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H J Garchon

Publications and source records attributed to H J Garchon.

At least 37 records · Page 2Linked to original sources
PubMed1997

No evidence for an association of AChR beta-subunit gene (CHRNB1) with myasthenia gravis.

Using a polymorphic dinucleotide repeat, we have investigated the contribution of the gene encoding the beta-subunit of the muscle acetylcholine receptor (CHRNB1), the target autoantigen, to the susceptibility to myasthenia gravis (MG). We have combined a case-control study (comparing 143 patients and 162 controls) and a transmission-disequilibrium test bearing on 35 simplex families with heterozygous parents. There was no evidence for an association of CHRNB1 with MG, even after subgrouping patients according to thymus histology, or other clinical criteria. Interestingly however, the shortest four variants of the CHRNB1 microsatellite were seen only in patients with thymus hyperplasia and in none of the control subjects (P < 0.0025).

Adult↗
PubMed1997

Recurrent mutations in a single exon encoding the evolutionarily conserved olfactomedin-homology domain of TIGR in familial open-angle glaucoma.

Primary open-angle glaucoma (POAG) is a highly prevalent cause of irreversible blindness which associates cupping of the optic disc and alteration of the visual field, elevation of intraocular pressure being a major risk factor. Provided diagnosis is made at an early stage, treatments are available to prevent visual impairment. A locus, GLC1A, has been mapped on chromosome 1q23-q25 in several families affected with juvenile-onset POAG (JOAG) and also in some families affected with juvenile and middle-age onset POAG. Recently, three mutations of the TIGR (Trabecular meshwork-Induced Glucocorticoid Response) gene were shown to be responsible for the disease in several American families and in unrelated POAG patients. We now describe five new mutations in eight French families. All mutations known to date appear to concentrate in the evolutionarily conserved C-terminal domain of TIGR which bears homology to frog olfactomedin, an extracellular matrix glycoprotein of the olfactory epithelium, to rat and human neuronal olfactomedin-related proteins and to F11C3.2, a protein from Caenorhabditis elegans . Moreover, this conserved domain of TIGR is encoded by a single exon to which mutation screening could be limited. Surprisingly, the TIGR message, which is abundantly transcribed in the trabecular meshwork and also in the ciliary body and the sclera, is not expressed in the optic nerve whose degeneration is, however, the primary lesion of POAG.

Adolescent↗
PubMed1997

Insulin-dependent diabetes mellitus (IDDM) is associated with CTLA4 polymorphisms in multiple ethnic groups.

Linkage disequilibrium (association) analysis was used to evaluate a candidate region near the CTLA4/CD28 genes using a multi-ethnic collection of families with one or more children affected by IDDM. In the data set unique to this study (Spanish, French, Mexican-American, Chinese and Korean), the transmission/disequilibrium test (TDT) revealed a highly significant deviation for transmission of alleles at the (AT)n microsatellite marker in the 3' untranslated region (P = 0.002) and the A/G polymorphism in the first exon (P = 0.00002) of the CTLA4 gene. The overall evidence for transmission deviation of the CTLA4 A/G alleles is also highly significant (P = 0.00005) in the combined data set (669 multiplex and 357 simplex families) from this study and a previous report on families from USA, Italy, UK, Spain and Sardinia. Significant heterogeneity was observed in these data sets. The British, Sardinian and Chinese data sets did not show any deviation for the A/G polymorphism, while the Caucasian-American data set showed a weak transmission deviation. Strong deviation for transmission was seen in the three Mediterranean-European populations (Italian, Spanish and French) (P = 10(-5)), the Mexican-American population (P = 0.002) and the Korean population (P = 0.03). These results suggest that a true IDDM susceptibility locus (designated IDDM12) is located near CTLA4.

Abatacept↗
PubMed1997

Molecular genetics of open-angle glaucoma, moving from gene localization to predictive testing.

It has long been suspected that genetic factors play a role in open-angle glaucoma. Only recently, however, has the molecular basis of such factors begun to be established, with the primary localization of the GLC1A locus for juvenile-onset and early-onset autosomal dominant open-angle glaucoma on chromosome 1q. These findings are clinically significant in that they allow familial screening of individuals at risk for glaucoma before the onset of irreversible visual impairment. A physical map of the GLC1A genomic region is now available, and the actual GLC1A gene might be identified in the near future. Nevertheless, open-angle glaucoma is a genetically heterogeneous entity, and additional loci have been mapped or proposed. Identification of open-angle glaucoma genes should provide invaluable clues to the disorder's pathophysiology. It could also aid in conceiving novel therapeutic agents and broadening the screening of at-risk subjects.

