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Biomedical subjects

P Gane

Publications and source records attributed to P Gane.

At least 37 records · Page 2Linked to original sources
PubMed1998

High adenosine deaminase level among healthy probands of Diamond Blackfan anemia (DBA) cosegregates with the DBA gene region on chromosome 19q13. The DBA Working Group of Société d'Immunologie Pédiatrique (SHIP).

Phenotypic characterization of Diamond Blackfan Anemia (DBA) patients and their relatives was performed in 54 families. Complete blood count, fetal hemoglobin level, erythrocyte i antigen expression, and erythrocyte adenosine deaminase (eADA) activities were quantitated in patients and relatives. eADA was elevated in 28 of 34 transfusion-independent DBA patients, whereas persistence of erythrocyte i antigen was noticed in only 10 of 20 DBA patients. High eADA activities were also found in 14 of 149 healthy family members, allowing us to identify an isolated high eADA phenotype in these families. In contrast, increase in erythrocyte i antigen expression, elevated fetal hemoglobin levels, and macrocytosis were much less frequently noted in nonaffected members of the DBA families studied. Importantly, isolated high eADA phenotype was found to be significantly associated with genetic markers on chromosome 19 that segregate with the DBA phenotype. Isolated high eADA phenotype thus seems to reflect a silent phenotype of DBA in affected families. These findings suggest that elevated eADA activity in unaffected individuals needs to be taken into account during genetic assessment of DBA families and could be used for accurate assessment of mode of inheritance.

Adenosine Deaminase↗
PubMed1998

Rh-deficiency of the regulator type caused by splicing mutations in the human RH50 gene.

The Rh polypeptides and the glycoproteins Rh50, CD47, LW, and glycophorin B, which interact in the red blood cell membrane to form a multisubunit complex, are lacking or are severely reduced in the Rh-deficiency syndrome. We previously reported that in several Rhnull patients the RH50 gene was altered at the coding sequence level, resulting in either a single amino acid substitution or the synthesis of a truncated polypeptide. In the present report, we have detected two mutations in the intronic region of the RH50 gene that identify a new molecular mechanism involved in Rh-deficiency. The first mutation affected the invariant G residue of the 3' acceptor splice-site of intron 6, causing the skipping of the downstream exon and the premature termination of translation. The second mutation occurred at the first base of the 5' donor splice-site of intron 1. Both these mutations were found in homozygote state. RNase protection assays demonstrated that the Rh50 mRNA level was strongly reduced or undetectable in the 3' and 5' splice mutants, respectively. The different mutations affecting the RH50 gene are indicative of an heterogeneous mutational pattern, which further supports the hypothesis that the lack of the Rh50 protein may prevent the assembly or transport of the Rh membrane complex to the red blood cell surface.

Amino Acid Sequence↗
PubMed1998

Arg89Cys substitution results in very low membrane expression of the Duffy antigen/receptor for chemokines in Fy(x) individuals.

The Duffy (FY) blood group antigens are carried by the DARC glycoprotein, a widely expressed chemokine receptor. The molecular basis of the Fya/Fyb and Fy(a-b-) polymorphisms has been clarified, but little is known about the Fyx antigen and the FY*X allele associated with weak expression of Fyb, Fy3, Fy5, and Fy6 antigens. We analyzed here the structure and expression of the FY gene in 4 Fy(a-bweak) individuals. As compared with Fy(a-b+) controls, the Fy(a-bweak) red blood cell membranes contained residual amount of DARC polypeptide and these cells were poorly bound by anti-Fy antibodies and chemokines. The FY gene from Fy(a-b+) and Fy(a-bweak) individuals differed by one substitution, C286T. The resulting Arg89Cys amino acid change reduced the binding of anti-Fy antibodies and chemokines to DARC transfectants. We concluded that the Fybweak donors carried the FY*X allele at the FY locus and that the Fyx antigen corresponds to highly reduced expression of a grossly normal Fyb polypeptide caused by the Arg89Cys substitution. Because FY is a single copy gene, this defect should also affect DARC expression in nonerythroid cells. Because the Fyx phenotype is not associated with apparent clinical consequences, we discussed these findings in the light of the putative roles of DARC in various tissues. Finally, we developed a Fyx DNA typing assay that should be useful for genetic studies and clinical transfusion medicine.

