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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate the genetic component of multifactorial diseases such as type 1 (insulin-dependent) diabetes mellitus (IDDM), models involving the joint action of several disease loci are important. These models can give increased power to detect an effect and a greater understanding of etiological mechanisms. Here, we present an extension of the maximum lod score method of N. Risch, which allows the simultaneous detection and modeling of two unlinked disease loci. Genetic constraints on the identical-by-descent sharing probabilities, analogous to the "triangle" restrictions in the single-locus method, are derived, and the size and power of the test statistics are investigated. The method is applied to affected-sib-pair data, and the joint effects of IDDM1 (HLA) and IDDM2 (the INS VNTR) and of IDDM1 and IDDM4 (FGF3-linked) are assessed with relation to the development of IDDM. In the presence of genetic heterogeneity, there is seen to be a significant advantage in analyzing more than one locus simultaneously. Analysis of these families indicates that the effects at IDDM1 and IDDM2 are well described by a multiplicative genetic model, while those at IDDM1 and IDDM4 follow a heterogeneity model.
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PMID:Two-locus maximum lod score analysis of a multifactorial trait: joint consideration of IDDM2 and IDDM4 with IDDM1 in type 1 diabetes. 757 54

The gene region on chromosome 11p15.5 known to be involved in insulin-dependent diabetes mellitus (IDDM) susceptibility was recently mapped to a 4.1-kilobase region including the insulin gene. The region contains 10 candidate polymorphisms that are in strong linkage disequilibrium. By genotyping 7 of these 10 polymorphisms and the tyrosine hydroxylase microsatellite in Finnish Caucasoid IDDM patients and control subjects, we demonstrate that many of the polymorphisms found to be associated with IDDM in other Caucasoid populations do not show any association in this Finnish population. Of the polymorphisms typed, only those at -23 Hph I and the variable number of tandem repeats (VNTR) sites confer significant relative risk. Furthermore, we have demonstrated that the -23 Hph I polymorphism cannot explain the association. Comparison of the genotypic patterns observed here and previously suggests that the VNTR is the most likely candidate for IDDM2. The VNTR is located adjacent to defined regulatory DNA sequences affecting insulin gene expression, which suggests a possible effect on expression of insulin or one of the neighboring genes, tyrosine hydroxylase or insulin-like growth factor 2.
Diabetes 1995 Jun
PMID:Insulin gene region-encoded susceptibility to IDDM maps upstream of the insulin gene. 778 24

We have searched the human genome for genes that predispose to type 1 (insulin-dependent) diabetes mellitus using semi-automated fluorescence-based technology and linkage analysis. In addition to IDDM1 (in the major histocompatibility complex on chromosome 6p21) and IDDM2 (in the insulin gene region on chromosome 11p15), eighteen different chromosome regions showed some positive evidence of linkage to disease. Linkages to chromosomes 11q (IDDM4) and 6q (IDDM5) were confirmed by replication, and chromosome 18 may encode a fifth disease locus. There are probably no genes with large effects aside from IDDM1. Therefore polygenic inheritance is indicated, with a major locus at the major histocompatibility complex.
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PMID:A genome-wide search for human type 1 diabetes susceptibility genes. 807 38

To date, twelve separate chromosome regions have been implicated in the development of human type 1 (insulin-dependent) diabetes mellitus. The major disease locus, IDDM1 in the major histocompatibility complex(MHC) on chromosome 6p21, accounts for about 35% of the observed familial clustering and its contribution to disease susceptibility is likely to involve polymorphic residues of class II molecules in T-cell-mediated autoimmunity. IDDM2 is encoded by a minisatellite locus embedded in the 5' regulatory region of the insulin gene. Familial clustering of disease can be explained by the sharing of alleles of at least 10 loci. IDDM1 and IDDM2 interact epistatically. For a multifactorial disease, such as type 1 diabetes, important information concerning the pathways and mechanisms involved can be gained from examining such interactions between loci, using methods that simultaneously take account of the joint effects of the various underlying genetic components.
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PMID:Multifactorial inheritance in type 1 diabetes. 853 67

