Genome-wide analysis of extended pedigrees confirms IL2-IL21 linkage and shows additional regions of interest potentially influencing coeliac disease risk.

Coeliac disease is a chronic inflammatory condition of the small intestine, triggered by dietary exposure to gluten in genetically susceptible individuals. Risk alleles at HLA-DQA1 and HLA-DQB1 are necessary for disease development, but are alone not sufficient for disease onset. We aimed to identify novel loci underlying susceptibility to coeliac disease through the use of extended Finnish and Hungarian families with multiple affected individuals. An initial whole-genome linkage approach yielded several loci that were followed up further using the Immunochip custom array. Loci with a parametric logarithm of odds (LOD) score of >1.3 were identified at 4q, 6p [human leukocyte antigen (HLA) region], 6q, 7p, 17p, 17q and at 22p. The 4q and 6q loci have been identified previously in coeliac disease risk, whereas follow-up analyses indicate that the 17p and 22p loci may be novel risk loci for coeliac disease. These loci harbour previously described risk variants for other autoimmune diseases, but their segregation patterns do not explain the linkage to coeliac disease. We followed up the linkage to the 4q region, containing the previously described interleukin (IL)2 and IL21 genes. The risk variants at 4q in the studied pedigrees are most likely distinct from previously described risk variants, indicating that the observed linkage may be due to rare high-risk variants of still unknown nature. The importance of this locus to coeliac disease risk was further shown by the finding that serum levels of IL21 were elevated in both untreated and treated coeliac patients compared to controls.

Fine mapping of the CELIAC2 locus on chromosome 5q31-q33 in the Finnish and Hungarian populations.

Celiac disease is a chronic inflammation of the small intestine, arising in genetically predisposed individuals as a result of ingestion of dietary gluten. The only confirmed and functionally characterised genetic risk factors for celiac disease are the DQ2 or DQ8 heterodimers at the major histocompatibility complex (MHC) class II locus (CELIAC1). These genes are necessary but alone not sufficient for disease onset. Genome-wide linkage scans have suggested chromosome 5q31-q33 (CELIAC2) as an important risk locus for celiac disease. This region has also been associated to other inflammatory disorders, although as yet, no clear gene associations have been found. In the current study, 11 celiac disease candidate loci were screened for genetic linkage in the Hungarian population. As the CELIAC2 locus showed the strongest evidence for linkage, this locus was selected for follow-up. Seventeen candidate genes were selected from the CELIAC2 locus, and genotyped using 48 haplotype tagging single nucleotide polymorphisms (SNPs) in large Finnish and Hungarian family materials. A subset of these, 40 tagging SNPs in 15 genes, were genotyped in an independent set of Finnish and Hungarian cases and controls. We confirmed linkage of this region with celiac disease and report strong linkage in both the Finnish and Hungarian populations. The association analysis showed modest associations throughout the whole region. These association findings were not replicated in the case-control datasets. Our study strongly supports the role of the CELIAC2 locus in celiac disease, but it also highlights the need for a more powerful study design in the region, to locate the true disease risk variants.

Linkage and association study of FcgammaR polymorphisms in celiac disease.

The Fcgamma receptor cluster on chromosome 1q23 contains a number of genes that may affect susceptibility to celiac disease, but previous studies have yielded contradictory results. We studied the FcgammaRIIa*A519G (rs1801274) and FcgammaRIIIa*A559C (rs396991) single nucleotide polymorphisms in celiac disease families from Hungary and Finland and in celiac disease case-control materials from Hungary and Italy. Neither the Hungarian nor the Italian case-control material or a meta-analysis of the combined case-control material showed significant single-marker or haplotype association. In addition, neither linkage nor family-based association tests showed evidence for association in the Finnish or Hungarian family material. This study thus does not support a previous publication showing FcgammaR association with celiac disease.

The shared CTLA4-ICOS risk locus in celiac disease, IgA deficiency and common variable immunodeficiency.

IgA deficiency (IgAD) and common variable immunodeficiency (CVID) often co-occur in families, associating with chronic inflammatory diseases such as celiac disease (CD). ICOS (inducible co-stimulator) and CTLA4 (cytotoxic T-lymphocyte-associated protein-4) may be important in both disorders, as ICOS is necessary for Ig class-switching and CTLA4 negatively regulates T-cell activation. Linkage and association of CD with CTLA4-ICOS is well documented, we thus aimed to further pinpoint CD susceptibility by haplotype-tagging analysis. We genotyped 663 CD families from Finland and Hungary, 575 additional CD patients from Finland, Hungary and Italy; 275 Swedish and Finnish IgAD individuals and 87 CVID individuals for 14-18 genetic markers in CTLA4-ICOS. Association was found between CTLA4-ICOS and both IgAD (P=0.0015) and CVID (P=0.0064). We confirmed linkage of CTLA4-ICOS with CD (LOD 2.38, P=0.0005) and found association of CTLA4-ICOS with CD (P=0.0009). Meta-analysis of the IgAD, CVID and CD materials revealed intergenic association (P=0.0005). Disease-associated markers were associated with lower ICOS and higher CTLA4 expression, indicating that the risk haplotypes contain functional variants. In summary, we identified a novel shared risk locus for IgAD, CVID and CD, the first report of association between CTLA4-ICOS and IgAD. Association between CD and CTLA4-ICOS was also confirmed in a large European data set.