Alleles↗
PubMed1998

Molecular defects of the RHCE gene in Rh-deficient individuals of the amorph type.

The deficiency of Rh proteins on the red blood cells from individuals of the Rhnull amorph type may be the result of homozygosity for a silent allele at the RH locus. This phenotype is also associated with the lack or reduced expression of glycoproteins (Rh50, CD47, LW, and glycophorin B), which interact with Rh polypeptides to form the multisubunit Rh membrane complex. In this study, we describe two molecular alterations affecting the RHCE gene in two unrelated Rhnull amorph individuals bearing Rh50 and CD47 normal transcripts. The first type of mutation, located at the donor splice-site in intron 4, induced the activation of two cryptic splice-sites within this intron and one such site in exon 4 that all generated aberrant transcripts. The second type of mutation affected the coding region and introduced a frameshift and a premature stop codon resulting in a shorter predicted protein (398 v 417 residues), including a completely different C-terminus of 76 amino acids. This suggests that protein folding and/or protein-protein interaction mediated by the C-terminal domain of the Rh proteins may play a role in the routing and/or stability of the Rh membrane complex.

Alleles↗
PubMed1998

The Lutheran blood group glycoproteins, the erythroid receptors for laminin, are adhesion molecules.

The Lutheran antigens are recently characterized glycoproteins in which the extracellular region contains five immunoglobulin like domains, suggesting some recognition function. A recent abstract suggests that the Lutheran glycoproteins (Lu gps) act as erythrocyte receptors for soluble laminin (Udani, M., Jefferson, S., Daymont, C., Zen, Q., and Telen, M. J. (1996) Blood 88, Suppl. 1, 6 (abstr.)). In the present report, we provided the definitive proof of the laminin receptor function of the Lu gps by demonstrating that stably transfected cells (murine L929 and human K562 cell lines) expressing the Lu gps bound laminin in solution and acquired adhesive properties to laminin-coated plastic dishes but not to fibronectin, vitronectin, transferrin, fibrinogen, or fibrin. Furthermore, expression of either the long-tail (85 kDa) or the short-tail (78 kDa) Lu gps, which differ by the presence or the absence of the last 40 amino acids of the cytoplasmic domain, respectively, conferred to transfected cells the same laminin binding capacity. We also confirmed by flow cytometry analysis that the level of laminin binding to red cells is correlated with the level of Lu antigen expression. Indeed, Lunull cells did not bind to laminin, whereas sickle cells from most patients homozygous for hemoglobin S overexpressed Lu antigens and exhibited an increased binding to laminin, as compared with normal red cells. Laminin binding to normal and sickle red cells as well as to Lu transfected cells was totally inhibited by a soluble Lu-Fc chimeric fragment containing the extracellular domain of the Lu gps. During in vitro erythropoiesis performed by two-phase liquid cultures of human peripheral blood, the appearance of Lu antigens in late erythroid differentiation was concomitant with the laminin binding capacity of the cultured erythroblasts. Altogether, our results demonstrated that long-tail and short-tail Lu gps are adhesion molecules that bind equally well laminin and strongly suggested that these glycoproteins are the unique receptors for laminin in normal and sickle mature red cells as well as in erythroid progenitors.

Animals↗
PubMed1998

Shift from Rh-positive to Rh-negative phenotype caused by a somatic mutation within the RHD gene in a patient with chronic myelocytic leukaemia.

