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S Surrey

Publications and source records attributed to S Surrey.

At least 91 records · Page 5Linked to original sources
PubMed1990

Biologic and biochemic properties of recombinant platelet factor 4 demonstrate identity with the native protein.

Platelet factor 4 (PF4) is a 70 amino acid protein released from the alpha-granules of platelets after activation. The exact biologic function of this protein is unknown. We have constructed an expression vector for recombinant PF4 (rPF4) in the T7-based promoter vector pT7-7 to better study the relationship between PF4 structure and function. The protein was expressed in Escherichia coli and purified to homogeneity by heparin-agarose affinity chromatography and reverse-phase high-performance liquid chromatography. Purity of protein was confirmed by immunoblot analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which resulted in a single component with a molecular weight of 8,000 daltons. The amino acid composition and sequence of the N-terminal 20 residues showed that rPF4 is identical to PF4 prepared from human platelets (hPF4), except for an N-terminal initiating methionine residue. Immunoblots revealed that rPF4 and hPF4 bound polyclonal anti-hPF4 equally well, while chemotaxis experiments demonstrated similar potencies as neutrophil attractants. Dose-dependent neutrophil chemotactic responses and competitive studies with polyclonal anti-hPF4 antiserum further demonstrate similar chemotactic properties of the two PF4 species. In conclusion, our data show that this recombinant protein and the native protein appears to have similar immunologic, heparin-binding, and chemotactic properties. The chemotactic properties of hPF4 appear to be entirely intrinsic to the protein and not due, in part, to any contaminating protein. Furthermore, our expression vector should prove useful for the construction of recombinant forms of PF4 to investigate structure/function relationships of this biologically important protein.

Amino Acid Sequence↗
PubMed1990

Organization of the gene for platelet glycoprotein IIb.

The glycoprotein (GP) IIb/IIIa heterodimer functions as a receptor for fibrinogen, von Willebrand factor, and fibronectin on activated platelets; it is dysfunctional in the bleeding diathesis Glanzmann's thrombasthenia. This receptor is a member of the integrin family, which includes homologous membrane receptors involved in a number of different cell-cell and cell-matrix adhesive interactions. Knowledge of the sequence and organization of the GPIIb and GPIIIa genes will help in understanding evolutionary relationships and functional homologies of this family of adhesion protein receptors and will facilitate analysis of molecular defects responsible for thrombasthenia. Using the GPIIb cDNA as a probe, we have isolated overlapping genomic clones encompassing the entire coding region, the 5'- and 3'-untranslated sequences, and the immediate flanking regions for the GPIIb gene. The gene spans approximately 17.2 kilobases (kb); all but approximately 2.6 kb of intronic DNA sequence has been determined. The GPIIb gene contains 30 exons whose demarcations do not correlate with previously suggested functional domains. Two intron/exon borders have the rare GC splice donor sequence instead of the consensus GT sequence. There are at least seven complete and three partial AluI sequence repeats within the intron sequences. RNase protection, S1 nuclease analysis, and primer extension studies using human erythroleukemia (HEL) cell RNA and platelet RNA map a major transcription start site 32 base pairs (bp) 5' to the beginning of the coding region; however, there are no canonical consensus TATA or CAAT boxes in the region immediately 5' to the proposed cap site. The immediate 5'-flanking sequence of rodent GPIIb demonstrates complete identity near the proposed cap site with its human counterpart, but again, no TATA or CAAT boxes are apparent.

Amino Acid Sequence↗
PubMed1990

The -175T----C mutation increases promoter strength in erythroid cells: correlation with evolutionary conservation of binding sites for two trans-acting factors.

A point mutation at position -175 has been detected in Agamma as well as Ggamma globin genes in individuals with hereditary persistence of fetal hemoglobin (HPFH). To prove that this single point mutation results in increased promoter strength, we transfected erythroid and nonerythroid cell lines with constructs containing normal and mutant promoters linked to the bacterial chloramphenicol acetyl transferase (CAT) gene. Differences in transfection efficiency were controlled by cotransfection of pRSVgpt. In K562 erythroleukemia cells, the -175 HPFH promoter directed three- to fourfold more CAT activity than its wild type counterpart. However, in HeLa cells the two promoters were similar in strength. The -195 to -165 region of the gamma-globin promoter contains binding sites for two proteins: a ubiquitously distributed octamer binding protein, OBP, and the erythroid-specific protein, GF-1. We find that while the GF-1 binding site is highly conserved among related primate gamma-globin genes, the octamer binding site is not. The evolutionary conservation of GF-1 as well as its erythroid-specific distribution suggest that this protein is important in gamma-globin gene expression. A role for OBP in the regulation of gamma-globin, if any, must have arisen recently in primate evolution.