Myosin IXB gene region and gluten intolerance: linkage to coeliac disease and a putative dermatitis herpetiformis association.

BACKGROUND: Coeliac disease is caused by dietary gluten, which triggers chronic inflammation of the small intestine in genetically predisposed individuals. In one quarter of the patients the disease manifests in the skin as dermatitis herpetiformis. Recently, a novel candidate gene, myosin IXB on chromosome 19p13, was shown to be associated with coeliac disease in the Dutch and Spanish populations. The same gene has previously been associated with inflammatory bowel disease, systemic lupus erythematosus and rheumatoid arthritis risk, making myosin IXB a potential shared risk factor in these inflammatory disorders. METHODS: In this study, previously reported myosin IXB variants were tested for genetic linkage and association with coeliac disease in 495 Hungarian and Finnish families and in an additional 270 patients and controls. RESULTS AND CONCLUSION: The results show significant linkage (logarithm of odds (LOD) 3.76, p = 0.00002) to 19p13 which supports the presence of a genuine risk factor for coeliac disease in this locus. Myosin IXB variants were not associated with coeliac disease in this study; however, weak evidence of association with dermatitis herpetiformis was found. The association could not explain the strong linkage seen in both phenotypes, indicating that the role of other neighbouring genes in the region cannot be excluded. Therefore, more detailed genetic and functional studies are required to characterise the role of the myosin IXB gene in both coeliac disease and dermatitis herpetiformis.

Genetic epidemiology literature in Europe: an overview.

BACKGROUND: Genetic epidemiology deals with the aetiology, distribution and control of disease in groups of relatives, and with inherited causes of disease in populations. The main goal of this overview, part of the collaborative study SPHERE (Strengthening Public Health Research in Europe) was to have an up-to-date, detailed summary of the available information for epidemiologists and researchers on the present status of genetic epidemiology in Europe. METHODS: The PubMed literature search engine was used to recruit papers published in Europe (EU15, EU + 10 and non-EU countries) in this field restricted to the time period of 1 January 1987 and 31 December 2004. RESULTS: The number of publications increased significantly in Europe in the period analysed, however, the publication activity was restricted mainly to EU15 countries, with only sporadic papers from EU + 10 countries. Research areas studied are slightly different in Europe and in the USA with a larger emphasis on cancer, mental disease and behavioural disease genetic epidemiology in Europe. CONCLUSION: The aim must be to develop research to support policy in this important field as is already seen in the United States.

Multiplex PCR assay for screening deletions in the low density lipoprotein receptor gene.

BACKGROUND: In different populations of the world, more than 150 genetic alterations of the LDL receptor gene have been identified; each of which can result in hypercholesterolaemia, but no hot spots in the gene were detected so far. Because of the existence of very variable genetic alterations in different ethnic communities, none of the assays developed for screening mutations/deletions in a population defined can be adapted to study the possible genetic defects. The present study was designed to develop a new, multiplex PCR-based, molecular biological method to screen the whole coding region of the LDL receptor gene. METHODS: Using primer pairs completely flanking the promoter and the entire exonal region, in the PCR reactions 83-386-bp long, DNA sequences were synthesised in seven different reaction mixtures. The reaction conditions of the multiplex PCR system were optimised in order to synthesise all exons and the promoter region of the gene using only two annealing temperatures. The products could be visualised separately by agarose gel electrophoresis/ethidium bromide staining. RESULTS: A rapid, effective test enabling the screening of DNA alterations in the entire LDL receptor gene was developed. Using this simple multiplex PCR assay, deletions affecting more than 10 bp in any part of the gene can be easily detected by a single agarose gel electrophoresis. CONCLUSIONS: The simplicity, specificity and versatility of the assay make it suitable system for routine screening of LDL receptor gene mutations in large population samples. This PCR assay can be recommended for screening of LDL-RG deletions in populations or groups at high risk for cardiovascular diseases.

On the mechanism of cogenotoxic action between ingested amphibole asbestos fibres and benzo[a]pyrene: I. Urinary and serum mutagenicity studies with rats.

Recently, there has been concern that ingested asbestos may cause an increase in cancer incidence in populations exposed to fibre-contaminated drinking water. Although animal experiments failed to demonstrate carcinogenicity of the oral asbestos exposure, the high adsorption capacity of the fibres creates the possibility of cocarcinogenic action with adsorbed organics. In a simple in vivo model we demonstrated earlier that UICC crocidolite and anthophyllite asbestos fibres were able to adsorb carcinogen molecules from aqueous solutions. When orally administered, these fibres increased the sister chromatid exchange frequency in bone marrow cells of rats. In the present study we tried to follow the desorption and metabolization processes of carcinogenic benzo[a]pyrene molecules transported by the ingested fibres using the highly sensitive Salmonella/Ames mutagenicity assay. The bacterial test was performed on concentrated serum and urine samples of the treated animals by using the TA98 and 100 strains in the presence and absence of liver microsomal and deconjugating enzymes. All sets of urine and serum samples failed to show mutagenic activity indicating a lack of both desorption in the serum and the ability of the liver to metabolize. Considering our results, the cytogenetic impact demonstrated earlier in the bone marrow can be explained by a local action of accumulated and transported carcinogen molecules.

