Detection of a frequent restriction fragment length polymorphism in the human T cell antigen receptor beta chain locus. A potential diagnostic tool.

Abnormal T cell function is a feature of a spectrum of inherited and acquired diseases. We have detected a frequent restriction fragment length polymorphism in the human T cell antigen receptor beta-chain locus that may aid in the analysis of these disorders. A study of a panel of 18 normal individuals, testing for the presence of the polymorphism, showed it to account for 36% of the alleles in that group. In view of the fact that the T cell receptor beta-chain locus has been mapped to chromosome 7, and that the disease ataxia telangiectasia (AT) is associated both with abnormal T cell function and with chromosomal abnormalities of the same region of chromosome 7, we investigated the possibility that the polymorphism could demonstrate linkage of the T cell receptor locus to the gene for that disease. We demonstrated that the mutation causing AT did not lie within the beta-chain locus itself, and that there was preliminary evidence that the two loci were not closely linked. This polymorphism may provide a useful tool for the study of other genetic disorders associated with abnormalities of T cell function, as well as disorders associated with inherited or acquired abnormalities of chromosome 7.

Expression of multiple Na+,K+-adenosine triphosphatase isoform genes in human hematopoietic cells. Behavior of the novel A3 isoform during induced maturation of HL60 cells.

Multiple isoenzymes of the Na+,K+-ATPase (alpha, alpha+, and alpha 3) have been identified by molecular cloning (Shull, G. E., J. Greeb, and J. B. Lingrel. 1986. Biochemistry. 25:8125-8132; and Schneider, J. W., R. W. Mercer, and E. J. Benz, Jr. 1987. Clin. Res. 35:585A. [Abstr.]). At least one of these, the alpha 3 chain, represents a novel form for which protein products and enzymatic activities are just beginning to be defined in rodents. We have recently demonstrated that expression of alpha 3 is largely confined to neuromuscular tissues of fetal and adult rats (Schneider, J. W., R. W. Mercer, M. Gilmore-Hebert, M. F. Utset, C. Lai, A. Greene, and E. J. Benz, Jr. 1988. Proc. Natl. Acad. Sci. USA. 85:284-288). We now report that certain human leukemia cell lines including HL60, HEL, and Molt 4 express mRNA for both alpha and alpha 3 isoforms of Na+,K+-ATPase; mRNA was not detected in several other cell lines, including K562 and U937; no cell lines expressed alpha+ mRNA. In uninduced HL60 cells, alpha 3 mRNA comprised 20-30% of total Na+,K+-ATPase mRNA. Furthermore, in HL60 and HEL cells, both alpha and alpha 3 mRNA declined after induction of maturation by DMSO, retinoic acid, or hemin. However, the reduction in alpha 3 mRNA was far more dramatic. alpha 3 mRNA virtually disappeared, but alpha mRNA declined by only approximately 50%. In contrast, when maturation of HL60 cells along the monocyte/macrophage lineage was induced by exposure to phorbol esters, alpha 3 mRNA remained abundant. Moreover, mRNA for the beta subunit of the Na+,K+-ATPase increased dramatically. Our results demonstrate that the alpha 3 isoform, formerly thought to be confined to neuromuscular tissues, is expressed in restricted lineages of hematopoietic origin. These leukemia cell lines should provide a useful model for analyzing regulation of the alpha 3 isoform gene and characterization of alpha 3 isoform activities.

Retroviral insertional activation of the EVI1 oncogene does not prevent G-CSF-induced maturation of the murine pluripotent myeloid cell line 32Dcl3.

Evi1 is a myeloid-specific protooncogene that encodes 145 kDa and 88 kDa proteins via alternative splicing. Overexpression of the gene via retroviral insertion in murine tumors or chromosomal rearrangement in human tumors is associated with myeloid leukemias and myelodysplasias; however, the mechanism by which such overexpression leads to transformation is not clear. It has been postulated that overexpression of evi1 acts to block normal myelopoiesis. In attempts to assess the effect of overexpression of evi1 on myelopoiesis, we chose to utilize the IL-3-dependent murine 32Dcl3 cell line, which has been shown to differentiate in culture in response to G-CSF. Previous experiments with this cell line, which we have confirmed, showed that overexpression of evi1, mediated by retroviral vector transfer, caused a block to G-CSF-induced cell survival and differentiation. We report here that the naive 32Dcl3 cell line contains a rearrangement of the evi1 locus and constitutively overexpresses evi1 mRNA and protein; this expression is downregulated only slightly during G-CSF-induced myeloid maturation. The steady state levels, molecular weight and DNA binding characteristics of the EVI1 protein in these cells is comparable to that seen in NFS 58, a myeloid leukemia cell line with retroviral insertion at evi1. The observed ability of the murine 32Dcl3 cells to fully differentiate in the presence of G-CSF while evi1 continues to be expressed indicates that, at the levels expressed in naive 32Dcl3, evi1 does not block G-CSF-induced survival and differentiation. Thus, retroviral insertions at evi1 may have been selected for in 32Dcl3 cells due to effects other than that on G-CSF-induced cell survival.

