. We conclude that alternative NLI complexes mediate γ-globin transcription or silencing through long-range LCR interactions involving an intergenic site of noncoding RNA transcription and that ETO2 is critical to this process.

KLF1 gene mutations cause borderline HbA(2)

Increased hemoglobin A(2) (HbA(2); ie, levels > 3.9%) is the most important feature of β-thalassemia carriers. However, it is not uncommon to find persons with borderline HbA(2) (levels, 3.3%-3.8%), who pose a relevant screening problem. Several genotypes have been associated with borderline HbA(2), but sometimes the reasons for this unusual phenotype are unknown. In this paper, we report, for the first time, that mutations of KLF1 result in HbA(2) levels in the borderline range. Six different KLF1 mutations were identified in 52 of 145 subjects with borderline HbA(2) and normal mean corpuscular volume and mean corpuscular hemoglobin. Two mutations (T327S and T280_H283del) are here reported for the first time. The prevalent mutation in Sardinians is S270X, which accounts for 80.8% of the total. The frequent discovery of KLF1 mutations in these atypical carriers may contribute significantly to the thalassemia screening programs aimed at identification of at risk couples.

Recombinant erythroid Kruppel-like factor fused to GATA1 up-regulates delta- and gamma-globin expression in erythroid cells

The β-hemoglobinopathies sickle cell disease and β-thalassemia are among the most common human genetic disorders worldwide. Hemoglobin A2 (HbA2, α₂δ₂) and fetal hemoglobin (HbF, α₂γ₂) both inhibit the polymerization of hemoglobin S, which results in erythrocyte sickling. Expression of erythroid Kruppel-like factor (EKLF) and GATA1 is critical for transitioning hemoglobin from HbF to hemoglobin A (HbA, α₂β₂) and HbA2. The lower levels of δ-globin expression compared with β-globin expression seen in adulthood are likely due to the absence of an EKLF-binding motif in the δ-globin proximal promoter. In an effort to up-regulate δ-globin to increase HbA2 expression, we created a series of EKLF-GATA1 fusion constructs composed of the transactivation domain of EKLF and the DNA-binding domain of GATA1, and then tested their effects on hemoglobin expression. EKLF-GATA1 fusion proteins activated δ-, γ-, and β-globin promoters in K562 cells, and significantly up-regulated δ- and γ-globin RNA transcript and protein expression in K562 and/or CD34(+) cells. The binding of EKLF-GATA1 fusion proteins at the GATA1 consensus site in the δ-globin promoter was confirmed by chromatin immunoprecipitation assay. Our studies demonstrate that EKLF-GATA1 fusion proteins can enhance δ-globin expression through interaction with the δ-globin promoter, and may represent a new genetic therapeutic approach to β-hemoglobinopathies.

Sequence composition similarities with the 7SL RNA are highly predictive of functional genomic features

Transposable elements derived from the 7SL RNA gene, such as Alu elements in primates, have had remarkable success in several mammalian lineages. The results presented here show a broad spectrum of functions for genomic segments that display sequence composition similarities with the 7SL RNA gene. Using thoroughly documented loci, we report that DNaseI-hypersensitive sites can be singled out in large genomic sequences by an assessment of sequence composition similarities with the 7SL RNA gene. We apply a root word frequency approach to illustrate a distinctive relationship between the sequence of the 7SL RNA gene and several classes of functional genomic features that are not presumed to be of transposable origin. Transposable elements that show noticeable similarities with the 7SL sequence include Alu sequences, as expected, but also long terminal repeats and the 5′-untranslated regions of long interspersed repetitive elements. In sequences masked for repeated elements, we find, when using the 7SL RNA gene as query sequence, distinctive similarities with promoters, exons and distal gene regulatory regions. The latter being the most notoriously difficult to detect, this approach may be useful for finding genomic segments that have regulatory functions and that may have escaped detection by existing methods.

delta-Globin gene structure and expression in the K562 cell line

The delta-globin gene produces the delta chain of Hb A2 which represents less than 3% of the hemoglobin (Hb) in normal individuals. The delta-globin gene is also expressed in the human erythroleukemia cell line K562. The expression of the delta-globin gene in this cell line is unexpected since K562 shows an embryonic-fetal globin gene expression pattern with no expression of the adult beta-globin gene. delta-Globin gene activation has been proposed as a potential therapeutic tool for the cure of delta-thalassemia (thal). In order to shed some light on the delta-globin gene activation in K562 the present study has: (1) determined the complete nucleotide sequence of the delta- and beta-globin genes; (2) assessed, by reverse transcription-polymerase chain reaction (RT-PCR), the relative delta- and beta-globin mRNA level; and (3) analyzed the exact level of the endogenous expression delta-globin gene by S1 mapping. No sequence variations were identified in the (delta- and beta-globin genes when compared to the normal sequences. delta-Globin mRNA represent more than 95% of the total delta + beta-mRNA content. The level of expression of the delta-globin gene is 12.3% (+/- 1.2) compared to the endogenous alpha-globin gene. These results indicate that the high expression of the delta-globin gene in K562 is most likely due to the transacting environment. Therefore, the presence and/or absence of specific transacting factors are able to specifically activate the human delta-globin gene. The level of expression of the delta-globin gene in this cell line suggests that it could be of relevance to identify the transacting factor(s) responsible for this selective activation in order to better understand the molecular mechanisms undergoing gene activation.