Chromosome Mapping↗
PubMed1997

Genetic heterogeneity of primary open angle glaucoma and ocular hypertension: linkage to GLC1A associated with an increased risk of severe glaucomatous optic neuropathy.

The GLC1A locus for autosomal dominant juvenile and middle age onset primary open angle glaucoma (OAG) has been mapped to chromosome 1q21-q31. OAG, however, is a heterogeneous disease. We tested linkage of OAG and ocular hypertension (OHT), a major risk factor for OAG, to GLC1A in eight French families with multiple cases of juvenile and middle age onset OAG. There was strong evidence of genetic heterogeneity, four families being linked to GLC1A and two or three others being unlinked, depending on whether the complete OAG phenotype was analysed alone or jointly with OHT. Peak intraocular pressure (IOP) did not differ significantly between the two groups of families, while linkage to GLC1A conferred a highly increased risk of developing OAG and of having severe glaucomatous optic neuropathy. Testing linkage of familial OAG to GLC1A may therefore have prognostic value too.

Adult↗
PubMed1996

Defective Fc gamma RII gene expression in macrophages of NOD mice: genetic linkage with up-regulation of IgG1 and IgG2b in serum.

A quantitative trait locus for increased IgG serum levels in the NOD mouse strain was mapped to distal chromosome 1, close to the fcgr2 locus encoding the low-affinity type II receptor for the Fc portion of IgG (Fc gamma RII). Expression of membrane-inserted (b2) and soluble (b3) isoforms of Fc gamma RII was strongly decreased in macrophages of NOD compared with C57BL/6 (B6) mice. In contrast, B cell-specific (Fc gamma RIIb1) isoform was only slightly decreased and Fc gamma RIII was not altered. This Fc gamma RII regulatory defect was cis-encoded by fcgr2 or by a closely linked locus, occurred at the mRNA level, and was associated with multiple mutations in the fcgr2 gene promoter. In relation with this defect, binding of IgG1- and IgG2b- but not IgG2a-opsonized RBC by macrophages of NOD and congenic B6.NOD-fcgr2 mice was severely impaired, but was normal in macrophages of NOD.B6-fcgr2 congenic mice, indicating that Fc gamma RII plays a nondispensable role in binding of IgG1 and IgG2b isotypes. Likewise, serum levels of IgG1 and IgG2b but not IgG2a were up-regulated in NOD compared with NOD.B6-fcgr2 congenic mice. These findings indicate that macrophage Fc gamma RII may regulate serum IgG1 and IgG2b through their catabolism, and validate the NOD strain as a model to investigate the functions of Fc gamma RII isoforms.

Animals↗
PubMed1996

Distribution of HLA class II alleles and haplotypes in insulin-dependent Moroccan diabetics.

HLA class II polymorphism in Moroccan IDDM patients has not been investigated so far. In this study, HLA-DRB1, -DQA1, and -DQB1 allele and haplotype frequencies were analyzed in 125 unrelated Moroccan IDDM patients and 93 unrelated healthy controls, all originating from the Souss region and mostly of Berber origin. Some common features with other Caucasian groups were observed, in particular, a predisposing effect of the DRB1*03-DQA1*0501-DQB1*0201 and DRB1*04-DQA1*0301-DQB1*0302 alleles or allelic combinations. The Moroccan IDDM group also presented with more specific characteristics. Among DRB1*04 subtypes, DRB1*0405 was associated with susceptibility to and DRB1*0406 with protection from the disease. The haplotype and the relative predispositional effect (RPE) analyses indicated that the DRB1*08-DQA1*0401-DQB1*0402 haplotype was also associated with susceptibility to IDDM. Interestingly, the DRB1*09-DQA1*0301-DQB1*0201 haplotype, completely absent from the control group and very rare in North African populations, was observed in 7.2% of the Moroccan diabetics. Conversely, the DRB1*07-DQA1*0201-DQB1*0201 and DRB1*15-DQA1*0102-DQB1*0602 haplotypes were associated with protection from IDDM. Finally, we observed an age-dependent genetic heterogeneity of IDDM, the frequencies of predisposing alleles being higher and those of protective alleles lower in childhood- than in adult-onset diabetics. Our data on Moroccan diabetics, together with data on European and Northern Mediterranean patients, suggest a gradient of various HLA class II predisposing and protective markers that link these populations.