Neutrophil maturation and the role of retinoic acid.

Neutrophil maturation occurs in well defined morphological stages that correlate with the acquisition of molecular markers associated with neutrophil function. A variety of factors are known to play a role in terminal neutrophil maturation, including the vitamin A derivative, retinoic acid. Retinoic acid can directly modulate gene expression via binding to its nuclear receptors, which can, in turn, activate transcription of target genes. A role for retinoic acid during neutrophil maturation has been suggested from a variety of sources. Here we present a review of the mechanism of retinoic acid receptor action and the major evidence showing that normal retinoid signaling is required for neutrophil maturation.

Normal neutrophil differentiation and secondary granule gene expression in the EML and MPRO cell lines.

The EML and MPRO cell lines express a dominant negative retinoic acid receptor alpha that causes a block at specific stages of myelopoiesis. The EML cell line is multipotent and gives rise to erythroid, lymphoid, and myeloid lineages depending on the presence of appropriate cytokines. The MPRO cell line is promyelocytic and undergoes neutrophilic differentiation when induced with all-trans retinoic acid in the presence of granulocyte/macrophage colony-stimulating factor. Previous studies have shown that both of these cell lines undergo morphological differentiation into neutrophils. In this study, we show that unlike other models of neutrophil differentiation such as NB4 and HL60, both EML and MPRO cell lines undergo complete, normal granulocytic differentiation programs. Similar to HL60, MPRO and EML induce expression of CD11b/CD18 and also exhibit downregulation of CD34 on differentiation. In contrast to HL60 and NB4, EML and MPRO cell lines coordinately upregulate secondary granule transcripts for lactoferrin and neutrophil gelatinase. Furthermore, we have confirmed previous observations that serum can induce a low level of differentiation in MPRO cells and that it is possible to grow these cells in serum-free medium, thereby eliminating this effect. Based on these studies, it appears that these lines can serve as a model for normal retinoic acid-induced neutrophil differentiation and provide insight into the role of the retinoic acid-responsive pathway in normal and leukemic myelopoiesis.

Modulation of a calcium/calmodulin-dependent protein kinase cascade by retinoic acid during neutrophil maturation.

Retinoic acid is a lipophilic derivative of vitamin A that can cause differentiation in a variety of cell types. A large body of evidence has shown that normal retinoid signaling is required for proper neutrophil maturation in vitro and in vivo. In this study, we have found that calcium/calmodulin dependent (CaM) protein kinase kinase alpha (CaMKKalpha) is upregulated in an immediate early fashion during retinoic acid induced neutrophil maturation. Furthermore, we describe the expression and modulation of various components of the CaM kinase cascade during neutrophil maturation. We have confirmed upregulation of CaMKKalpha protein by Western analysis and further show that CaMKKbeta is expressed, although its protein levels are constant throughout induction. We also find that neutrophil progenitor cells express both CaMKI and CaMKIV transcripts. RNase protection and Western analysis show that CaMKIV is downregulated during neutrophil maturation. In contrast, CaMKI transcript and protein is expressed in uninduced cells and is induced by all-trans retinoic acid. These data represent the first report of a CaM kinase cascade in myeloid cells and suggests that this cascade may mediate some of the well-characterized effects of calcium on neutrophil function. These observations also support the idea that the retinoic acid receptors play a major role in mediating neutrophil specific gene expression and differentiation.

Introduction: molecular diagnostics in hematology.

Advances in molecular biology of the last 30 tears have transformed the field of hematology. Molecular analysis has clarified the pathogenesis of a host of hematologic disorders, including hemoglobinopathies, coagulation disorders, hypercoaguable states, and hematologic malignancies. This volume is aimed at bringing these compelling advances in molecular biology research to the bedside. Through progress in the molecular understanding of hematology, great strides have been made in our ability to diagnose and treat patients with hematologic disease. These advances in turn have given rise to more questions that will guide future studies of the biology of hematopoietic abnormalities and continue the exciting interaction of basic science and clinical medicine.

Control of late neutrophil-specific gene expression: insights into regulation of myeloid differentiation.