We report a female patient whose Rh phenotype shifted from RhD-positive to RhD-negative over a 3-year period (1991-94), during which time she was treated with mastectomy (1992) and local irradiation for a low-grade recurrent breast cancer. She was diagnosed with chronic myeloid leukaemia in 1994, and has since then received chemotherapy. The patient was repeatedly typed as O, RhD-positive between 1965 and 1991 and was repeatedly found RhD-negative after 1994. Bcr-Abl transcripts typical of Ph1 chromosome were detected. Molecular analysis indicated that the patient was heterozygous at the RH locus, carrying one haplotype in which the RHD gene exhibited a single nucleotide deletion (G600) resulting in a frameshift and premature stop codon, and a normal RHCE gene (allele Ce). The second haplotype contained only the RHCE gene (allele ce) and was normal. Further analysis carried out on total leucocytes, purified neutrophils, EBV-lymphoblastoid cell line and cultured erythroblasts indicated that the G600 deletion was restricted to the myeloid lineage. No modification of other blood group antigens could be detected. These findings suggest a somatic mutation which most probably occurred in a stem cell common to the myeloid lineage.

Aged↗
PubMed1998

Heterogeneity of blood group RhE variants revealed by serological analysis and molecular alteration of the RHCE gene and transcript.

After testing red cells from 12 RhE variants with a panel of anti-E monoclonal antibodies (MoAbs), four patterns of reactivity were detected indicating that the MoAbs may recognize four distinct E epitopes designated epE1, epE2, epE3 and epE4. The variants were classified into four categories (cat EI to EIV) which carried epE1 and epE2, epE1 and epE4, epE1, epE3 and epE4, and all four epitopes, respectively. Molecular analysis of the transcripts and genomic DNA of the variants from cat EI, EII and EIII displayed three distinct genetic alterations. Cat EI variants exhibited a point mutation (T500A) in exon 4 of the RHCE gene that resulted in a Met167Lys substitution in the third extracellular loop of the RhcE protein. Cat EII variant carried a hybrid gene structure characterized by replacement of exons 1-3 (or 2-3) of the RHCE gene by their specific counterparts in the RHD gene. This latter variant was also associated with a weak expression of the RhC antigen. In cat EIII variants there was a partial DNA exchange of exon 5 sequences (nt 697 and 712) between the RHCE and the RHD genes, generating a hybrid Rh cE-D-cE protein carrying the Glu233 and Val238 substitutions. The serological and molecular studies of the RhE variants indicated that: (i) the RhE antigen is a mosaic composed of at least four epitopes and proline at position 226 is necessary but not sufficient for the full expression of the E antigen, (ii) the lack of RhE epitope(s) is associated with heterogenous molecular alterations of the RHCE gene, and (iii) amino-acids located on the third and fourth extracellular loops of the RhCE polypeptide are critical for some RhE epitopes expression.

Antibodies, Monoclonal↗
PubMed1997

IL-13 induces CD34+ cells isolated from G-CSF mobilized blood to differentiate in vitro into potent antigen presenting cells.

Dendritic cells (DCs), which are antigen presenting cells of potential use in human antitumor vaccination trials, are presently the subject of intense investigation. Many recent studies have reported the possibility of generating ex vivo large numbers of DCs with high antigen presenting capacity by the culture of bone marrow or blood progenitors. In this study, we examined the differentiation into DCs of CD34+ progenitors isolated from the G-CSF mobilized blood of 3 healthy donors and 5 patients with breast cancer and cultured in the presence of GM-CSF + IL-13. The characteristics of the cells were compared to those of cells obtained in the presence of GM-CSF + TNF alpha. By day 15, one third of the bulk cells cultured with IL-13 were CD1a+/CD14- and strongly expressed CD1c, CD40, CD80 and HLA-DR. In contrast, cells obtained with TNF alpha expressed CD1a on one in three cells but with a considerably lower fluorescence intensity than on IL-13-cultured cells and strongly expressed CD14 on more than 50% of cells. CD1a+/CD14- cells emerged in IL-13 cultures at day 5, while in TNF alpha cultures CD14+ cells appeared before CD1a+ cells. Cells grown in the presence of IL-13 had an increased capacity to present antigens to autologous lymphocytes and to stimulate allogeneic T-lymphocytes. This effect was greater than that of cells grown in the presence of TNF alpha. These cells should therefore have greater effector potential in any therapeutic applications in humans.

