Anomalous behaviour of the 5' insulin gene polymorphism allele 814: lack of association with Type I diabetes in Basques. GEPV-N Group. Basque-Navarre Endocrinology and Paediatrics

A susceptibility locus (IDDM2) for Type I (insulin-dependent) diabetes mellitus has been identified as allelic variation at a variable number of tandem repeats polymorphic region upstream of the human insulin gene. In Caucasian populations, individuals homozygous for the short length alleles (26 to 63 repeats: class I) have a two- to fivefold increased risk of developing the disease, while the long alleles (more than 140 repeats: class III) are dominantly protective. Recent evidence has shown that class I alleles are not equally predisposing, and in particular, the 42-repeat allele (allele 814) can be protective when paternally inherited. We have assessed the contribution of IDDM2 to disease in a group of Basque families with Type I diabetes. As in other Caucasoid populations, we found that class I alleles, as a whole, are associated with an increased risk of developing the disease. Using a polymerase chain reaction-based assay to more accurately resolve the different sizes of individual class I alleles, we identified 14 different variants and observed that allele 814 has an anomalous behaviour in Basques, being the only class I allele that does not have an increased frequency in the diabetic alleles group. These findings provide additional support for the recently published allele-specific effects of IDDM2 in Type I diabetes pathogenesis.     

The HLA-DQ7 and -DQ8 associations in DR4-positive rheumatoid arthritis patients. A combined analysis of data available in the literature

Several different lines of evidence have demonstrated that inherited susceptibility to rheumatoid arthritis (RA) is associated with the DRB1 genes encoding the HLA-DR4 and HLA-DR1 molecules. A contrasting hypothesis has recently been proposed, suggesting that, in general, the DRB1 locus is associated with protection to RA and that the RA-associated DRB1 alleles are not responsible for the primary disease association but merely permissive for the susceptibility conferred by the HLA-DQ alleles with which they are in linkage disequilibrium. We have performed a critical review of the literature on the HLA association in RA with special emphasis on studies in which both an HLA-DR and -DQ association has been investigated. Our analyses provide strong evidence against the hypothesis that HLA-DQ molecules play a major role in the general susceptibility to RA. Thus, the strongest association in rheumatoid arthritis is with DRB1 genes rather than DQB1 genes.     

Albinism due to transposable element insertion in fish

Myelin/oligodendrocyte glycoprotein (MOG) is a major target antigen in experimental autoimmune encephalomyelitis and it has been suggested that it may as well play a key role in the demyelination process in multiple sclerosis (MS). As MOG variants could be pathogenic in autoimmune demyelinating diseases of the central nervous system, we analysed the coding sequence of MOG in MS patients and described a G-->A transition occurring in exon 3 of the human MOG gene. The mutation predicts that isoleucine substitutes for a valine at codon 145 (Val 145 Ile) in the transmembrane region of the protein. This is the first aminoacid substitution reported in human MOG. The polymorphism can be detected by restriction enzyme digestion of genomic DNA or reverse-transcribed PCR amplified products, making it a simple tool to detect a potential implication of MOG alleles in susceptibility to MS by association study. The analysis of 83 unrelated MS patients and 82 unrelated healthy controls showed that the polymorphism is found in similar proportions in MS patients (18%) and controls (14.6%). It is therefore unlikely that the MOG Val 145 Ile variant is responsible for genetic susceptibility to MS.     

Acute necrotizing encephalopathy of childhood: a novel form of acute encephalopathy prevalent in Japan and Taiwan

Molecular genotyping for the major histocompatibility complex (MHC) class II loci, HLA-DRB1, -DQB1 and -DQA1, in 100 patients with relapsing/remitting multiple sclerosis (MS) demonstrated an association with the HLA-DR2, DQw6-associated alleles DRB1*1501, DQB1*0602 and DQA1*0102, thereby extending this finding among MS patients in several countries to an Australian population. Analysis by the relative predispositional effect (RPE) method provided no evidence for a second susceptibility allele at either DQA1 or DQB1. However, our data and that of others suggest a negative association with DQA1*0101. Associations were found with DQB1 alleles sharing sequence homology with DQB1*0602, with DQB1 alleles encoding leucine at residue 26 (Leu 26), with DQA1 alleles encoding glutamine at residue 34 (Gln 34) and with Leu 26 plus Gln 34 alleles, but each was shown by two-loci linkage analysis to be secondary to the DRB1*1501, DQB1*0602, DQA1*0102 association. The recently reported negative association with DQA1 alleles encoding phenylalanine at amino acid 25, leucine at amino acid 69 and arginine at amino acid 52 was not found in this study, although there was a trend towards reduced phenylalanine at amino acid 25. The determination at a molecular level of an explanation for the world-wide association with these alleles remains elusive despite major advances in MHC typing.     