Adolescent↗
PubMed1996

Age-dependent penetrance and mapping of the locus for juvenile and early-onset open-angle glaucoma on chromosome 1q (GLC1A) in a French family.

The GLC1A locus for autosomal dominant primary open-angle glaucoma (POAG) with juvenile onset (before 20 years) has been mapped to chromosome 1q21-q31. Recently, a French-Canadian family was described in which both juvenile-onset and middle-age or early-onset POAG were observed and linked to GLC1A. We now describe a second POAG family with variable age of onset (range 11-51, median 36 years of age). Linkage to GLC1A was established with a maximum lod score of 6.21 at the D1S452 locus. A recombination event in a severely glaucomatous patient restricted the distal boundary of the GLC1A interval proximal to the AFM154xc9 marker. This study strengthens the idea that early-onset POAG may also be determined by the GLC1A genetic region.

Adolescent↗
PubMed1996

Apoptosis as a mechanism of keratinocyte death in toxic epidermal necrolysis.

Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are life-threatening diseases characterized by extensive epidermal destruction. The aim of our study was to investigate apoptosis in keratinocytes of patients with TEN and TEN/SJS overlap syndrome. Keratinocytes from TEN patients were found to undergo extensive apoptosis. These results suggest that cell destruction in TEN occurs as a result of apoptosis. Our findings suggest that apoptosis inhibitory agents may play an important part in the therapeutic strategy of TEN.

Adult↗
PubMed1995

A putative human equivalent of the murine Xlr (X-linked, lymphocyte-regulated) protein.

The murine Xlr (X-linked, lymphocyte-regulated) gene family was originally identified by subtractive cDNA hybridization and cloning. It was found to encode two 30-kDa nuclear proteins expressed in lymphoid cells and in primary spermatocytes in a developmentally regulated manner. Our data show that, in contrast to most X-linked genes, the Xlr family is not conserved at the DNA level between mouse and human. However, using anti-Xlr antibodies, an Xlr-immunoreactive nuclear protein of M(r) 30,000 was characterized in human RAJI B-lymphoblastoid cells by flow cytofluorimetry, by immunoblotting, and by immunocytolabeling. An Xlr-like molecule was also found to be expressed in human activated lymphocytes and in human primary spermatocytes, with a stage specificity similar to that known in the mouse. In contrast, no Xlr-immunoreactive protein was detected in a series of human tissues including brain, skeletal muscle, colon, liver, and kidney, revealing a tissue-specific expression pattern similar to that of murine Xlr. These findings most likely identify a human equivalent of Xlr. The Xlr genes belong to a small category of X-linked genes, including STS, MIC2, CSF2RA, and KAL, that diverge at the DNA level in human and in mice. Characterization of the human XLR gene(s) should now be feasible with anti-Xlr antibodies and an expression cloning system. It should provide new insights into the evolution of mammalian X Chromosome (Chr).

Animals↗
PubMed1995

Family study of linkage disequilibrium between TAP2 transporter and HLA class II genes. Absence of TAP2 contribution to association with insulin-dependent diabetes mellitus.

The polymorphic TAP1 and TAP2 genes encode a transporter protein required for delivery of cytosolic peptides to class I molecules in the endoplasmic reticulum. Associations have been observed between TAP2 alleles and predisposition to autoimmune diseases such as IDDM but their interpretation has been complicated by the existence of LD between TAP2 and HLA class II loci, and conclusions are still contradictory. In order to precisely define LD on class II haplotypes, we performed an extensive familial analysis. A total of 466 individuals from 55 normal families and 49 IDDM multiplex families was studied, providing information on 420 independent haplotypes. The IDDM-predisposing DRB1*03 and DRB1*04 alleles were in strong negative LD with TAP2-B (delta = -0.035 and -0.034, respectively), and positive LD with TAP2-A (delta = + 0.055 and + 0.012). Positive LD was also found between TAP2-B and DRB1*01 and TAP2-C and DRB1*11 alleles. We then addressed the question of whether TAP2 is an independent additional IDDM-protective or predisposing genetic factor. No TAP2 effect was evidenced when considering DRB1*03 and/or 04 patients. A decreased TAP2-B phenotype frequency was observed in DRB1*03- and DRB1*04-negative IDDM patients compared with DRB1*03- and DRB1*04-negative normal controls (38.6% vs 63%, pc < 0.05), but was probably related to a combination of different weak LD between DRB1 and TAP2 alleles. It thus appears that there is no primary association between TAP2 alleles and IDDM. However, TAP polymorphism may allow us to define particular extended HLA haplotypes involved in susceptibility to autoimmune diseases.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Molecular analysis of TCR junctional variability in individual infiltrated islets of non-obese diabetic mice: evidence for the constitution of largely autonomous T cell foci within the same pancreas.

