Linkage analysis of candidate genes in autoimmune thyroid disease: 1. Selected immunoregulatory genes. International Consortium for the Genetics of Autoimmune Thyroid Disease

Graves' and Hashimoto's diseases are autoimmune thyroid diseases in which the genetic contribution is complex. For this reason, identification of necessary susceptibility genes has been difficult. However, a number of immunoregulatory genes have been implicated by association studies, including: CTLA-4, a recently described protein involved in antigen presentation, located on chromosome 2q33; the T-cell receptor V alpha and V beta gene complexes, located on 14q11 and 7q35, respectively; and the Ig gene complex (IgH), located on 15q11. We used polymorphic microsatellite markers located within these genes, or gene complexes, to test for linkage (rather than association), to each of these candidates. Using markers within the loci allowed us to assume a fixed recombination fraction of 0.01 in the tested model. Three hundred eight subjects from 48 multiplex families were studied, with 142 affected subjects. Using this set of families, we have previously shown evidence of linkage with a major susceptibility locus for Graves' disease (GD-1) on 14q24.3-31, with a maximum lod (logarithm + odds) score of 2.1, at a penetrance of 80% and with a dominant mode of inheritance. In the present study, we obtained consistently negative lod scores for each of the candidate genes, assuming either dominant or recessive modes of inheritance. These data, therefore, showed evidence against linkage with all the candidate genes. Unlike association studies, linkage analyses detect major genetic influences on disease susceptibility exerted by the linked loci. The lack of linkage for the immunoregulatory genes that were studied indicated, therefore, that they were not major contributors to disease etiology.     

A new Graves disease-susceptibility locus maps to chromosome 20q11.2. International Consortium for the Genetics of Autoimmune Thyroid Disease

The autoimmune thyroid diseases (AITDs) include two related disorders, Graves disease (GD) and Hashimoto thyroiditis, in which perturbations of immune regulation result in an immune attack on the thyroid gland. The AITDs are multifactorial and develop in genetically susceptible individuals. However, the genes responsible for this susceptibility remain unknown. Recently, we initiated a whole-genome linkage study of patients with AITD, in order to identify their susceptibility genes. We studied a data set of 53 multiplex, multigenerational AITD families (323 individuals), using highly polymorphic and densely spaced microsatellite markers (intermarker distance <10 cM). Linkage analysis was performed by use of two-point and multipoint parametric methods (classic LOD-score analysis). While studying chromosome 20, we found a locus on chromosome 20q11.2 that was strongly linked to GD. A maximum two-point LOD score of 3.2 was obtained at marker D20S195, assuming a recessive mode of inheritance and a penetrance of.3. The maximum nonparametric LOD score was 2.4 (P=.00043); this score also was obtained at marker D20S195. Multipoint linkage analysis yielded a maximum LOD score of 3.5 for a 6-cM interval between markers D20S195 and D20S107. There was no evidence for heterogeneity in our sample. In our view, these results indicate strong evidence for linkage and suggest the presence of a major GD-susceptibility gene on chromosome 20q11.2.     

Genetic heterogeneity and penetrance analysis of the BRCA1 and BRCA2 genes in breast cancer families. The Breast Cancer Linkage Consortium

The contribution of BRCA1 and BRCA2 to inherited breast cancer was assessed by linkage and mutation analysis in 237 families, each with at least four cases of breast cancer, collected by the Breast Cancer Linkage Consortium. Families were included without regard to the occurrence of ovarian or other cancers. Overall, disease was linked to BRCA1 in an estimated 52% of families, to BRCA2 in 32% of families, and to neither gene in 16% (95% confidence interval [CI] 6%-28%), suggesting other predisposition genes. The majority (81%) of the breast-ovarian cancer families were due to BRCA1, with most others (14%) due to BRCA2. Conversely, the majority of families with male and female breast cancer were due to BRCA2 (76%). The largest proportion (67%) of families due to other genes was found in families with four or five cases of female breast cancer only. These estimates were not substantially affected either by changing the assumed penetrance model for BRCA1 or by including or excluding BRCA1 mutation data. Among those families with disease due to BRCA1 that were tested by one of the standard screening methods, mutations were detected in the coding sequence or splice sites in an estimated 63% (95% CI 51%-77%). The estimated sensitivity was identical for direct sequencing and other techniques. The penetrance of BRCA2 was estimated by maximizing the LOD score in BRCA2-mutation families, over all possible penetrance functions. The estimated cumulative risk of breast cancer reached 28% (95% CI 9%-44%) by age 50 years and 84% (95% CI 43%-95%) by age 70 years. The corresponding ovarian cancer risks were 0.4% (95% CI 0%-1%) by age 50 years and 27% (95% CI 0%-47%) by age 70 years. The lifetime risk of breast cancer appears similar to the risk in BRCA1 carriers, but there was some suggestion of a lower risk in BRCA2 carriers <50 years of age.     