Haplotypes of the ApoA-I/C-III/A-IV gene cluster and familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is the most frequent familial lipoprotein disorder associated with premature coronary heart disease. However, no genetic defect(s) underlying FCHL has been identified. A linkage between FCHL and the apoA-I/C-III/A-IV gene cluster has been reported but not verified in other populations. A recent study identified FCHL susceptibility haplotypes at this gene cluster. To study whether such haplotypes are also associated with FCHL susceptibility in Finns, we studied 600 well-defined Finnish FCHL patients and their relatives belonging to 28 extended FCHL families by using haplotype, linkage, sib-pair, and linkage disequilibrium analyses. The genotypes of the MspI polymorphisms were associated with total serum cholesterol (P<0.01) and apoB (P<0.05) levels in spouses, which represent the general Finnish population. However, no evidence of direct involvement of any of these loci or their specific haplotypes in the expression of FCHL in the Finnish FCHL families was found.     

Role of myelin basic protein and proteolipid protein genes in multiple sclerosis: single strand conformation polymorphism analysis of the human sequences

Susceptibility to multiple sclerosis (MS) is widely held to have a strong genetic component. While the identities of genes conferring susceptibility are currently unknown, possible candidates include those genes coding for proteins which function in central nervous system (CNS) myelin. Two such genes are the human myelin basic protein (MBP) and proteolipid protein (PLP) genes, whose products make up approximately 80% of the total protein in CNS myelin. The association of a variable number tandem repeat (VNTR) 5' to the human MBP gene with MS has been the subject of conflicting reports. Here we test the hypothesis that mutations in the human MBP and PLP genes might be associated with MS by examining the entire expressed sequence of both genes by single strand conformation polymorphism (SSCP) analysis, using a panel of 71 MS patients and 71 controls. We have also re-examined the VNTR region in patients and controls. Three base changes were found in the human PLP gene and nine base changes in the human MBP gene; these were essentially equally distributed between patients and controls. No preferential distribution of various alleles of the VNTR between patients and controls was found. Although intronic and regulatory regions have not been examined, it would appear unlikely that mutations in these genes coding for the two major CNS myelin proteins contribute significantly to genetic susceptibility to MS.     

A T cell receptor beta chain variable region polymorphism associated with radiographic progression in rheumatoid arthritis

OBJECTIVE: In rheumatoid arthritis (RA) genetic factors influence susceptibility to disease and progression. Identifying these genetic factors may give more insight into the aetiology and pathogenesis of this disease. Furthermore, if these genetic markers can predict progression in an early stage of disease, timely institution of more aggressive treatment in patients with a bad prognosis may help to prevent joint damage. Several studies have shown that HLA-DRB1 alleles are associated with RA, whereas others have indicated that genes not linked to the HLA complex are also involved. Candidates for such genes are the T cell receptor (TCR) alpha/beta genes. METHODS: The association of a polymorphism in a TCR beta chain variable region gene (TCR-V beta 8) with both risk for RA and radiographic progression of joint disease was analysed after a three year follow up. A cohort of 118 white patients with a duration of disease shorter than one year at entry, and 110 white controls were typed for this (BamHI) TCR-V beta 8 polymorphism. RESULTS: The distribution of the two alleles, 2.0 and 23.0 kb, was identical in patients and controls. Radiographic progression (modified Sharp method) after a three year follow up, studied in 111 patients, was significantly less in the group possessing the 2.0 kb allele (p = 0.03). CONCLUSION: This does not confirm the reported association of the (BamHI) TCR-V beta 8 2.0 kb allele with RA. By contrast with previous findings in smaller studies, in the present study this 2.0 kb allele was protective against radiographic progression. Because well known prognostic variables in RA were corrected for, the findings indicate that the TCR-V beta 8 polymorphism studied is a new prognostic marker for this disease.     