Changes in superoxide anion production and phagocytosis by circulating neutrophils during tumor progression in a rat model.

The functional state of circulating neutrophils was monitored in a rat model of mesoblastic nephroma during tumor progression. Superoxide anion (O2.-) production in response to PMA and phagocytosis of yeast particles (Saccharomyces cerevisiae) were measured every second day after tumor cell implantation. Both phagocytosis and PMA-induced 02.- generation were found to be enhanced in the first period (on Days 6, 8, and 10), while they became significantly reduced in the advanced stage of cancer (on Days 12, 14, 16, and 18). The suppression of PMNL functions was accompanied with tumor progression and an increased number of neutrophils in the peripheral blood. Studies were also carried out on PMNLs isolated from normal rats and the cells were treated with plasma samples obtained from tumor-bearing animals at different stages of nephroma. Incubation of the normal cells with plasmas separated on the 2nd and 8th days of tumor growth influenced neither the 02.- generation nor the phagocytosis. In contrast, plasma preparations obtained on the 14th day significantly inhibited both 02.- production and phagocytosis by normal neutrophils. The alterations in 02'- generation and phagocytosis by PMNLs were observed in close association with tumor growth, thus they could be considered as indicators of tumor progression. However, further studies are required to see whether the granulocyte dysfunctions observed in our animal model could provide additional prognostic information in the case of human malignancies as well as to clarify the origin of inhibitory factor(s) present in the blood of tumorous animals.

Studies on genotoxicity of orally administered crocidolite asbestos in rats: implications for ingested asbestos induced carcinogenesis.

The early genotoxic action of oral exposure to UICC crocidolite asbestos fibres was studied in different short-term tests. Fischer-344 rats were gavaged with 50 mg/b.w.kg untreated asbestos fibres and fibres which had been allowed to adsorb benzo(a)pyrene molecules from extremely low concentration (0.25-2.5 microg/ml) aqueous solutions. This system can be considered a model for the drinking of potable water contaminated by asbestos fibres together with biologically active organic micro-pollutants. The Ames Salmonella mutagenicity assay was performed on concentrated urine and serum samples of treated animals. The formation of micronuclei and sister chromatid exchanges was also studied in the bone marrow of the exposed rats. The micronucleus analysis indicated marginal genotoxic activity only upon treatment with crocidolite prepared from the solution of 1 microg/ml. A dose-dependent increase was, however, demonstrated in the sister chromatid exchange frequency upon treatment with benzo(a)pyrene coated fibres. These experiments suggest the acute cogenotoxic activity of such fibres in orally exposed animals.

Genotoxicity studies on urine and bone marrow samples of rats bearing transplanted nephroma.

It was demonstrated earlier that urine of rats bearing transplanted mesoblastic nephroma had high mutagenic activity in Salmonella typhimurium, which could not be detected in serum samples of the same animals. In this paper, cytogenetic alterations are discussed and the lack of enhanced micronucleus formation in bone marrow of tumorous rats is described. The cytogenetic effect of the hydrophobic (XAD-4) urinary fraction, which has been found to be mutagenic in the TA98 Salmonella strain, was examined in CBA mice. Sister chromatid exchange (SCE) analyses were performed on bone marrow cells of animals treated with single injections of concentrated urine samples. Significant and continuous increases could be detected in the SCE frequencies caused by the urinary concentrates with development of the tumour. Pseudouridine, a suggested urinary tumour marker nucleoside, was also studied for mutagenicity in the Ames Salmonella test. Both derivatives (alpha and beta), however, failed to induce mutations in the TA98/TA100 strains, either with or without metabolic activation. In conclusion, urinary mutagen(s) produced during the renal tumour growth have a spectrum of genotoxicity involving at least two endpoints, but the high pseudouridine excretion may not be responsible for these effects.

Urinary and serum mutagenicity studies with rats bearing experimental tumours.

Urine and serum samples of rats bearing three different experimental tumours (hepatocellular carcinoma, myelomonocytic leukemia and mesoblastic nephroma) were investigated for mutagenicity with the Ames Salmonella test. Enhancement of mutagenic activity in TA98 and TA100 was observed only in the case of urine samples obtained from animals bearing nephromas. Mutagenicity increased with increasing time after implantation of tumours. There was no coincidence between urinary and serum mutagenicity under the experimental conditions employed. Further studies are needed to determine the origins, and chemical and genotoxic characteristics of urinary mutagens. In addition, the question as to whether any mutagenic substances can be detected in fractions of plasma/serum should also be experimentally addressed.