Animals↗
PubMed1990

Analysis of 5' flanking regions of the gamma globin genes from major African haplotype backgrounds associated with sickle cell disease.

There are at least three major African haplotype backgrounds on which the beta s mutation arises. Sequence changes in the immediate 5' flanking area of the gamma-globin genes may account for differences in fetal hemoglobin expression among the three haplotypes. We determined the sequence from -350 to 10 bp 5' of the G gamma and A gamma fetal globin genes from one beta s-containing chromosome on each of the three major haplotype backgrounds. The Senegal chromosome had a T at -158 5' to the G gamma gene; the Benin (BEN) chromosome had an A to G change at -309 5' to the G gamma gene; and the Central African Republic (CAR) chromosome had a C to T change at -271 5' to the A gamma gene. Genomic DNA from patients with sickle cell disease was analyzed using the polymerase chain reaction and radiolabeled allele-specific oligonucleotide probes. The -309 G variant 5' to the G gamma gene is associated with BEN chromosomes, and the -271 T variant 5' to A gamma with CAR. The -309 change was also found on beta A-containing chromosomes, while the -271 change was not. The -309 change may have predated the beta s mutation on the BEN chromosome.

Anemia, Sickle Cell↗
PubMed1990

Beta-globin gene cluster haplotypes in Hb C heterozygotes.

Previous work has suggested that the beta C mutation arose on a relatively rare beta A chromosome with a unique haplotype, and these data have been used to postulate a single origin of the beta C allele. Most characteristic of this haplotype has been the absence of a Hpa I recognition site 3' to the beta-globin gene. We studied 40 patients with Hb SC, 11 with Hb AC, and one with Hb CC. Complete haplotyping was possible on 44 beta C alleles and 3' haplotyping was possible on an additional four beta C alleles. Our results support the predominence of a unique beta C haplotype which is characterized by the absence of the Hpa I site. However, one patient who was homozygous for Hb C had one beta C allele with an atypical haplotype which contained the Hpa I site. It is unclear at this time whether or not this represents a second origin of the beta C mutation.

Anemia, Sickle Cell↗
PubMed1990

Retroviral transfer of genes into erythroid progenitors derived from human peripheral blood.

Human erythroblasts are a logical target for studies of expression of transferred globin genes because high-level expression is a prerequisite for gene therapy of hemoglobinopathies. Early erythroid progenitors (erythroid burst-forming units, BFU-E) are readily available from human peripheral blood and can be cultured to produce erythroblasts. However, conditions for efficient transfer into these normal progenitors have not been previously described. Here we demonstrate efficient transfer of the neomycin resistance gene into human peripheral blood BFU-E using the retrovirus vector, N2. We show that liquid culture of mononuclear cells from peripheral blood for 18-24 h prior to retroviral infection leads to increased transfer efficiency of N2 as determined by G418 resistance, and we are able to detect viral DNA by polymerase chain reaction (PCR) analysis. In addition, a second retrovirus, beta(gamma)-SVX, prepared with a human beta-globin gene containing a gamma-globin second exon to facilitate transcript detection and the 3'-enhancer sequence, was also used to determine whether similar results could be obtained when more than one gene is transferred. Using the beta(gamma)-SVX virus, increased transfer efficiency into BFU-E was similarly found after liquid culture for up to 4 days. Expression of the transferred globin gene was also detected by PCR analysis of cDNA made from erythroblast RNA. The human peripheral blood BFU-E system described should allow determination of sequences required for high-level expression of transferred globin and other erythroid genes.

Base Sequence↗
PubMed1988

A large deletion encompassing the entire alpha-like globin gene cluster in a family of northern European extraction.