Utility of the apolipoprotein E genotype in the diagnosis of Alzheimer's disease. Alzheimer's Disease Centers Consortium on Apolipoprotein E and Alzheimer's Disease

BACKGROUND: The epsilon4 allele of the gene encoding apolipoprotein E (APOE) is strongly associated with Alzheimer's disease, but its value in the diagnosis remains uncertain. METHODS: We reviewed clinical diagnoses and diagnoses obtained at autopsy in 2188 patients referred to 1 of 26 Alzheimer's disease centers for evaluation of dementia. The sensitivity and specificity of the clinical diagnosis or the presence of an APOE epsilon4 allele were calculated, with pathologically confirmed Alzheimer's disease used as the standard. The added value of the APOE genotype was estimated with pretest and post-test probabilities from multivariate analyses to generate receiver-operating-characteristic curves plotting sensitivity against the false positive rate. RESULTS: Of the 2188 patients, 1833 were given a clinical diagnosis of Alzheimer's disease, and the diagnosis was confirmed pathologically in 1770 patients at autopsy. Sixty-two percent of patients with clinically diagnosed Alzheimer's disease, as compared with 65 percent of those with pathologically confirmed Alzheimer's disease, had at least one APOE epsilon4 allele. The sensitivity of the clinical diagnosis was 93 percent, and the specificity was 55 percent, whereas the sensitivity and specificity of the APOE epsilon4 allele were 65 and 68 percent, respectively. The addition of information about the APOE genotype increased the overall specificity to 84 percent in patients who met the clinical criteria for Alzheimer's disease, although the sensitivity decreased. The improvement in specificity remained statistically significant in the multivariate analysis after adjustment for differences in age, clinical diagnosis, sex, and center. CONCLUSIONS: APOE genotyping does not provide sufficient sensitivity or specificity to be used alone as a diagnostic test for Alzheimer's disease, but when used in combination with clinical criteria, it improves the specificity of the diagnosis.     

Linkage analysis of HSP70 genes and historecognition locus in botryllus schlosseri

The protochordate allorecognition system has long invited comparison with the vertebrate major histocompatibility complex (MHC). In the colonial species Botryllus schlosseri, a rapid fusion or rejection response resembling graft acceptance or rejection in vertebrates is controlled by a single highly polymorphic genetic region. Because linkage between heat shock protein 70 (HSP70) genes and the MHC appears to be conserved within the vertebrate lineage, linkage relationships between two HSP70 genes (HSP70.1 and HSP70.2) and the historecognition locus (FuHC) have been analyzed in B. schlosseri. Segregation patterns of restriction fragment length polymorphisms located in the 3' flanking regions of HSP70.1 and HSP70.2 were determined for progeny of defined crosses. These progeny were also analyzed for fusibility type by an in vivo cut colony assay. No close linkage was detected between any of the three loci. These results do not support the hypothesis that the allorecognition response in B. schlosseri is determined by an MHC homologue. However, it remains a possibility that orthologues of other MHC-linked genes will be linked to the B. schlosseri FuHC.     

Evidence for a major gene for type II diabetes and linkage analyses with selected candidate genes in Mexican-Americans

We have carried out two independent family studies in low-income Mexican-Americans from San Antonio, Texas. In the first study, probands were ascertained at random without regard to any medical condition (658 examined individuals from 50 families), and in the second study, probands were subjects with type II diabetes identified in a prior epidemiological survey (523 examined individuals from 29 families). Pedigrees ranging in size from 2 to 45 family members (median 11) in the first study and from 2 to 50 family members (median 12) in the second study were examined. Diabetes was diagnosed according to World Health Organization criteria. In both sets of families, segregation analyses revealed support for a major gene with an autosomal dominant mode of inheritance influencing early age of onset of diabetes. Non-Mendelian inheritance was rejected in both data sets. Individuals with the early age of onset allele had a mean age of diabetes onset of 51 years in the first data set and 60 years in the second data set. In the first data set, the major gene accounted for approximately 70% of the phenotypic variance in age of onset of diabetes, and there were no residual family effects once the major gene effect was taken into account. In the second data set, the major gene accounted for approximately 50% of the phenotypic variance, and residual family effects were statistically significant. Linkage analyses were performed with 11 candidate genes, and tight linkage with diabetes was rejected for Rh blood group, glucose transporter 2, fatty acid-binding protein, tumor necrosis factor beta, glucokinase, and lipoprotein lipase. A logarithm of odds (LOD) score of 0.92 at a recombination fraction of 0.05 was observed for insulin receptor substrate 1. This LOD score corresponds to a chi2 of 4.24 (P = 0.039).     