Parental genomic imprinting is the phenomenon in which the behavior of a gene is modified, depending on the sex of the transmitting parent [Peterson and Sapienza (1993): Annu Rev Genet 27:7-31]. Recent observations have revealed that the inheritance patterns, age-of-onset, severity, and etiology of certain human diseases can be explained by aberrations in the establishment or the maintenance of the imprint. Examples include the Prader-Willi, Angelman, and Beckwith-Wiedemann syndromes [Nicholls (1994): Am J Hum Genet 54:733-740], malignancy [Sapienza (1990): Biochim Biophys Acta 1072:51-61; Feinberg (1993): Nat Genet 4:110-113], and insulin-dependent diabetes mellitus (IDDM) [Julier et al. (1994) Nature 354:155-159; Bennett et al. (1995) Nat Genet 9:284-292]. We review the evidence that implicates an imprinted gene in the INS-IGF2 region of chromosome 11p15 in the etiology of IDDM (referred to as the IDDM2 locus) and show that in human fetal pancreas, INS is not imprinted, thus providing an argument against INS as the candidate gene. We also examine imprinting effects on the expression of IGF2 in components of the human immune system believed to be important in IDDM and show imprinted expression in fetal thymus as early as 15 weeks gestation. We demonstrate further that in the circulating mononuclear cells of two individuals, lectin-stimulated IGF2 transcription was biallelic, indicating relaxation of imprinting, whereas in one individual, transcription was monoallelic. Finally, we review the current available data supporting a role for insulin-like growth factor-II (IGF-II) in the immune system and, more specifically, discuss the evidence supporting a role for the IGFs in the prevention of apoptosis. These data have led us to formulate a novel hypothesis that could mechanistically explain the involvement of the IDDM2 locus in the pathogenesis of IDDM.
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PMID:Imprinting of IGF2, insulin-dependent diabetes, immune function, and apoptosis: a hypothesis. 856 31

An inconsistency has come to light between the conclusion of Lucassen et al. that IDDM2 (11p15.5) must lie within a 4.1 kilobase (kb) segment at the insulin (INS) locus and their own data showing statistically significant associations between insulin-dependent diabetes mellitus (IDDM) and markers beyond the boundaries of that segment. We present data from an independent study of 201 IDDM patients and 107 non-diabetic control subjects that also show significant association with a marker 5' of the INS locus. Patients and control subjects were genotyped at INS/+ 1140 A/C (a surrogate for the variable number tandem repeat (VNTR) polymorphism in the regulatory part of the INS gene) and a marker 5' of the tyrosine hydroxylase (TH) gene, TH/pINS500-RsaI, making it 10 kb 5' of the VNTR. Homozygotes for INS/ + 1140 allele '+' were significantly more frequent among IDDM patients than among control subjects (73 vs 45%, p < 0.001) giving an odds ratio of 3.3 (95% confidence interval (CI): 2.0-5.3). A very similar association was found for homozygotes for the TH/RsaI allele '+' (53 vs 31%, p < 0.001) giving an odds ratio of 2.6 (95%CI 1.6-4.2). By multilocus analysis, the TH/RsaI allele '+' identified a subset of INS/ + 1140 alleles '+' haplotypes that are more specifically associated with IDDM (odds ratio = 5.4, 95%CI 2.9-10.4) than allele + 1140 '+' as a whole. In conclusion, the segment of chromosome 11 that is associated with IDDM spans, at least, the INS and TH loci. No legitimate claim can be made that IDDM2 corresponds to the VNTR polymorphism at the INS locus until the correct boundaries for IDDM2 have been defined and other loci within them have been excluded as determinants of IDDM.
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PMID:Diabetes susceptibility at IDDM2 cannot be positively mapped to the VNTR locus of the insulin gene. 873 20

One of the loci encoding susceptibility to insulin-dependent diabetes mellitus (IDDM) is IDDM2, mapped to a variable number of tandem repeats (VNTR) polymorphism situated 596 bp upstream of the insulin gene (INS). The shorter alleles (class I) predispose to IDDM, while the longer class III alleles are protective. Besides INS, it is possible that transcription levels of IGF2, the nearby gene encoding the insulin-like growth factor II, may be modulated by allelic forms of the VNTR. In an effort to define the pathophysiologic mechanism of the IDDM2 effect, we examined the effect, in cis, of VNTR genotype on steady-state mRNA levels of INS in samples of human fetal pancreas, and of IGF2 in leucocytes of diabetic children. Relative levels of mRNA transcripts derived from each chromosome carrying a defined VNTR allele were measured by RT-PCR, taking advantage of transcribed polymorphisms at the 3' untranslated region of each gene. In 10 samples of human fetal pancreas, INS transcripts from chromosomes carrying a class III VNTR were slightly but significantly (P = 0.015) lower than those from class I (13% lower, 95% confidence limits 3-21%). In 10 leucocyte samples, mRNA from both IGF2 alleles was seen, indicating relaxation of the parental imprinting of IGF2 in these cells. However, this relaxation was incomplete as maternal allele mRNA was systematically at a lower level than paternal. The paternal/maternal ratio varied widely among individual subjects. Two of the most extreme cases, demonstrating almost complete repression of the maternal allele, were identical twins, suggesting that this variable relaxation of imprinting is genotype-dependent. However, this genotype-dependence cannot be accounted for by the maternal VNTR, as the mean ratios of paternal/maternal IGF2 mRNA levels were not statistically different in individuals with a maternal VNTR of class I vs. class III (3.2 +/- 1.5 vs. 3.89 +/- 0.94). Thus, we present evidence that: (a) class III VNTR alleles are associated with lower INS mRNA in fetal pancreas than class I alleles. The biologic importance of this difference remains to be determined; and (b) the variable relaxation of IGF2 imprinting seen in human leucocytes is not dependent on the presence of a class I vs. a class III VNTR.
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PMID:Imprinted and genotype-specific expression of genes at the IDDM2 locus in pancreas and leucocytes. 881 77