We describe a new deletional form of alpha thalassemia segregating in three generations of a family of northern European origin. A full-term female girl had hypochromic, microcytic anemia since early infancy associated with delayed language development, slow growth and weight gain. Hematologic studies suggested the presence of alpha thalassemia. Gene-blotting studies showed no abnormal alpha-like globin gene fragments; however, studies of inheritance of informative polymorphic restriction fragments using zeta, alpha and 3'-alpha-hypervariable region (3'-HVR) probes showed evidence for an extensive deletion encompassing the entire alpha-like globin gene cluster. The 3' breakpoint of this deletion maps beyond the 3'-HVR, a region implicated as a hot spot for the generation of other large deletional events within the alpha-like cluster. The 5' breakpoint maps at least 10 kilobases (kb) 5' to the zeta-globin gene. The minimum size estimate for this deletion is greater than 47 kilobases.

Child, Preschool↗
PubMed1988

Facilitation of Hb S polymerization by the substitution of Glu for Gln at beta 121.

In an effort to clarify the role of Glu-beta 121 of Hb S molecules in polymerization, we studied the solubility and kinetics of polymerization of various mixtures of deoxyhemoglobins S (Glu-beta 6----Val) and D Los Angeles (Glu-beta 121----Gln). It is known that patients with Hb S-D Los Angeles have a relatively severe clinical course. Mixtures of Hb S and Hb D Los Angeles polymerized after a distinct delay time, the length of which depended on the initial hemoglobin concentration and the fraction of Hb S in the mixture. There was a linear relationship between the logarithmic plot of delay time and initial hemoglobin concentration. The line for a 1:1 mixture of Hb S and Hb D Los Angeles shifted to the right of that for deoxy-Hb S by 0.08. This shift is much smaller than the shift of 0.32 for 1:1 AS mixtures. From these data, the probability factor for nucleation of S-D Los Angeles hybrid hemoglobin was calculated to be 1.16, which is higher than that of Hb S (1.0) and AS hybrid hemoglobin (0.5). The degree of co-polymerization of Hb D Los Angeles in S-D Los Angeles mixtures was similar to that of Hb A in AS mixtures. The critical concentration for the polymerization of Hb D Los Angeles was between that of Hb A and Hb Machida, which has the same amino acid substitution (Glu----Gln) at the beta 6 position. These results suggest that the protein interaction of Hb S molecules during nucleation involves at least two steps. First, the Val-beta 6 of a Hb S molecule interacts hydrophobically with the Phe-beta 85 and the Leu-beta 88 of an adjacent Hb S molecule. In the second step, Glu-beta 121 weakens the interaction with His-beta 116 and Pro-alpha 114. The substitution of Glu-beta 121----Gln may strengthen this second reaction and facilitate nucleation as well as polymerization.

Glutamates↗
PubMed1988

Protection of uninfected human bone marrow cells in long-term culture from G418 toxicity after retroviral-mediated transfer of the NEOr gene.

The long-term effect of retroviral-mediated gene transfer into human hematopoietic cells in vitro was studied in bone marrow culture. Two retroviral vectors (pN2 or pZIP NEO) were used to transfer the gene coding for neomycin phosphotransferase, which confers neomycin resistance, as a dominant selectable marker. Following infection, bone marrow cells of multiple hematopoietic lineages displayed resistance for the duration of the cultures (greater than 80 days) to normally cytotoxic doses of the neomycin analog G418. However, upon DNA analysis of cells surviving in G418, the NEOr (neomycin resistance) gene was not detected under conditions where single copy genes could readily be seen, despite the presence of NEOr RNA sequences. In order to investigate this observation further, infected and uninfected cells were separated by a filter, and cultured in the same medium containing G418. The uninfected cells continued to survive in the presence of normally toxic concentrations of G418. Medium alone from infected cells was able to protect uninfected cells the same way. Efficiency of transfer of this and perhaps other selectable marker genes to cells in the long-term culture system may consequently be overestimated if survival of cells alone is quantitated. These results indicate that long-term cultures are a useful in vitro model for the study of retroviral-mediated gene transfer to human hematopoietic cells.

Cells, Cultured↗
PubMed1988

Overview of the beta thalassemias: genetic and clinical aspects.