During myeloid differentiation, the pluripotent hematopoietic stem cell passes through several well-defined morphologic stages within the bone marrow. These changes include progressive nuclear segmentation and the acquisition of stage-specific granules. Primary granules appear at the myeloblast stage, and are found in both neutrophils and monocytes. At the myelocyte stage, neutrophil precursors acquire specific granules, a marker of commitment to terminal neutrophil differentiation. This complex developmental pathway is just beginning to be elucidated. Current evidence suggests that myeloid differentiation is regulated primarily by transcriptional regulatory proteins, and that dysfunction of those regulators is involved in most disorders of neutrophil maturation. Furthermore, there is evidence that study of late gene expression may provide insights into more proximal events in granulocytic maturation. In this review, we provide a brief overview of myeloid differentiation with emphasis on the culture systems available for the study of granulopoiesis and the insights they provide into the regulation of late neutrophil-specific gene expression. We discuss the relevance of these observations to our understanding of the pathogenesis of defects in neutrophil differentiation.

Uptake and metabolism of free cyanocobalamin by cultured human fibroblasts from controls and a patient with transcobalamin II deficiency.

We have investigated the uptake and metabolism of free cyanocobalamin (CN-Cbl; vitamin B12) by intact cultured human skin fibroblasts. Monolayers of control fibroblasts take up free CN-[57Co]Cbl via a saturable, calcium-independent process that is inhibited by sulfhydryl reagents, inhibitors of protein synthesis, and inhibitors of electron transport, but not by inhibitors of glycolysis. CN-Cbl taken up in this manner is converted to active cobalamin (Cbl) coenzymes (adenosylcobalamin and methylcobalamin) and becomes associated with intracellular Cbl-dependent apoenzymes (methylmalonyl CoA mutase and homocysteine:methyltetrahydrofolate methyltransferase). Since fibroblasts from controls were also found to synthesize transcobalamin II (TC II), a plasma protein shown previously to facilitate the cellular uptake of Cbl, it seemed possible that the observed uptake of free CN-Cbl was TC II-mediated. This thesis was rejected by demonstrating that cells from a patient with complete TC II deficiency took up free CN-Cbl as well as control cells did. Finally, we propose a mechanism by which an uptake process for free Cbl might serve a function in intracellular metabolism of Cbl.

T gamma lymphocytosis and T cell chronic leukemias.

The T cell chronic leukemias encompass a broad spectrum of diseases involving mature post-thymic T cells. With the development of highly specific marker studies, clear patterns of immunophenotypic and functional characteristics of the involved cells have emerged. These studies, along with the development of molecular probes for the T cell receptor gene loci, have helped to elucidate the pathogenetic basis for the highly variable clinical course which has been described for patients with these disorders. The T gamma lymphocytosis syndrome has been identified as a benign chronic illness which is nevertheless usually a monoclonal neoplastic proliferation of large granular lymphocytes. These patients represent a distinct clinical entity characterized by splenomegaly, neutropenia, and peripheral blood lymphocytosis. The cells of TGLS are large granular lymphocytes and display many of the immunophenotypic and functional characteristics of NK and K cells. These cells have been implicated pathogenetically in the associated cytopenias seen in the illness, but a clear link has not been established. Although the lymphoproliferative manifestations of the disease are usually easily controlled with low-dose alkylating agents, therapy of the neutropenia has been relatively unsuccessful. Separating these patients from the rest of the spectrum of the T cell chronic leukemias has provided insight into the other disorders as well. It has established that T-CLL and T-PLL are, in fact, extremely rare. T-CLL is similar to its B cell counterpart, except that patients have a higher incidence of skin infiltration. Available data suggest that the prognosis in T-CLL is actually less variable, and somewhat worse, than generally believed when those patients were viewed in conjunction with the patients with the more benign TGLS. T-PLL is an extremely aggressive disease characterized by massive splenomegaly, lymphadenopathy, and skin infiltration. It is refractory to most forms of therapy. These illnesses are again phenotypically distinct from the retrovirus-associated ATLL. Most of the early cases of T-CLL reported from Japan were probably ATLL; this disease is characterized by pronounced splenomegaly, hepatomegaly, lymphadenopathy, and skin infiltration. It has an extremely aggressive natural history, and survival is usually less than 1 year from diagnosis. The rapid development of sophisticated immunologic and molecular techniques for analyzing T cell proliferations has allowed highly specific distinctions to be made among the cells of origin of the different T cell chronic leukemias. It is hoped that increased understanding of the immunologic and functional characteristics of these diverse T lymphoid populations will provide further insights which will have an impact on directed therapeutic interventions in the future.

Retinoids in myelopoiesis.