Human alloantigen-specific anergic cells induced by a combination of CTLA4-Ig and CsA maintain anti-leukemia and anti-viral cytotoxic responses

The success of allogeneic hematopoietic stem cell transplantation from HLA-disparate donors depends on the development of new strategies for graft-versus-host disease prevention able to target specifically donor antihost alloreactivity, while preserving GVL and antiviral immune surveillance. Recent experimental and clinical work has shown the feasibility of an approach based on induction of anergy to host alloantigens through blockade of B7/CD28 costimulatory signal in donor T cells, but data on the impact of this strategy on the recovery of the immune system are still lacking. We devised an ex vivo method for induction of host alloantigen-specific unresponsiveness based on treatment with the B7/CD28 blocking agent CTLA4-Ig associated with CsA. We then proceeded to assess the maintenance of an effective immune response towards viral pathogens and tumor cells after CTLA4-Ig/CsA treatment, by measuring the frequency of CTL precursors directed against CMV- and EBV-infected targets, and against autologous leukemic blasts. We demonstrated that (1) CTLA4-Ig and CsA can act synergistically in inducing a state of unresponsiveness to alloantigens; (2) the number of leukemia-reactive, EBV-specific and CMV-specific CTLp is not impaired by CTLA4-Ig/CsA treatment. Our data provide the first direct in vitro evidence that it is possible to preserve antiviral and antileukemia effector cells after blockade of CD28/B7 interaction during MLR.

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.

Activation of the delta-globin gene by the beta-globin gene CACCC motif

The promoter region of adult beta globin genes in humans and other mammals contains conserved regions of pivotal importance for their regulated tissue specific expression. These include the CACCC and CAAT motifs. The CACCC motif is duplicated in humans and other mammals. The human delta-globin gene lacks these conserved regions and its expression in normal individuals is about 3% that of the beta globin gene. Previous studies have shown that the introduction of the beta-globin CACCC or CAAT can activate the delta-globin gene promoter, but the effect of the distal CACCC element has not yet been tested. In the present study, using site-specific mutagenesis, we have introduced the consensus sequence for the distal and proximal CACCC motif and the CAAT box alone or in combination in the wild-type delta-globin gene promoter. The resulting mutants, as well as the wild type (wt) delta- and beta-globin gene promoters, have been analyzed in a transient expression assay in Cos7, K562, and MEL cell lines. The results show that the CACCC boxes can increase the transcription efficiency of the delta-globin gene promoter in both erythroid and non-erythroid cell systems. The contribution of the two CACCC elements is almost equal in the non-erythroid (Cos7) and erythroid embryonic-fetal cell lines (K562), while the proximal CACCC element is more active in adult erythroid cells (MEL). Nonetheless, duplication of this element does not appear to affect the efficiency of the promoter synergistically. Furthermore, to assess the competitive ability of the delta globin promoter containing the proximal or distal CACCC consensus sequences over the wt beta globin gene promoter, we have carried out transient expression experiments using DNA constructs in which the delta and beta globin gene promoters are linked in cis and are sharing a single enhancer (competitive transient expression). The results show that both CACCC elements are able to activate the delta globin gene promoter in Cos7 and K562 cells, although to a different extent, whereas only the proximal CACCC element is effective in increasing the transcription efficiency in MEL cells. These findings are in agreement with the more severe clinical phenotype produced by the beta-thalassemia mutations affecting the proximal CACCC box as compared with those within the distal CACCC box. The Erythroid Kruppel Like Factor (EKLF) is a nuclear protein restricted to erythroid cells which specifically bind the CACCC box sequence and activate the beta-globin gene. In the present study we carried out transactivation experiments of the mutagenized delta-globin gene promoter by introducing an EKLF expressing construct in erythroid cells. Constructs containing the proximal but not those bearing the distal CACCC element are transactivated. Our results indicate that the proximal CACCC box and, to a lesser extent, also the distal box have a role in the regulated stage specific expression of a beta-like globin gene, and show that the insertion of a single CACCC motif in the delta-globin gene promoter is sufficient to increase its activity. Nevertheless only the delta globin gene promoter containing the proximal CACCC element is able to compete with the wt beta globin gene promoter in the adult erythroid environment. These findings have potential relevance for the future prospective treatment of inherited hemoglobinopathies based on the conversion of the low functioning delta-globin gene into a high functioning beta-like globin gene.