Malignant cervical adenopathies of unknown origin

Molecular biology, gene technology and immunology have extensively clarified the aetiology and pathogenesis of insulin-dependent diabetes mellitus (IDDM). It is now obvious that the genetic background of the individual, poorly characterized environmental factors and aggressive autoimmune phenomena in a complex interplay contribute to the progression to clinical IDDM. The IDDM risk associated with certain genetic markers, e.g. the risk alleles at various HLA loci, the most strongly predisposing gene region, and the mechanisms that mediate the genetic impact may differ in different populations. In Finland the accumulated genetic evidence is so convincing that two IDDM prevention studies have been initiated. One is a population-based prediction and prevention study, while the other is conducted in first-degree relatives of IDDM patients. Both studies rely on screening of newborn infants for IDDM susceptibility alleles at the HLA-DQB1 locus. Meanwhile, in the clinical care of children with IDDM, the importance of intensified and individualized insulin therapy in prevention of diabetic microangiopathy has become increasingly clear, and should be implemented in the care of most paediatric patients.     

A systematic study of oligodendrocyte growth factors as candidates for genetic susceptibility to MS. French Multiple Sclerosis Genetics Group

OBJECTIVE: To test 23 genes coding for growth factors and their receptors as candidates for MS genetic susceptibility in 84 multiplex families of French origin by linkage analysis. BACKGROUND: Epidemiologic studies have indicated that genetic susceptibility in MS exists. To identify MS susceptibility genes, association and linkage studies were performed with candidate genes suggested by the pathology of MS. The most consistent result was genetic association and linkage of MS to human leukocyte antigen (HLA) DR15. Recent advances in the knowledge of MS pathology have suggested that the oligodendrocyte, the myelin-forming cell in the CNS, and its growth factors might play a crucial role in MS. METHODS: Fifty-two polymorphic markers within or flanking 23 candidate genes were used. Data were analyzed with the maximum likelihood score (MLS) approach. We also searched for a genetic interaction with HLA. RESULTS: Negative results were obtained for all candidate genes. The lower limits of the relative risk (Xs) possibly excluded for any candidate gene ranged from 1.3 to 2.8. Positive MLS values (up to 0.93) were observed for transforming growth factor beta 3 (TGFbeta3) in HLA DR15-associated families, suggesting a possible role for this growth factor in interaction with HLA. CONCLUSIONS: Oligodendrocyte growth factors do not play a significant role in MS genetic susceptibility, at least in the tested sample. TGFbeta3, the only gene highlighted by this study, deserves further analysis.     

Polymorphisms of dopamine receptor and transporter genes and Parkinson's disease

Disturbances of the dopamine system are involved in the pathogenesis of idiopathic Parkinson's disease (PD). Although genetic factors may play a role in the etiology of PD, there is little direct evidence implicating a specific gene. We conducted a study to test the hypothesis that allelic variations of the dopamine receptors (D2, D3, D4) and the dopamine transporter (DAT) contribute to the susceptibility to PD. Association analyses of 70 Japanese PD patients and the same number of age-matched controls did not reveal any association between alleles of the D2, D3 or D4 receptor genes or the DAT gene and PD. Thus, our results suggest that factor(s) other than allelic variations of these key proteins in the dopamine system contribute to the susceptibility to PD.     

Association of the glycogen synthase locus on 19q13 with NIDDM in Pima Indians

Skeletal muscle glycogen synthase (encoded by GYS1 on chromosome 19q13.3) is the rate-limiting enzyme in insulin-mediated non-oxidative glucose disposal. Our previous studies have demonstrated an impairment of insulin-stimulated GYS1 activities in insulin-resistant Pima Indians, and associations of non-insulin-dependent diabetes mellitus (NIDDM) with the GYS1 locus were reported recently in Finnish and Japanese populations. We have performed linkage and association analyses of GYS1 and seven additional DNA markers on 19q with NIDDM, and with parameters of insulin action in the Pima Indians. We have found a significant association of NIDDM with GYS1 genotypes (p = 0.009), and with common GYS1 alleles (p = 0.022) in the Pima Indians. We have performed a detailed comparative analysis of the GYS1 gene, mRNA, and protein product in insulin-sensitive and insulin-resistant Pima Indians. No mutations in GYS1 coding sequences were detected; nor did we find alterations of GYS1 mRNA expression or of its basal enzymatic activity in insulin-resistant Pima Indians. These results contrasted with a 25% reduction of immunoreactive protein in insulin-resistant subjects as detected by Western blotting with an antibody specific for the C-terminal end of GYS1 (t-test p = 0.024; Wilcoxon's rank-sum test, p = 0.04). Because no mutations were detected in the DNA encoding this epitope, the difference in immunoreactivity may reflect post-translational modification(s) of the protein rather than a difference in the gene itself, or it could have occurred by chance. We conclude that our data do not indicate alterations in the GYS1 gene as the cause for the observed association, and that a different locus near GYS1 may be the contributing genetic element.     