The vitamin A derivative retinoic acid plays a critical role during the differentiation of myeloid progenitors towards the neutrophil lineage. This role is primarily mediated by binding of retinoic acid to retinoic acid receptor alpha (RARalpha), a nuclear receptor that modulates the expression of multiple downstream targets via retinoic acid response elements. The importance of this signalling pathway in myelopoiesis is evidenced by the recurrent disruption of the RARalpha gene by chromosomal rearrangements in all cases of acute promyelocytic leukemia (APL). Biochemical evidence suggests RARalpha performs two opposing functions, one as a repressor of gene expression in the absence of ligand, the second as a transcriptional activator in the presence of ligand, each controlled by multimeric complexes of transcription corepressors and coactivators, respectively. Here the molecular mechanisms activated by retinoic acid during myelopoiesis in the context of neutrophil development will be reviewed, together with some of the more recently identified targets of the retinoic signalling pathway.

Molecular biology of neutrophil differentiation.

Myeloid precursors undergo striking morphologic and functional changes during the process of granulocytic maturation. These changes are associated with significant changes in cell size and nuclear shape, and with the development of stage-specific organelles which contain proteins necessary for the highly specialized roles of neutrophils in phagocytosis, in bacterial killing, and in mediating the inflammatory response. This complex process reflects a carefully regulated and sequential pattern of gene expression, which only recently has begun to be understood at the molecular level. The critical signals for the neutrophil differentiation program are postulated to derive from cytokines, and these cytokines are thought to induce a series of maturational events primarily by transcriptional regulation of sequentially expressed genes. Recent studies have identified a large number of transcriptional regulators, both positive and negative, that appear to act in concert in the developing neutrophil. These genes drive the complex and delicately timed sequence of genetic events that takes the cell from a progenitor to a functionally active neutrophil. Many of these genes are expressed throughout neutrophil differentiation, however, and the ongoing challenge is to elucidate how the function of these factors is modulated to allow the induction of sequential gene expression.

Cloning and expression of the cDNA encoding mouse neutrophil gelatinase: demonstration of coordinate secondary granule protein gene expression during terminal neutrophil maturation.

The 92-kD form of human type IV collagenase (gelatinase) is a member of the matrix metalloproteinase family. It is restricted in its expression to the granulocytic lineage of white blood cells. Within neutrophils it resides in secondary granules, which are markers of terminal myeloid differentiation. We have isolated and sequenced the cDNA encoding the murine counterpart to the human 92-kD metalloproteinase from a macrophage cDNA library. The human and murine genes are highly homologous and exist in an identical form in neutrophils and monocyte-macrophages in both species. Two polyadenylation signals are present in the murine 3' untranslated sequence, accounting for equal expression of two messenger RNAs. We have shown that expression of gelatinase mRNA is controlled in a coordinate fashion together with lactoferrin, also a component of neutrophil secondary granules, and that this control occurs at the level of transcription. This is the first definitive demonstration of coordinate transcriptional regulation of secondary granule protein gene expression, a feature of normal myelopoiesis that is deranged in leukemogenesis.

Representational difference analysis of a committed myeloid progenitor cell line reveals evidence for bilineage potential.

In this study we have sought to characterize a committed myeloid progenitor cell line in an attempt to isolate general factors that may promote differentiation. We used cDNA representational difference analysis (RDA), which allows analysis of differential gene expression, to compare EML and EPRO cells. We have isolated nine differentially expressed cDNA fragments as confirmed by slot blot, Northern, and PCR analysis. Three of nine sequences appear to be novel whereas the identity of the remaining fragments suggested that the EPRO cell line is multipotent. Among the isolated sequences were eosinophilic, monocytic, and neutrophilic specific genes. Therefore, we tested the ability of EPRO cells to differentiate along multiple myeloid lineages and found that EPRO cells exhibited morphologic maturation into either monocyte/macrophages or neutrophils, but not eosinophils. Furthermore, when EPRO cells were exposed to ATRA, neutrophil specific genes were induced, whereas monocytic markers were induced by phorbol ester treatment. This study highlights the use of cDNA RDA in conjunction with the EML/EPRO cell line to isolate markers associated with macrophage and neutrophil differentiation and establishes the usefulness of this system in the search for factors involved in myeloid commitment.

Structure and expression of the cDNA encoding human neutrophil collagenase.