Positive and Negative Cis-Acting Elements Are Required for Hematopoietic Expression of Zebrafish GATA-1

GATA-1 is a transcription factor required for development of erythroid cells. The expression of GATA-1 is tightly restricted to the hematopoietic lineage. Using transgene constructs containing zebrafish GATA-1 genomic sequences and the green fluorescent protein (GFP) reporter gene, we previously showed that a 5.6-kb enhancer/promoter fragment is sufficient to direct erythroid-specific expression of the GFP. In this study, we used enhancer/promoter fragments containing various deletion and point mutations to further characterize the cis-acting elements controlling tissue-specific GATA-1 expression. We report here the identification of distinct cis-acting elements that cooperate to confer on GATA-1 its hematopoietic expression pattern. A CACCC box, located 142 bp upstream of the translation start codon, is critical for the initiation of GATA-1 expression. A distal double GATA element is required for maintaining and enhancing the hematopoietic expression of GATA-1. The erythroid-specific activity of the GATA-1 promoter is also enhanced by a 49-bp sequence element located 218 bp upstream of the CACCC element and a CCAAT box adjacent to the double GATA motif. Finally, the hematopoietic specificity of the GATA-1 promoter is secured by a negative cis-acting element that inhibits expression in the notochord.

Positive and Negative Cis-Acting Elements Are Required for Hematopoietic Expression of Zebrafish GATA-1

GATA-1 is a transcription factor required for development of erythroid cells. The expression of GATA-1 is tightly restricted to the hematopoietic lineage. Using transgene constructs containing zebrafish GATA-1 genomic sequences and the green fluorescent protein (GFP) reporter gene, we previously showed that a 5.6-kb enhancer/promoter fragment is sufficient to direct erythroid-specific expression of the GFP. In this study, we used enhancer/promoter fragments containing various deletion and point mutations to further characterize the cis-acting elements controlling tissue-specific GATA-1 expression. We report here the identification of distinct cis-acting elements that cooperate to confer on GATA-1 its hematopoietic expression pattern. A CACCC box, located 142 bp upstream of the translation start codon, is critical for the initiation of GATA-1 expression. A distal double GATA element is required for maintaining and enhancing the hematopoietic expression of GATA-1. The erythroid-specific activity of the GATA-1 promoter is also enhanced by a 49-bp sequence element located 218 bp upstream of the CACCC element and a CCAAT box adjacent to the double GATA motif. Finally, the hematopoietic specificity of the GATA-1 promoter is secured by a negative cis-acting element that inhibits expression in the notochord.

Binding of HMG-I(Y) elicits structural changes in a silencer of the human beta-globin gene

Proteins involved in repression of the human beta-globin gene may be useful in the treatment of sickle cell anemia, in conjunction with therapy to reactivate fetal globin genes. If there is a reciprocal elevation of gamma-globin expression upon repression, this approach could be useful in additional hemoglobinopathies. We previously showed that repression of the beta-globin gene appears to be mediated through two DNA sequences, silencers I and II, and identified a protein termed BP1 which binds to both silencer sequences. In this study, we cloned two cDNAs encoding proteins which bind to an oligonucleotide in silencer I containing a BP1 binding site. These cDNAs correspond to HMG-I and HMG-Y, isoforms regarded as architectural proteins. We demonstrate that binding of HMG-I(Y) to this oligonucleotide causes bending/flexure of the DNA. HMG-I(Y) also binds to a second oligonucleotide containing a BP1 binding site located in a negative control region upstream of the delta-globin gene, suggesting a role for HMG-I(Y) in repression of adult globin genes. Expression studies revealed that HMG-I(Y) is ubiquitously expressed in human tissues that do not express beta-globin, being present in 48 of 50 tissues and six hematopoietic cell lines examined. Furthermore, HMG-I(Y) expression is down-regulated during differentiation of primary erythroid cells. We present a model in which HMG-I(Y) alters DNA conformation to allow binding of repressor proteins, and in which the relative amount of HMG-I(Y) helps to determine the repressive state of the beta-globin gene.

Activation of the human delta-globin gene promoter in primary adult erythroid cells

Restoration of the CCAAT box or insertion of an erythroid Krüppel-like factor (EKLF) binding site in the delta promoter activates its expression in several erythroid cell lines. We extended these studies using a novel primary human adult erythroid cell (hAEC) system to investigate these effects at the late erythroblast stage. Restoration of the CCAAT box at -70 bp, or insertion of an EKLF binding site at -85 bp or -95 bp in the promoter significantly increased delta globin gene expression in hAEC. Our results demonstrate that the altered CCAAT box (CCAAC) and the lack of an EKLF binding site in delta-globin contribute to its low level of expression in the hAEC model as well.

Manipulating the Immunologic Characteristics of Both Graft and Host to Improve Transplant Outcome

BACKGROUND: Several critical outcomes of allogeneic stem cell transplantation for hematologic malignancies such as engraftment, incidence of graft-vs-host disease (GVHD) and disease-free survival depend on a balance between residual host and infused donor T cells and on chemosensitivity of the underlying disorder. Manipulating cell compartments of the allograft does affect long-term outcome. METHODS: The authors review investigations on the effect of blood and marrow graft components, treatment regimens, and immunologic interventions on eventual transplant outcome, an approach termed "graft engineering." Results: Major advances in graft engineering over the last decade are presented as a series of related developments or levels that derive from the goals of reducing GVHD and minimal residual disease. CONCLUSIONS: Morbidity and mortality of GVHD have decreased markedly by methods of T-cell depletion but at the expense of recurrent disease. Cellular therapy and immunotherapy show promise in potentially eradicating residual disease posttransplant.