There has been much progress in basic studies of the beta-thalassemia disorders in recent years, as well as in the practical aspects of prenatal diagnosis and clinical management. Alterations in a single or a few nucleotides account for most of the types of beta-thalassemia syndromes that have been characterized, and a variety of deletions have been found associated with beta O thalassemia, delta beta thalassemia, gamma delta beta thalassemia, and hereditary persistence of fetal hemoglobin (HPFH). Studies of nondeletional types of HPFH have revealed several single base changes 5' to the G gamma and A gamma genes, suggesting that these regions may be of major importance in the switchover from fetal to adult hemoglobin synthesis and in the relative production of the G gamma and A gamma globin chains during development. Evaluation of restriction enzyme polymorphisms and the assignment of haplotypes in the beta-like globin region of chromosome 11 have allowed delineation of the origin and distribution of thalassemia mutations, and have provided an important means for prenatal diagnosis. These studies have accumulated much new information about the function and expression of eukaryotic genes, and have served as a model for the investigation of human genetic disorders. The clinical management of patients with Cooley's anemia has benefited greatly from changes in transfusion practice, clear guidelines for splenectomy, and the availability of effective chelation therapy for iron overload. Current basic and clinical studies may lead to new approaches to management, treatment and eventual cures for this disease, including safe bone marrow transplantation, oral chelation treatment, and gene therapy.

Fetal Hemoglobin↗
PubMed1988

Non-random association of the Rsa I polymorphic site 5' to the beta-globin gene with major sickle cell haplotypes.

There are three main African haplotypes associated with the sickle mutation on chromosome 11. We have examined an Rsa I polymorphism 550 bp 5' to the beta-globin gene to study the degree of linkage disequilibrium between this Rsa I site and the three haplotypes. This Rsa I site is contained within the 10.3 kb or less area of randomization separating the 5'- and 3'-haplotype clusters. The beta S-containing chromosomes of the Benin and Senegal haplotypes are not cut, while those of the Central African Republic are cleaved by Rsa I at this site. Possible explanations of these findings are discussed.

Anemia, Sickle Cell↗
PubMed1988

A single-base change at position -175 in the 5'-flanking region of the G gamma-globin gene from a black with G gamma-beta+ HPFH.

Hereditary persistence of fetal hemoglobin (HPFH) is a human hemoglobinopathy characterized by the continued expression of fetal globins during adult life. Both deletional and nondeletional forms have been described. A number of single-base changes in the immediate 5'-flanking region of the fetal G gamma and A gamma have been reported associated with nondeletional forms of HPFH. We now present the nucleotide sequence of a G gamma-globin gene from an American black with G gamma-beta + HPFH. The immediate 5'-flanking region of this G gamma gene has a T-to-C change at -175, C at -158, and a normal C at -202. Additional changes were found in IVS2 and in the immediate 3'-flanking region, some of which may represent gene-conversion events. The sequence change at -175 probably represents a second mutation associated with the G gamma-beta + HPFH phenotype in blacks. This base change alters an octamer sequence known to be of importance in the normal expression of several other genes.

Base Sequence↗
PubMed1988

Globin gene expression in hereditary persistence of fetal haemoglobin and (delta beta) (0)-thalassaemia.

Recent advances in molecular and cell biology have led to major insights into understanding the regulation of globin gene expression in erythroid cells. Studies on HPFH and related syndromes have contributed much to this knowledge. Although no single explanation has emerged concerning the mechanism by which the deletional HPFH and (delta beta)(0)-thalassaemia affect HbF expression, they have led to new testable hypotheses to explain how different deletions result in similar phenotypes. The non-deletional HPFH and related syndromes have been the subject of recent intense interest, and a number of these disorders are now known to be associated with single-base changes in the promoter regions of one or the other fetal globin genes. If these base changes are causally related to the observed phenotypes, the molecular basis by which they increase HbF and simultaneously decrease HbA production remains to be determined. In addition, it has been recognized that other single-base changes 5' to the fetal-globin genes are associated with and may affect the phenotypic expression of certain forms of sickle-cell disease and beta-thalassaemia. Increased HbF production and high G gamma: A gamma ratios result in these individuals only under conditions of erythropoietic stress. The relationship between these point mutations and the cell biology of erythroid development clearly needs to be better delineated. Studies on HbF expression in humans will no doubt lead to elucidation of the mechanisms controlling the regulated expression of globin gene switching in normal and disease states, and hopefully, result in the design of molecular strategies for the amelioration of many of the human haemoglobinopathies.

Animals↗
PubMed1988

Rheologic predictors of the severity of the painful sickle cell crisis.