From genes to public health: the applications of genetic technology in disease prevention. Genetics Working Group

OBJECTIVES: With advances in the Human Genome Project, the implications of genetic technology in disease prevention should be assessed. METHODS: The paradigm suggested in The Future of Public Health--assessment, policy development, and assurance--was used to examine the continuum from genetic technology to public health practice. RESULTS: First, important public health functions are to (1) assess the impact of genes and their interactions with modifiable disease risk factors on the health status of the population and (2) assess the impact and safety of genetic testing on the population. Second, given the many implications of genetic testing, the public health community should participate in policy development related to the timing and use of genetic testing in disease prevention. Third, whenever appropriate, the public health community needs to ensure the development of public health genetics programs (e.g. newborn screening) and evaluate the quality and effectiveness of the use of genetic testing in disease prevention. CONCLUSIONS: Although most current genetic tests are not ready for disease prevention, there is an important role for the public health community in translating genetic technology into disease prevention.     

Linkage analysis in familial Alzheimer disease: description of the Duke and Boston data sets

Familial Alzheimer diseases is a neurological disorder of adult onset. Three research centers have each contributed their families and genetic linkage data for combined analyses. The data from the Duke and Boston centers, comprising 73 pedigrees for whom numerous markers on chromosomes 19 and 21 were typed are described.     

Mutational analysis of the genes encoding the photosystem II proteins in Cyanobacterium synechocystis sp. 6803

Chlorophyll--binding protein CP43 and cytochrome b559, encoded by psbC and psbE/F genes, are the components of photosystem II (PS II). Three psbC- and four psbE/F- mutants were isolated from the collection of PS II-deficient mutants of the cyanobacterium Synechocystis sp. 6803. Restoration of photosynthetic activity was achieved by transformation of psbE/F- mutants with cloned psbE/F gene cluster from wild type cells and each of psbC- mutants--with specific part of wild type psbC gene. DNA fragments carrying the mutations were isolated from mutant cells and sequenced. The mutations which affect PS II activity were identified in psbC gene as "frameshift" mutation, stop-codon formation, or as deletion of three nucleotides resulting in loss of one of three Phe residues in position 422-424 of CP43. Sequence of mutant psbE/F genes revealed single mutations resulting in deletion of Phe-36 or substitution of Pro-63 for Leu in alpha-subunit and Val-29 for Phe in beta-subunit of cytochrome b559.     

Array-based multiplex analysis of candidate genes reveals two independent and additive genetic risk factors for myocardial infarction in the Finnish population

We analysed common variants of eight genes implicated previously as risk factors for coronary heart disease or myocardial infarction (MI) in a cross-sectional study on patients with a history of MI and in carefully matched controls from the Finnish population. The most common low density lipoprotein receptor mutations in Finland were also included in our analysis. Multiplex genotyping of the target genes was performed using a specific and efficient array-based minisequencing system. The 4G allele of the plasminogen activator inhibitor gene (P < 0.05) and the PlA2 allele of the glycoprotein IIIa gene (P < 0.01) were associated with an increased risk of MI in our study population. We analysed the combined effect of these risk alleles and found that the concurrent carrier status of the two genetic variants conferred a high risk for the development of MI in our sample (OR = 4.5, P = 0.001), which was particularly prominent in male subjects (OR = 6.4, P = 0.0005). This study demonstrates the application of a new powerful tool for genome analysis to yield information on the inherited determinants of susceptibility to MI. The observation of two separate genes contributing an additive risk of developing MI exemplifies the advantages of multiplex analysis of genetic variation.     

Linkage of LMP, TAP, and RING3 with Mhc class I rather than class II genes in the zebrafish