Insulitis develops in non-obese diabetic (NOD) mice as a multicentric and asynchronous process. In an effort to understand how this T cell mediated process expands within each islet and propagates between the islets of the same pancreas, we have analyzed the junctional diversity of TCR V beta 6 and V beta 8.2 transcripts cloned from infiltrated islets. The material examined was obtained from individual islets of 8 and 12 week old NOD mice or from pooled islets of 4 week old individual mice. Compared with spleen transcripts, where every V beta 6 or V beta 8.2 clone displays a different junction, islet transcripts are considerably less diverse. Each islet harbors from one to a maximum of six independent CDR3 sequences out of 10 or more analyzed colonies. On the other hand, there is an overall diversity of sequences when comparing the islets of the same pancreas or individual mice at 4 weeks. Altogether, these results support the idea that TCR repertoires are already divergent at the very early onset of insulitis and that each islet-centered infiltrate develops rather autonomously from the oligoclonal expansion of a limited set of precursors. Recirculation between islets is limited and does not seem to be the main mode of propagation of insulitis. Finally, a close analysis of J beta usage and N additions in beta chain transcripts from infiltrating cells reveals definite biases suggestive of an ongoing selective process imposed upon intra-pancreatic T lymphocytes.

Amino Acid Sequence↗
PubMed1994

Involvement of human muscle acetylcholine receptor alpha-subunit gene (CHRNA) in susceptibility to myasthenia gravis.

The muscle acetylcholine receptor is the major target of the autoimmune response in generalized myasthenia gravis. To investigate the role of the gene encoding the alpha subunit of the receptor (CHRNA), two stable polymorphic d[(GT).(CA)]dinucleotide repeats, designated HB and BB, were characterized within the first intron of CHRNA. The HB*14 allele conferred a relative risk for myasthenia gravis of 2.5 in 81 unrelated patients compared with 100 control subjects. Very significantly, family analysis based on haplotype segregation data indicated that parental haplotypes associated with HB*14 always segregated to the child with myasthenia gravis (P < 0.0002 for the comparison with the transmission of haplotypes not bearing HB*14), whereas their transmission to unaffected siblings was equilibrated. Myasthenia gravis patients also showed a high frequency of microsatellite variants unseen in controls. These findings implicate the CHRNA in susceptibility to myasthenia gravis.

Adolescent↗
PubMed1994

The meiosis-specific Xmr gene product is homologous to the lymphocyte Xlr protein and is a component of the XY body.

The Xlr (X-chromosome linked, lymphocyte regulated) multigene family was previously found to determine, in the lymphoid cell lineage, the stage-specific expression of a nuclear protein with a primary sequence suggestive of a transcriptional activator function. We report here the characterization of a second functional member of the Xlr gene family that is abundantly transcribed in testis in a tissue-specific and developmentally regulated manner. The protein product of this newly identified gene, called Xmr (Xlr-related, meiosis regulated), is located in the nuclei of spermatocytes, early in the prophase of the first meiotic division, and later becomes concentrated in the XY nuclear subregion where it is in particular associated with the axes of sex chromosomes. The Xmr protein provides a new tool for the investigation of sex chromosome behaviour during meiosis in mammals.

Amino Acid Sequence↗
PubMed1994

Genetic analysis of immune dysfunction in non-obese diabetic (NOD) mice: mapping of a susceptibility locus close to the Bcl-2 gene correlates with increased resistance of NOD T cells to apoptosis induction.