Animals↗
PubMed1997

Close association of the first and fourth extracellular domains of the Duffy antigen/receptor for chemokines by a disulfide bond is required for ligand binding.

It has been demonstrated that the promiscuous chemokine binding profile of the Duffy antigen/receptor for chemokines (DARC) is given by its extracellular NH2-terminal region. However, the relationship among the Fy6, Fya/b, and Fy3 epitopes, localized in the first and fourth extracellular domains of DARC, respectively, and the chemokine binding sites remained a matter of controversy. Here, we performed cross-displacement and cross-inhibition experiments indicating that all anti-Fy6, anti-Fya, and anti-Fy3 monoclonal antibodies and interleukin 8 are antagonists for binding to red cells. Biopanning of phage peptide libraries with an anti-Fy6 monoclonal antibody led to the identification of the motif Phe22-Glu23, the mutation of which altered the binding of both anti-Fy6 and chemokines (interleukin 8, MGSA, RANTES (regulated on activation normal T cell expressed)) to DARC transfectants. These results characterized the core of the Fy6 epitope and provided definitive proof of the tight relationship between Fy6 and the chemokine receptor site. Analysis of red cells treated by sulfhydryl group-modifying reagents suggested that the chemokine receptor function of DARC required the integrity of disulfide bond(s) but not that of free sulfhydryl group(s). Accordingly, mutation of cysteines 51 and 276 abolished chemokine binding to DARC transfectants. Altogether, our results suggested that the chemokine binding pocket of DARC included sequences located in the first and fourth extracellular domains which are brought into close vicinity by a disulfide bridge.

Amino Acid Sequence↗
PubMed1997

Organization of the human LU gene and molecular basis of the Lu(a)/Lu(b) blood group polymorphism.

The Lutheran (Lu) blood group antigens and the B-cell adhesion molecule (B-CAM) epithelial cancer antigen are carried by recently cloned integral glycoproteins that belong to the Ig superfamily. We have previously shown that the Lu and B-CAM antigens are encoded by the same gene, LU, and that alternative splicing of the primary transcript most likely accounts for the presence of both antigens on two isoforms that differ by the length of their cytoplasmic tails. In the present report, we isolated the human LU gene by cloning a 20-kb HindIII fragment from Lu(a - b+) genomic DNA. The LU gene is organized into 15 exons distributed over 12.5 kb. Alternative splicing of intron 13 generates the 2.5- and 4.0-kb transcript spliceoforms encoding the long tail and the short tail Lu polypeptides, respectively. Sequencing of the major mRNA species (2.5 kb) amplified from human bone marrow, kidney, placenta, and skeletal muscle did not suggest the presence of tissue-specific Lu glycoprotein isoforms. The same transcription initiation point, located 22 bp upstream from the initiation codon, was characterized in several tissues. In agreement with the wide tissue distribution of the Lu messengers, the GC-rich proximal 5' flanking region of the LU gene does not contain TATA or CAAT boxes, but includes several potential binding sites for the ubiquitous Sp1 transcription factor. In addition, the distal 5' region, encompassing nucleotides -673 to -764, contains clustered binding sequences for the GATA, CACCC, and Ets transcription factors. Analysis of the coding sequences amplified from genomic DNA of Lu(a + b-) or Lu(a - b+) donors showed a single nucleotide change in exon 3 (A229G) that correlates with an Aci I restriction site polymorphism and results in a His77Arg amino-acid substitution. Polymerase chain reaction/restriction fragment length polymorphism analysis indicated that the A229G mutation is associated with the Lu(a)/Lu(b) blood group polymorphism. When expressed in Chinese hamster ovary (CHO) cells, Lu cDNAs carrying the A229 or the G229 produced cell surface proteins that reacted with anti-Lu(a) or anti-Lu(b) antibodies, respectively, showing that these nucleotides specify the Lu(a) and Lu(b) alleles of the Lutheran blood group locus. CHO cells expressing recombinant short-tail or long-tail Lu glycoproteins reacted as well with anti-Lu as with anti-B-CAM antibodies, providing the definitive proof that the Lu blood group and B-CAM antigens are carried by the same molecules.