The LMP2 and LMP7 genes code for subunits of the proteasome, a multimeric enzymatic complex that degrades proteins into peptides. The two subunits replace corresponding constitutively expressed subunits during the immune response. Some of the peptides generated by the proteasome in the cytosol are transported by the products of the TAP1 and TAP2 genes into the lumen of the endoplasmic reticulum and are loaded onto the assembling MHC class I molecules. In mammals, the LMP2, LMP7, TAP1, and TAP2 genes reside in the class II region of the Mhc, closely linked to the RING3 gene. In the present study we identified, cloned, and sequenced the LMP, TAP2, and RING3 genes of the zebrafish, Danio rerio. We identified variants of these genes and used them in a segregation analysis of haploid embryos derived from heterozygous mothers. The analysis revealed that in zebrafish, the LMP2, LMP7, TAP12, and RING3 loci are closely linked but, in contrast to mammals, the LMP/TAP/RING3 cluster resides not in the Mhc class II but in the class I region. We also confirmed that in the zebrafish, the class I and class II regions are not linked to each other. In this species, therefore, the LMP/TAP/RING3 genes are clustered with the class I genes on a chromosome that apparently does not contain any class II genes. The linkage of LMP/TAP/RING3/class I may be the original and the LMP/TAP/RING3/class II a derived arrangement of these genes.     

Effects of age, sex, and ethnicity on the association between apolipoprotein E genotype and Alzheimer disease. A meta-analysis. APOE and Alzheimer Disease Meta Analysis Consortium

OBJECTIVE: To examine more closely the association between apolipoprotein E (APOE) genotype and Alzheimer disease (AD) by age and sex in populations of various ethnic and racial denominations. DATA SOURCES: Forty research teams contributed data on APOE genotype, sex, age at disease onset, and ethnic background for 5930 patients who met criteria for probable or definite AD and 8607 controls without dementia who were recruited from clinical, community, and brain bank sources. MAIN OUTCOME MEASURES: Odds ratios (ORs) and 95% confidence intervals (CIs) for AD, adjusted for age and study and stratified by major ethnic group (Caucasian, African American, Hispanic, and Japanese) and source, were computed for APOE genotypes epsilon2/epsilon2, epsilon2/epsilon3, epsilon2/epsilon4, epsilon3/epsilon4, and epsilon4/epsilon4 relative to the epsilon3/epsilon3 group. The influence of age and sex on the OR for each genotype was assessed using logistic regression procedures. RESULTS: Among Caucasian subjects from clinic- or autopsy-based studies, the risk of AD was significantly increased for people with genotypes epsilon2/epsilon4 (OR=2.6, 95% CI=1.6-4.0), epsilon3/epsilon4 (OR=3.2, 95% CI=2.8-3.8), and epsilon4/epsilon4 (OR=14.9, 95% CI= 10.8-20.6); whereas, the ORs were decreased for people with genotypes epsilon2/epsilon2 (OR=0.6, 95% CI=0.2-2.0) and epsilon2/epsilon3 (OR=0.6, 95% CI=0.5-0.8). The APOE epsilon4-AD association was weaker among African Americans and Hispanics, but there was significant heterogeneity in ORs among studies of African Americans (P<.03). The APOE epsilon4-AD association in Japanese subjects was stronger than in Caucasian subjects (epsilon3/epsilon4: OR=5.6, 95% CI=3.9-8.0; epsilon4/epsilon4: OR=33.1, 95% CI=13.6-80.5). The epsilon2/epsilon3 genotype appears equally protective across ethnic groups. We also found that among Caucasians, APOE genotype distributions are similar in groups of patients with AD whose diagnoses were determined clinically or by autopsy. In addition, we found that the APOE epsilon4 effect is evident at all ages between 40 and 90 years but diminishes after age 70 years and that the risk of AD associated with a given genotype varies with sex. CONCLUSIONS: The APOE epsilon4 allele represents a major risk factor for AD in all ethnic groups studied, across all ages between 40 and 90 years, and in both men and women. The association between APOE epsilon4 and AD in African Americans requires clarification, and the attenuated effect of APOE epsilon4 in Hispanics should be investigated further.     

Review of Applied Cross-cultural Psychology: Selected papers from the Second International Conference: International Association for Cross-cultural Psychology.

Reviews the book, Applied Cross-cultural Psychology: Selected papers from the Second International Conference: International Association for Cross-cultural Psychology edited by J. W. Berry adn W. J. Lonner (1975). This volume consists of a series of selected papers from the Second International Conference of the International Association for Cross-Cultural Psychology held at Queens University, Kingston, Ontario, during August 1974. The editors note that many of the conference presentations concerned applied social questions and the papers selected for the present volume were chosen to reflect and comment on applications of "social science in cultural areas where cross-cultural psychologists may be of some assistance." The book is divided into the following seven sections: Psychology and National Development, Psychology and Social Change, Cross-Cultural Orientation, Culture and Mental Health, Social Issues, Education Applications, and Comparative Approaches to the Study of Behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Linkage analysis of infantile pyloric stenosis and markers from chromosome 9q11-q33: no evidence for a major gene in this candidate region