Homozygous parent affected sib pair method for detecting disease predisposing variants: application to insulin dependent diabetes mellitus

For complex genetic diseases involving incomplete penetrance, genetic heterogeneity, and multiple disease genes, it is often difficult to determine the molecular variant(s) responsible for the disease pathogenesis. Linkage and association studies may help identify genetic regions and molecular variants suspected of being directly responsible for disease predisposition or protection, but, especially for complex diseases, they are less useful for determining when a predisposing molecular variant has been identified. In this paper, we expand upon the simple concept that if a genetic factor predisposing to disease has been fully identified, then a parent homozygous for this factor should transmit either of his/her copies at random to any affected children. Closely linked markers are used to determine identity by descent values in affected sib pairs from a parent homozygous for a putative disease predisposing factor. The expected deviation of haplotype sharing from 50%, when not all haplotypes carrying this factor are in fact equally predisposing, has been algebraically determined for a single locus general disease model. Equations to determine expected sharing for multiple disease alleles or multiple disease locus models have been formulated. The recessive case is in practice limiting and therefore can be used to estimate the maximum proportion of putative susceptibility haplotypes which are in fact predisposing to disease when the mode of inheritance of a disease is unknown. This method has been applied to 27 DR3/DR3 parents and 50 DR4/DR4 parents who have at least 2 children affected with insulin dependent diabetes mellitus (IDDM). The transmission of both DR3 and DR4 haplotypes is statistically different from 50% (P < 0.05 and P < 0.001, respectively). An upper estimate for the proportion of DR3 haplotypes associated with a high IDDM susceptibility is 49%, and for DR4 haplotypes 38%. Our results show that the joint presence of non-Asp at DQ beta position 57 and Arg at DQ alpha position 52, which has been proposed as a strong IDDM predisposing factor, is insufficient to explain the HLA component of IDDM predisposition.     

Taking the pith out of reality: a reflexive methodology for psychiatric nursing research

HLA-DQ genes are the main inherited factors predisposing to IDDM. This gene region harbors long terminal repeat (DQ LTR) elements of the human endogenous retrovirus HER V-K, which we analyzed for a possible association with disease. We first investigated whether LTR segregate with DQ alleles in families. Members (n = 110) of 29 families with at least one diabetic child, unrelated patients with IDDM (n = 159), and healthy controls (n = 173) were analyzed. Genomic DNA was amplified for DQ LTR3 by a nested primer approach as well as for DQA1 and DQB1 second exons, to assign DQA1 and DQB1 alleles. DQ LTR segregated in 24 families along with DQ alleles. Of the 29 families, 20 index patients were positive for DQ LTR. The DQ LTR was in all patients on the haplotype carrying the DQA1 *0301 and DQB1 *0302 alleles. A majority of patients had DQ LTR (62%) compared with controls (38%) (p < 1.3 x 10(-5)), even after matching for the high-risk alleles DQA1 *0501, DQB1 *0201-DQA1 *0301, and DQB1 *0302 (79% of patients and 48% of controls; p < 0.02). Subtyping for DRB1 *04 alleles in all DQB1 *0302+ individuals showed 56% DRB1 *0401, DQB1 *0302 [LTR' patients vs. 29% controls with the same haplotype (p < 0.002)]. In conclusion, these data demonstrate the segregation of DQ LTR with DQA1, DQB1 alleles on HLA haplotypes. Furthermore their presence on DRB1 *0401-, DQA1 *0301-, and DQB1 *0302-positive haplotypes suggest that they contribute to DQ-related susceptibility for IDDM.     

Esophageal mucosal lesions and scleroderma: prevalence, symptoms and risk factors

There is a strong genetic influence on the susceptibility to celiac disease. Although in the vast majority of patients with celiac disease, the HLA-DQ(alpha1*0501, beta1*0201) heterodimer encoded by the alleles HLA-DQA1*0501 and HLA-DQB1*0201 seems to confer the primary disease susceptibility, it cannot be excluded that other genes contribute to disease susceptibility, as indicated by the difference in concordance rates between monozygotic twins and HLA identical siblings (70% vs. 30%). Obviously other genes involved in the genetic control of T cell mediated immune response could potentially influence susceptibility to celiac disease. The density of T cells using the gammadelta T cell receptor (TCR) is considerably increased in the jejunal epithelium of patients with celiac disease, an abnormality considered to be specific for celiac disease. This suggests an involvement of gammadelta T cells in the pathogenesis of the disease. To ascertain whether the TCR delta (TCRD) gene contributes to celiac disease susceptibility we carried out an association study and genetic linkage analysis using a highly polymorphic microsatellite marker at the TCRD locus on chromosome 14q11.2. The association study demonstrated no significant difference in allele frequencies of the TCRD gene marker between celiac disease patients and controls; accordingly, the relative risk estimates did not reach the level of statistical significance. In the linkage analysis, performed in 23 families, the logarithm of the odds (LOD) scores calculated for celiac disease versus the TCRD gene marker excluded linkage, suggesting that there is no determinant contributing to celiac disease status at or 5 cM distant to the analyzed TCRD gene marker. In conclusion, the results of the present study provide no evidence that the analyzed TCRD gene contributes substantially to celiac disease susceptibility.     