Alleles↗
PubMed1996

Molecular basis of the altered antigenic expression of RhD in weak D(Du) and RhC/e in RN phenotypes.

The RH blood group locus is composed of two sequence-related genes, RHD and RHCE, encoding the D, Cc, and Ee antigens in common Rh-positive phenotypes. In this report, we have analyzed the molecular basis of Rh antigens expression in weak D (Du) and RN donors, in whom there is a severe reduction of the D and C/e antigens, respectively. Genomic and transcript analysis of three unrelated low-grade weak D (Du) variants indicated that the very low expression of the D antigen is not the result of rearrangement or mutation in the coding sequence of the RHO gone. Accordingly, weak D (Du) erythrocytes should carry a normal RhD polypeptide, which is in agreement with the observation that these variants never produce anti-D antibodies. Comparative polymerase chain reaction analysis showed a lower steady-state level of RhD transcripts in weak D (Du) reticulocytes, as compared with normal RhD-positive controls, thus providing direct evidence that the difference between the D antigen of D-positive and weak D (Du) red blood cells is quantitative only. Conversely, analysis of the molecular genetic basis of the RN phenotype Indicated that the severely decreased expression of the RhC and Rhe antigens in three variants is associated with a qualitative alteration identified as a segmental DNA exchange between the RHCE and RHD genes. These genomic rearrangements, which resulted in hybrid RhCe-D-Ce proteins expressing the low frequency Rh32 but not the high incidence Rh46 antigens, involved either axon 4 alone or both exons 3 and 4. These findings show that an identical phenotypical alteration of Rh antigens (reduced expression) may result either from a quantitative or a qualitative alteration of the RH genes expression.

Alleles↗
PubMed1996

Recognition of the blood group H type 2 trisaccharide epitope by 28 monoclonal antibodies and three lectins.

The patterns of cross-reaction of 30 monoclonal antibodies and three lectins were determined by ELISA with 21 ABH, Ii or Lewis related synthetic oligosaccharides coupled to bovine serum albumin. At least seven main groups of cross-reactive patterns were identified among the antibodies, plus several isolated antibodies which had intermediate patterns between two of the main antibody groups. The three lectins had different cross-reaction patterns, Galactia tenuiflora was different from all the antibodies, Ulex europaeus lectin 1 and Lotus tetragonolobus were similar, but not identical to groups III and V of antibodies respectively. The anti-H antibodies cross-reacting with A type 2 gave similar agglutination scores with all the normal ABO erythrocytes, while the anti-H antibodies not cross-reacting with A type 2 reacted with different scores: O > A2 > A2B > B > A1 > A1B > O(h), suggesting that these antibodies react better with the free H epitopes and do not recognize the H in A or B epitopes. Based on the ELISA and agglutination results and the lowest energy conformations of each oligosaccharide obtained by computer modelling, the most probable oligosaccharide surface areas recognized by each antibody main group are illustrated.

ABO Blood-Group System↗
PubMed1996

Non Hodgkin's lymphoma presenting as neutropenia related to an IgM monoclonal anti-i antibody.

A sixty-year old female was referred to the Internal Medicine Department for the treatment of a diffuse high-grade non Hodgkin's lymphoma. She presented episodes of fever in context of neutropenia (neutrophils 0.35 x 10(9)/1 from 1.6 x 10(9)/1 white blood cells). Hemoglobin level was 8.2 g/dl and platelets 132 x 10(12)/1. A monoclonal IgM-Kappa protein (48 g/l) was detected in her serum. A direct antiglobulin test on the red cells proved positive with anti-C3d but not with anti-IgG antiglobulin, due to the presence of an IgM cold antibody with a serological anti-i specificity. The IgM antibody was found on the patient's neutrophils as well as in her serum. The antibody recognized all neutrophils tested in conventional serological tests whether the neutrophil phenotypes in systems NA, NB, and 5. It was demonstrated that it recognized the i antigen expressed on the neutrophils. These results suggest that a cold agglutinin anti-i might be responsible for neutropenia in some patients.