In order to investigate useful indicators of lead contamination, 108 Japanese Black calves from a lead-contaminated farm were used. The lead concentrations in blood (Ph-B), delta-aminolevulinic acid dehydratase (ALA-D) activities, and free erythrocyte protoporphyrin (FEP) concentrations were examined. A significant negative correlation was obtained between Pb-B concentrations and ALA-D activities (r = -0.621, p < 0.01). A significant positive correlation was obtained between Ph-B concentrations and FEP concentrations (r = 0.850, p < 0.01). The calves were divided by Pb-B concentrations (micrograms/100 ml) into 5 groups (A = < or = 30, B = 31 approximately 90, C = 91 approximately 150, D = 151 approximately 210, E = > or = 211) to observe the relation of ALA-D activities, FEP concentrations and ALA-D activities in group B (r = -0.706, p < 0.05). A significant positive correlation was obtained between Pb-B concentrations and FEP concentrations in groups A, B and D (A = r = 0.496, p < 0.01; B = r = 0.686, p < 0.01; D = r = 0.529, p < 0.05). These results indicate that FEP concentrations were good indicators of lead contamination.     

A simple health control for the elderly. Screening for vitamin B12 deficiency and thyroid disease

Screening for vitamin B12 deficiency and thyroid disease is cheap and enables early diagnosis to be made and treatment to be started while it is still simple and can prevent the development of such serious conditions as dementia, depression, or irreversible tissue damage. In 1995-6, 83% (126/151) of all 75-year-olds in H?rryda, a district (population 28,500) to the east of Gothenburg, agreed to undergo a health control designed to detect hypo- or hyper-thyroidism or vitamin B12 deficiency among elderly residents without symptoms (or with atypical symptoms not easily recognised). Of the 126 participants, four (3%) had low plasma cobalamin (vitamin B12) levels (a figure similar to or lower than those reported by others), and were treated with vitamin B12 after further examination; eight (6%) had serum thyroid stimulating hormone (TSH) levels below the lower normal limit, though further examination showed all eight to be euthyroid; and two (1.6%) were diagnosed as being hypothyroid (a lower prevalence than figures reported elsewhere), and were treated with laevothyroxine. The findings suggest that such screening might be useful in primary care. However, the clinical diagnosis of vitamin B12 deficiency, and of hypo- or hyperthyroidism, is often difficult, especially in the elderly; and although a low serum TSH level is also considered to be a reliable marker of hyperthyroidism, like others this study showed that it may occur even in the absence of disease. Thus, serum TSH and plasma B12 levels are useful screening variables, but need to be complemented by other tests before diagnosis is set.     

Increased risk of autoimmune thyroid disease in hepatitis C vs hepatitis B before, during, and after discontinuing interferon therapy

BACKGROUND: Thyroid gland dysfunction has been reported to occur with variable frequency during interferon alfa (IFN-alpha) therapy in patients with the hepatitis C virus (HCV). We prospectively evaluated if the prevalence of autoimmune thyroid disease in patients with HCV differs from that in patients with the hepatitis B virus (HBV) before, at the end of, and 6 months after stopping treatment with IFN-alpha. METHODS: One hundred thirty-four patients with HCV and 41 patients with HBV were studied. Measurements of serum free thyroxine, free triiodothyronine, thyrotropin, thyroid peroxidase antibodies (TPOAbs), thyroglobulin antibodies (TgAbs), and thyrotropin-binding inhibitory immunoglobulin were performed. RESULTS: Positive levels of TPOAb and TgAb were found in 20% and 11% of patients with HCV compared with 5% and 3% of patients with HBV, respectively. At the end of IFN-alpha therapy, thyroid gland dysfunction was more prevalent in patients with HCV (12%) compared with those with HBV (3%), with thyrotropin levels significantly higher in the HCV group (P = .03). Titers of TPOAb, TgAb, and thyrotropin-binding inhibitory immunoglobulin increased significantly (P = .02, P = .04, and P = .02, respectively) at the end of IFN-alpha therapy in patients with HCV but not in those with HBV. Patients who developed thyroid gland dysfunction were predominantly female (P = .03), had decreased levels of free triiodothyronine (P<.001), and had a higher prevalence of TPOAb (P = .03) before treatment with IFN-alpha. Thyroid gland dysfunction was reversed in 60% of those with HCV 6 months after discontinuing treatment with IFN-alpha. CONCLUSIONS: Patients with HCV are more susceptible than patients with HBV to autoimmune thyroid disease. Systematic screening of thyroid gland function and TPOAb titers in all patients with HCV before, during, and after IFN-alpha therapy appears warranted. This precaution is not necessary for patients with HBV.