The non-obese diabetic (NOD) mouse strain provides a remarkable model for investigating the mechanisms of autoimmunity. Independent genetic analyses of this model have previously shown that chromosome 1-linked loci were involved in the control of periinsulitis and sialitis on the one hand and of insulitis and diabetes on the other hand. In the present work, analysis of a [NOD x (NOD x C57BL/6)F1] backcross progeny allowed us to clearly dissociate two genetic regions: one was associated with periinsulitis and mapped to the middle region of chromosome 1, in the vicinity of the Bcl-2 gene; the other was associated with insulitis and mapped to the proximal part of the chromosome. Three intermediate markers D1Mit18, D1Mit5 and D1Mit19 covering at least 25 centiMorgans between these two regions, were associated with neither periinsulitis nor insulitis. The role of the Bcl-2-linked region in the immune anomalies of NOD mice was further investigated in a (NOD x C57BL/6)F2 cross where the Bcl-2nod haplotype was linked to elevated serum levels of IgG (p < 0.0005). The middle region of chromosome 1 is, therefore, involved in the control of three phenotypes, including periinsulitis, sialitis and hyperIgG, pointing to Bcl-2 as a good candidate for a cause of the NOD mouse disease. Consistent with the anti-apoptotic function of the Bcl-2 gene product, activated T lymphocytes from NOD mice showed a markedly increased resistance to induction of apoptosis following deprivation of interleukin-2 when compared to those from non-autoimmune strains. After the recent observation of the Fas gene alterations in the lpr and lprcg mutations, these findings indicate that deregulation of lymphoid cell apoptosis may be a general pathogenetic mechanism in autoimmune diseases.

Animals↗
PubMed1994

Anchored polymerase chain reaction based analysis of the V beta repertoire in the non-obese diabetic (NOD) mouse.

We have performed extensive analyses of T cell receptor V beta usage in the thymus, the spleen and the infiltrated islets of preclinical non-obese diabetic (NOD) mice. A semiquantitative anchored polymerase chain reaction (An-PCR) protocol has been developed for this purpose. The validity of the method has been first assessed by antibody staining with a panel of anti-V beta monoclonal antibodies (mAb). The results obtained by An-PCR are accurate, reproducible, and in good agreement with cell surface protein staining. A strict comparison between thymus and spleen repertoires reveals no major V beta-specific deletion except the already reported V beta 3 deletion due to Mtv-3. Certain V beta such as V beta 15, 18, 20 are found with a low frequency in the spleen, but the fact that they are also scarce in the thymus probably reflects a poor availability of these genetic elements during beta chain rearrangement rather than negative selection. Other V beta, such as V beta 2, V beta 12 and V beta 14 are significantly more abundant in the spleen than in the thymus. This finding was confirmed by mAb staining for V beta 2 and V beta 14. The expansion asymmetrically affects the CD4+ subset and can be traced back to the mature, single-positive thymocyte subset, suggesting an intrathymic positive selection event. V beta repertoires in infiltrated islets of 13- and 18-week-old, non-diabetic mice are polymorphic. Practically all the V beta found in the peripheral lymphoid tissues are present in the islets, in similar proportions. The major exception is V beta 12, one of the V beta which is subject to expansion during intrathymic differentiation and which is further augmented in the islets, both at 13 and 18 weeks. This increase probably reflects further peripheral amplification of the V beta 12-bearing subset due to encounter with the same ligand as in the thymus or with a cross-reactive motif. Finally, the nucleotide sequencing of all the V beta segments in usage in the NOD strain confirms the absence of allelic polymorphism of V beta-coding regions.

Animals↗
PubMed1994

Human IgG monoclonal autoantibodies against muscle acetylcholine receptor: direct evidence for clonal heterogeneity of the antiself humoral response in myasthenia gravis.

Human hybridomas were established from myasthenia gravis (MG) patients and screened using a fast and sensitive cell ELISA with the rhabdomyosarcoma cell line TE671. In a first series of 14 fusions using a standard protocol, 36 positive clones were detected and maintained for three passages. The number of clones in each fusion was correlated with in vivo titers of anti-acetylcholine receptor (AChR) autoantibodies. In a second series of four experiments, fusions were immediately followed by cell plating under limiting dilution conditions ('fusion cloning') providing eight stable hybridomas. These hybridomas produced monoclonal antibodies (mAbs) of IgG isotype reactive with TE671 cells, but not with AChR in solution using the radioimmunoprecipitation assay. Fine analysis of antigen specificity of these mAbs was performed using solid-phase ELISA against purified AChR from Torpedo (T-AChR) and immunoblot against recombinant chimaeric human AChR produced in bacteria. Five of the eight mAbs derived from the few patients whose antibodies showed cross-reactivity with T-AChR reacted against T-AChR. Of these five mAbs, two also reacted against chimaeric human AChR by immunoblotting. Furthermore, at least one of these two mAbs was capable of inducing antigenic modulation of labeled AChR with [125I]alpha-bungarotoxin from the surface of TE671 cells. These mAbs provide useful tools to explore the molecular basis of the structural and functional heterogeneity of the humoral anti-AChR response in myasthenia gravis.

Antibodies, Monoclonal↗