Deformable sickle erythrocytes have been reported by Mohandas and Evans to be more adherent to vascular endothelium than rigid irreversibly sickled cells (ISC). To define the clinical implications of this finding we have determined genetic, hematological, clinical, and rheological characteristics of sickle erythrocytes obtained from 65 patients with sickle cell anemia and fetal hemoglobin (Hb F) levels less than 15%. The alpha-globin gene number had a significant effect on the hematological parameters, the percentage of dense cells, ISC number, and HB A2 levels. The presence or absence of alpha thalassemia, however, had no effect on the frequency and severity of the sickle cell painful crisis (r = 0.06, P greater than .05). RBC deformability, determined by an ektacytometer, showed great heterogeneity among patients with three or four alpha-globin genes. Linear regression analyses of the data showed significant positive correlation of the frequency and severity of the painful crisis with RBC deformability (r = 0.49, P less than .001), and negative correlations with the percentage of dense cells (r = -0.37, P = .002), and the percentage of ISC (r = -0.46, P less than .001). We propose that the more deformable the sickle RBC are, the greater their adherence to vascular endothelium, and the more they cause vaso-occlusive crises, RBC deformability and the percentage of dense cells (or ISC) seem to have a predictive value of the frequency and severity of painful crises in sickle cell anemia.

Adolescent↗
PubMed1987

DNA methylation in hereditary persistence of fetal hemoglobin (HPFH-2).

Recent studies show that the region of DNA brought into close proximity to the fetal gamma-globin genes in deletional forms of hereditary persistence of fetal hemoglobin (HPFH) is selectively hypomethylated (and presumably active) in normal erythroid tissue. This region is normally located approximately 100 kilobases (kb) 3' to the fetal genes. The continued expression of fetal hemoglobin in adult life in these forms of HPFH has been ascribed to the effect of this erythroid-specific region in altering local chromosomal structure and allowing transcription. Because transcriptional activity is often associated with hypomethylation, we have examined the methylation status of the gamma-globin genes and the truncated psi beta gene on the HPFH chromosome to determine whether juxtaposition of this erythroid-specific region results in a generalized hypomethylation of the globin gene region upstream of the deletion breakpoint. Genomic DNA purified from nucleated red blood cells (nRBC) from a patient with HPFH-2/beta O thalassemia was digested with Msp I or Hpa II, and the methylation pattern determined on the HPFH chromosome by using secondary cleavage with restriction enzymes which span the deletion breakpoint. These studies show that in nRBC the HPFH-2 chromosome is hypomethylated in the 3'-juxtaposed region (3'JR) and in the region of the gamma-globin genes. In contrast, Msp I sites near the truncated psi beta-globin gene remain methylated, suggesting that only a subset of CpG sites upstream from the 3'JR become hypomethylated in HPFH-2. This subset of sites corresponds to those which are normally hypomethylated when fetal genes are active. The continued high level of fetal globin expression is, therefore, not associated with a generalized hypomethylation upstream from the deletion junction.

DNA↗
PubMed1987

Structure of the platelet membrane glycoprotein IIb. Homology to the alpha subunits of the vitronectin and fibronectin membrane receptors.

The platelet membrane glycoprotein IIb X IIIa heterodimer complex (GPIIb X IIIa) is the platelet receptor for adhesive proteins, containing binding sites for fibrinogen, von Willebrand factor, and fibronectin on activated platelets. GPIIb X IIIa also appears to be a member of a family of membrane adhesive protein receptors that plays a major role in cell-cell and cell-matrix interactions. GPIb is the larger component of this platelet receptor and is composed of two disulfide-linked subunits. In this report we describe the analysis of cDNA clones for human GPIIb that were isolated from a lambda gt11 expression library prepared using RNA from HEL cells. A total of 3.3 kilobases of cDNA was sequence, revealing a continuous open reading frame encoding both GPIIb subunits. The cDNA encodes 1039 amino acids: 137 constituting the smaller subunit, 871 constituting the larger subunit, and 30 constituting an NH2-terminal signal peptide. No homology was found between the larger and smaller subunits. The smaller subunit contains a 26-residue hydrophobic sequence near its COOH terminus that represents a potential transmembrane domain. Four stretches of 12 amino acids present in the larger subunit are homologous to the calcium binding sites of calmodulin and troponin C. Northern blot analysis using HEL cell RNA indicated that the mature mRNA coding for GPIIb is 4.1 kilobases in size. A comparison of the GPIIb coding region with available cDNA sequences of the alpha-chains of the vitronectin and fibronectin receptors revealed 41% DNA homology and 74% and 63% amino acid homology, respectively. Our data establish the amino acid sequence for the human platelet glycoprotein IIb and provide additional evidence for the existence of a family of cellular adhesion protein receptors.

Amino Acid Sequence↗