We have isolated and characterized a 2.4-kb cDNA clone encoding human neutrophil collagenase (HNC), a member of the family of matrix metalloproteinases restricted to secondary granules within neutrophils. Partial amino acid sequence was used to deduce oligonucleotide probes. These probes were used to screen a human granulocyte cDNA library derived from messenger RNA (mRNA) from a patient with chronic granulocytic leukemia. Cell-free translation of RNA produced from the cDNA produced a 52-Kd protein that was recognized by anti-HNC antibody. The cDNA clone was sequenced and shown to encode a 467-residue protein whose sequence matched those regions currently known for HNC. The enzyme exhibits 58% homology to human fibroblast collagenase and has the same domain structure. It consists of a 20-residue signal peptide, and an 80-residue propeptide that is lost on autolytic activation by cleavage of an M-L bond. Other regions identified include the autolytic degradation site, the "cysteine switch" residue that is involved in latency and activation, and a putative zinc binding sequence. HNC has six potential N-linked glycosylation sites. The cDNA hybridized to a 3.4-kb mRNA in RNA from a patient with chronic granulocytic leukemia, but not to RNA from uninduced HL60 cells or HL60 cells that had been induced to undergo granulocytic or monocytic maturation with dimethyl sulfoxide or 12-O-tetradecanoylphorbol 13-acetate, respectively. These results parallel those seen with lactoferrin and transcobalamin I, two other secondary granule proteins.

Correlation of messenger RNA levels with protein defects in specific granule deficiency.

Neutrophil specific granule deficiency (SGD) is a rare congenital disorder of unknown cause associated with an impaired inflammatory response and an absence of neutrophil secondary granules. Reduced levels of several neutrophil proteins have led to the suggestion that the defect may lie at the level of transcription, a hypothesis that is supported by abnormally low levels of lactoferrin message in the bone marrow of two SGD patients. We have examined the level of seven granule protein RNAs in one SGD patient and have compared them with reported protein levels. We have found the RNA levels for all of these genes to be reduced in proportion to the decreased levels of their respective proteins. These data further support the hypothesis that the reduced protein levels reflect a defect in transcriptional control.

Isolation and characterization of the cDNA for mouse neutrophil collagenase: demonstration of shared negative regulatory pathways for neutrophil secondary granule protein gene expression.

A characteristic of normal neutrophil maturation is the induction of secondary granule protein (SGP) mRNA expression. Several leukemic human cell lines mimic normal morphologic neutrophil differentiation but fail to express SGPs, such as lactoferrin (LF) and neutrophil gelatinase (NG). In contrast, two murine cell lines (32D C13 and MPRO) are able to differentiate into neutrophils and induce expression of LF and NG. Therefore, to study the normal regulation and function of these genes, the corresponding murine homologs must be isolated. Using cDNA representational difference analysis (RDA) to compare a committed myeloid progenitor cell line (EPRO) with the multipotent stem cell line from which it was derived (EML), we isolated a fragment bearing homology to human neutrophil collagenase (hNC). Here, we describe the cloning and characterization of a full-length ( approximately 2 kb) clone that exhibits nearly 65% nucleotide and 73% amino acid identity to hNC. Ribonuclease protection analysis (RPA) of the tissues and cell lines shows that mouse NC (mNC) is expressed only in cell lines exhibiting neutrophilic characteristics, further confirming its identity as the mouse homolog of hNC. Furthermore, we have demonstrated a shared negative regulatory pathway for this and other SGP genes. We have previously shown that CCAAT displacement protein (CDP/cut) binds to a specific region of the LF promoter, and overexpression of CDP blocks G-CSF-induced upregulation of LF gene expression in 32D C13 cells. We show here that in these cells, upregulation of both NC and NG is also blocked. CDP is thus the first identified transcription factor that is a candidate for mediating the shared regulation of neutrophil SGP protein genes.

Structure of the cDNA encoding transcobalamin I, a neutrophil granule protein.

Transcobalamin I (TCI) is a member of the R binder family of vitamin B12 binding proteins. It is a major protein constituent of secondary granules in neutrophils. We have isolated and characterized full length cDNA clones encoding TCI in order to determine whether its expression is coordinately regulated with the appearance of secondary granules and whether it is consequently a useful marker of granulocyte development. Partial amino acid sequences of human R protein were obtained from tryptic digestion fragments. Using the polymerase chain reaction, a partial TCI cDNA probe was isolated by selective amplification of a region of cDNA located between two oligonucleotides deduced from the available partial amino acid sequences. The amplified probe was then used to obtain full length clones from a granulocyte cDNA library. Identity of the clones was confirmed by matching DNA sequence to known peptide amino acid sequence. TCI is transcribed to a single 1.5-kilobase mRNA species. The predicted protein sequence is 433 amino acids long. We have compared the sequence of TCI to that of rat intrinsic factor. The two proteins have areas of extensive homology which implicate regions potentially important for vitamin B12 binding. TCI mRNA was present in late neutrophil precursors but absent from uninduced and induced HL60 cells.