Susceptibility to autoimmune insulin-dependent (type 1) diabetes mellitus is determined by a combination of environmental and genetic factors, which include variation in MHC genes on chromosome 6p21 (IDDM1) and the insulin gene on chromosome 11p15 (IDDM2). However, linkage to IDDM1 and IDDM2 cannot explain the clustering of type 1 diabetes in families, and a role for other genes is inferred. In the present report we describe linkage and association of type 1 diabetes to the CTLA-4 gene (cytotoxic T lymphocyte associated-4) on chromosome 2q33 (designated IDDM12). CTLA-4 is a strong candidate gene for T cell-mediated autoimmune disease because it encodes a T cell receptor that mediates T cell apoptosis and is a vital negative regulator of T cell activation. In addition, we provide supporting evidence that CTLA-4 is associated with susceptibility to Graves' disease, another organ-specific autoimmune disease.
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PMID:The CTLA-4 gene region of chromosome 2q33 is linked to, and associated with, type 1 diabetes. Belgian Diabetes Registry. 881 51

Whereas it is well known that the insulin gene (INS) region at 11p15.5 (IDDM2) confers susceptibility to insulin-dependent diabetes mellitus (IDDM), it is still controversial whether the parental origin of IDDM2 influences IDDM susceptibility. We have analysed the Pst I + 1127 polymorphism in 123 USA multiplex families and detected linkage only in male meioses using the affected sibpair analysis (P = 0.009). Application of the transmission/disequilibrium test (TDT) found significantly increased transmission of the IDDM-associated INS allele from fathers heterozygous for INS to their diabetic offspring (P = 0.00002), but the transmission from heterozygous mothers was not significantly different from random expectation. In non-diabetic families, the transmission from parents heterozygous for INS was not significantly different from random expectation in either paternal or maternal meioses. Maternal imprinting of the INS gene in pancreatic islets was originally considered the most favorable explanation for the observed gender-related difference. However, our study has demonstrated biallelic expression of INS in pancreatic tissues from the human fetuses and thus suggests that INS is probably not imprinted in the pancreatic islets.
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PMID:Paternally transmitted IDDM2 influences diabetes susceptibility despite biallelic expression of the insulin gene in human pancreas. 884 59

Two large population-based case-control studies are reviewed. The aim is to determine the effects of HLA, other genetic factors and immune markers (ICA, IAA and GAD65Ab) on the age at onset of insulin-dependent diabetes mellitus (IDDM) in 0-34 year olds. The primary HLA risk gene sequence for IDDM was difficult to identify because of the low recombination frequency within the HLA region. The frequency of the DR3-DQA1*0501-DQB1*0201 haplotype and the DR3-DQA1*0501-DQB1*0201 (DQ2)/DR4-DQA1*0301-DQB1*0302 (DQ8) genotype were higher among patients diagnosed before the age of 10 compared with those diagnosed after the age of 30. The negatively associated haplotype, DR15-DQA1*0102-DQB1*0602 was absent before the age of 10, but the frequency increased with increasing age at onset. The IDDM2 gene representing the variable number of tandem repeat (VNTR) sequences and 5' of the insulin gene on chromosome 11 were associated with IDDM since homozygous short VNTR was positive but not homozygous, and heterozygous long VNTR was negatively associated with the disease. The diagnostic sensitivity and specificity of GAD65 (GA65Ab) and insulin (IAA) autoantibodies varied with the age at onset and gender. GAD65Ab had the highest sensitivity (> 80%) in patients older than 20 years of age with no difference in gender. The lowest sensitivity (54%) was in 0-10 year old boys, while age did not affect the sensitivity in girls. In contrast, the sensitivity of IAA was highest (46%) before the age of 15 but decreased thereafter as did the sensitivity for ICA. Classification of patients who develop IDDM above 20-25 years of age was inadequate since many patients classified with NIDDM either had GAD65Ab or ICA or developed these antibodies after 1-2 years of NIDDM. We conclude that not only age but also gender affect the risk for IDDM associated with HLA, other IDDM genes as well as commonly used immunological markers for IDDM.
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PMID:Genetic and immunological findings in patients with newly diagnosed insulin-dependent diabetes mellitus. The Swedish Childhood Diabetes Study Group and The Diabetes Incidence in Sweden Study (DISS) Group. 885 82


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