Antibodies, Anti-Idiotypic↗
PubMed1996

Flow cytometric evaluation of non anti-RH1(D) monoclonal Rh antibodies.

IgG non anti-RH1(D) monoclonal Rh antibodies were evaluated by flow cytometry. The values obtained with these antibodies were less strong than those obtained with anti-RH1(D) antibodies. For a significant number of antibodies, the signal was not high enough to give reliable results for the antibody specificity. Despite these drawbacks, flow cytometry was an efficient tool to appreciate the variation of reactivity by different antibodies with normal or variant cells. These variations were not always obvious by serological means.

Animals↗
PubMed1996

Candidate gene acting as a suppressor of the RH locus in most cases of Rh-deficiency.

The Rh antigen is a multi-subunit complex composed of Rh polypeptides and associated glycoproteins (Rh50, CD47, LW and glycophorin B); these interact in the red cell membrane and are lacking or severely reduced in Rhnull cells. As a result, individuals with Rhnull suffer chronic haemolytic anaemia known as the Rh-deficiency syndrome. Most frequently, Rhnull phenotypes are caused by homozygosity of an autosomal suppressor gene unlinked to the RH locus (Rhnull regulator or Rhmod types). We have analysed the genes and transcripts encoding Rh, CD47 and Rh50 proteins in five such unrelated Rhnull cases. In all patients, we identified alteration of Rh50--frameshift, nucleotide mutations, or failure of amplification--which correlated with Rhnull phenotype. We propose that mutant alleles of Rh50, which map to chromosome 6p11-21.1, are likely candidates for suppressors of the RH locus accounting for most cases of Rh-deficiency.

Amino Acid Sequence↗
PubMed1996

Molecular analysis of blood group Rh transcripts from a rGr variant.

The Rh blood group antigens D, Cc and Ee are encoded by two related genes, RHD and RHCE. The RhG antigen (Rh12) is associated with the expression of RhC and/or RhD, except in rare variant red cells. Here we have determined the molecular basis of G expression in the absence of D and C in the rGr phenotype. Nucleotide sequence analysis revealed that the rG allele resulted either from a segmental DNA exchange between part of exon 2 of the RHce gene and the equivalent region of the RHCE or RHD genes or from a crossing over between positions nt150 and nt178 of the RHce and RHCe genes. The predicted protein encoded by the hybrid rG gene (c-C-e or c-D-e) carries Ile60, Ser68 and Ser103 (as C and D polypeptides); any of these positions appear to be critical in the formation of the G antigen. In addition, Cys16 was found to be important in the phenotypic expression of C.

Base Sequence↗
PubMed1995

Molecular basis and expression of the LWa/LWb blood group polymorphism.

The Landsteiner-Wiener (LW) blood group antigens reside on a 42-kD erythrocyte membrane glycoprotein that has recently been cloned. Here, we found that the molecular basis for the LWa/LWb polymorphism is determined by a single base pair mutation (A308G) that correlates with a Pvu II restriction site and results in a Gln70Arg amino acid substitution. COS-7 cells transfected with LWa or LWb cDNAs reacted with human anti-LWa and anti-LWb sera, respectively, as well as with a murine monoclonal anti-LWab antibody, as shown by flow cytometry analysis. Moreover, a 42-kD protein was immunoprecipitated from the transfected cells with the monoclonal anti-LWab antibody. These findings indicate that LWa and LWb are alleles of the LW blood group locus as defined also by a monoclonal anti-LWab of nonhuman origin. In addition, the LW locus has been assigned to chromosome 19p13.3 by in situ hybridization. Study by Southern blot analysis indicated also that the LW locus is composed of a single gene that was not grossly rearranged in rare LW(a-b-) and Rhnull individuals deficient for LW antigens. In addition, Pvu II restriction fragment-length polymorphism analysis indicated that these variants were all homozygous for a phenotypically silent LWa allele.

Alleles↗