In vitro differentiation of chick spinal cord neurons in the presence of Reissner''s fibre, an ependymal brain secretion

Variation on the Y chromosome may permit our understanding the evolution of the human paternal lineage and male gene flow. This study reports upon the distribution and non random association of alleles at four Y-chromosome specific loci in four populations, three Caucasoid (Italian, Greek and Slav) and one Asian. The markers include insertion/deletion (p12f), point mutation (92R7 and pY alpha I), and repeat sequence (p21A1) polymorphisms. Our data confirm that the p12f/TaqI 8 kb allele is a Caucasoid marker and that Asians are monomorphic at three of the loci (p12f, 92R7, and pY alpha I). The alleles at 92R7 and pY alpha I were found to be in complete disequilibrium in Europeans. Y-haplotype diversity was highly significant between Asians and all three European groups (P < 0.001), but the Greeks and Italians were also significantly different with respect to some alleles and haplotypes (P < 0.02). We find strong evidence that the p12f/TaqI 8 kb allele may have arisen only once, as a deletion event, and, additionally, that the present-day frequency distribution of Y chromosomes carrying the p12f/8 kb allele suggests that it may have been spread by colonising sea-faring peoples from the Near East, possibly the Phoenicians, rather than by expansion of Neolithic farmers into continental Europe. The p12f deletion is the key marker of a unique Y chromosome, found only in Caucasians to date, labelled 'Mediterranean' and this further increases the level of Y-chromosome diversity seen among Caucasoids when compared to the other major population groups.     

Multiple sclerosis and the HLA-D region: linkage and association studies

Inheritance patterns of multiple sclerosis (MS) in multiplex families suggest a complex aetiology involving environmental and genetically determined components. The association between the HLA class II DR15, DQ6, Dw2 haplotype and MS has been well documented in patients with ancestral origins in Northern Europe. Conversely, linkage analysis of this region in multiplex families, derived from a population base, has generated negative results. Thus, given the Dw2 specificity association, evidence implicating this locus in disease susceptibility appears contradictory. We have collected and determined the HLA-DR and -DQ haplotypes of 115 sibling pairs with multiple sclerosis, and confirm a significant association with the Dw2-associated haplotype, both in index cases and their affected siblings compared with controls. However, using a sibling pair linkage analysis that restricts haplotype sharing probabilities to defined genetic models, we have not observed linkage of this region to susceptibility in MS. We discuss the basis for association and linkage and conclude that the DR15, DQ6, Dw2 haplotype does represent a susceptibility locus but its contribution to the pathogenesis is small; although it may interact epistatically with other susceptibility genes, this haplotype is not necessary for disease expression.     

Nausea and vomiting following thyroid and parathyroid surgery

The human serotonin transporter gene (hSERT) is a strong candidate for involvement in the pathogenesis of mood disorder and, using a UK Caucasian case-control sample, Collier et al found a significant association between bipolar disorder and the 12 allele of the VNTR polymorphism in intron 2 of this gene. In a European collaborative sample, Collier et al found a significant association between affective disorder and a functional deletion polymorphism in the promoter of hSERT. We have undertaken association studies using these polymorphisms in a British Caucasian sample comprising 171 DSM-IV bipolar probands, 80 DSM-IV major depression probands and 121 unrelated controls matched to bipolar probands for age, sex and ethnicity. We found no association between the promoter deletion and affective disorder but our findings with the VNTR polymorphism are similar to those of Collier and colleagues: we found a significant excess of the 12 repeat allele in bipolar probands (P = 0.031, one-tall) with a suggestion of a gene dosage effect (using genotypes bearing no 12 repeat allele as baseline, the increased risks conferred by genotypes bearing 12 repeat alleles were: heterozygote, OR = 1.24; homozygote, OR = 1.76). Our findings add to the evidence that variation at or near hSERT influences susceptibility to bipolar disorder in the British Caucasian population.