Identification of sarcoidosis susceptibility genes by association mapping and candidate gene approaches

Identification of a sarcoidosis susceptibility gene on chromosome 6 in this study has been performed using the association mapping approach.Here, a systematic three-stage single nucleotide polymorphism (SNP) scan of 16.4 Mb on chromosome 6p21 was performed in up to 947 independent cases of familial and sporadic sarcoidosis. Using TDT and case-control analyses, a 15 kb segment located at the 3-prime end of the BTNL2 gene could be identified as being strongly associated with sarcoidosis. The major disease-associated variant, rs2076530, represents a risk factor that is entirely independent of the previously reported association between sarcoidosis and alleles of the DRB1 gene, located within ~200kb of BTNL2. BTNL2 is a member of the immunoglobulin superfamily. Homology to B7-1 implicates the BTNL2 as a co-stimulatory molecule. The risk allele A of rs2076530 leads to alternative splicing of the BTNL2 transcript, which introduces a premature stop. The resulting truncated protein lacks the C-terminal IgC domain and transmembrane helix, thereby disturbing the putative co-stimulatory function of this molecule

Sequence of a complete chicken BG haplotype shows dynamic expansion and contraction of two gene lineages with particular expression patterns.

Many genes important in immunity are found as multigene families. The butyrophilin genes are members of the B7 family, playing diverse roles in co-regulation and perhaps in antigen presentation. In humans, a fixed number of butyrophilin genes are found in and around the major histocompatibility complex (MHC), and show striking association with particular autoimmune diseases. In chickens, BG genes encode homologues with somewhat different domain organisation. Only a few BG genes have been characterised, one involved in actin-myosin interaction in the intestinal brush border, and another implicated in resistance to viral diseases. We characterise all BG genes in B12 chickens, finding a multigene family organised as tandem repeats in the BG region outside the MHC, a single gene in the MHC (the BF-BL region), and another single gene on a different chromosome. There is a precise cell and tissue expression for each gene, but overall there are two kinds, those expressed by haemopoietic cells and those expressed in tissues (presumably non-haemopoietic cells), correlating with two different kinds of promoters and 5' untranslated regions (5'UTR). However, the multigene family in the BG region contains many hybrid genes, suggesting recombination and/or deletion as major evolutionary forces. We identify BG genes in the chicken whole genome shotgun sequence, as well as by comparison to other haplotypes by fibre fluorescence in situ hybridisation, confirming dynamic expansion and contraction within the BG region. Thus, the BG genes in chickens are undergoing much more rapid evolution compared to their homologues in mammals, for reasons yet to be understood.This is the final published version. It was originally published by PLOS in PLOS Genetics here: http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1004417

An In Silico Modeling Approach to Understanding the Dynamics of Sarcoidosis

BACKGROUND: Sarcoidosis is a polygenic disease with diverse phenotypic presentations characterized by an abnormal antigen-mediated Th1 type immune response. At present, progress towards understanding sarcoidosis disease mechanisms and the development of novel treatments is limited by constraints attendant to conducting human research in a rare disease in the absence of relevant animal models. We sought to develop a computational model to enhance our understanding of the pathological mechanisms of and predict potential treatments of sarcoidosis. METHODOLOGY/RESULTS: Based upon the literature, we developed a computational model of known interactions between essential immune cells (antigen-presenting macrophages, effector and regulatory T cells) and cytokine mediators (IL-2, TNFα, IFNγ) of granulomatous inflammation during sarcoidosis. The dynamics of these interactions are described by a set of ordinary differential equations. The model predicts bistable switching behavior which is consistent with normal (self-limited) and "sarcoidosis-like" (sustained) activation of the inflammatory components of the system following a single antigen challenge. By perturbing the influence of model components using inhibitors of the cytokine mediators, distinct clinically relevant disease phenotypes were represented. Finally, the model was shown to be useful for pre-clinical testing of therapies based upon molecular targets and dose-effect relationships. CONCLUSIONS/SIGNIFICANCE: Our work illustrates a dynamic computer simulation of granulomatous inflammation scenarios that is useful for the investigation of disease mechanisms and for pre-clinical therapeutic testing. In lieu of relevant in vitro or animal surrogates, our model may provide for the screening of potential therapies for specific sarcoidosis disease phenotypes in advance of expensive clinical trials

Genetic variants in mannose receptor gene (MRC1) confer susceptibility to increased risk of sarcoidosis

<p>Abstract</p> <p>Background</p> <p>Mannose receptor (MR) is a member of the C-type lectin receptor family involved in pathogen molecular-pattern recognition and thought to be critical in shaping host immune response. The aim of this study was to investigate potential associations of genetic variants in the <it>MRC1 </it>gene with sarcoidosis.</p> <p>Methods</p> <p>Nine single nucleotide polymorphisms (SNPs), encompassing the <it>MRC1 </it>gene, were genotyped in a total of 605 Japanese consisting of 181 sarcoidosis patients and 424 healthy controls.</p> <p>Results</p> <p>Suggestive evidence of association between rs691005 SNP and risk of sarcoidosis was observed independent of sex and age in a recessive model (<it>P </it>= 0.001).</p> <p>Conclusions</p> <p>These results suggest that <it>MRC1 </it>is an important candidate gene for sarcoidosis. This is the first study to imply that genetic variants in <it>MRC1</it>, a major member of the C-type lectin, contribute to the development of sarcoidosis.</p

On the Wegener granulomatosis associated region on chromosome 6p21.3

BACKGROUND: Wegener granulomatosis (WG) belongs to the heterogeneous group of systemic vasculitides. The multifactorial pathophysiology of WG is supposedly caused by yet unknown environmental influence(s) on the basis of genetic predisposition. The presence of anti-neutrophil cytoplasmic antibodies (ANCA) in the plasma of patients and genetic involvement of the human leukocyte antigen system reflect an autoimmune background of the disease. Strong associations were revealed with WG by markers located in the major histocompatibility complex class II (MHC II) region in the vicinity of human leukocyte antigen (HLA)-DPB1 and the retinoid X receptor B (RXRB) loci. In order to define the involvement of the 6p21.3 region in WG in more detail this previous population-based association study was expanded here to the respective 3.6 megabase encompassing this region on chromosome 6. The RXRB gene was analysed as well as a splice-site variation of the butyrophilin-like (BTNL2) gene which is also located within the respective region. The latter polymorphism has been evaluated here as it appears as a HLA independent susceptibility factor in another granulomatous disorder, sarcoidosis. METHODS: 150–180 German WG patients and a corresponding cohort of healthy controls (n = 100–261) were used in a two-step study. A panel of 94 microsatellites was designed for the initial step using a DNA pooling approach. Markers with significantly differing allele frequencies between patient and control pools were individually genotyped. The RXRB gene was analysed for single strand conformation polymorphisms (SSCP) and restriction fragment length polymorphisms (RFLP). The splice-site polymorphism in the BTNL2 gene was also investigated by RFLP analysis. RESULTS: A previously investigated microsatellite (#1.0.3.7, Santa Cruz genome browser (UCSC) May 2004 Freeze localisation: chr6:31257596-34999883), which was used as a positive control, remained associated throughout the whole two-step approach. Yet, no additional evidence for association of other microsatellite markers was found in the entire investigated region. Analysis of the RXRB gene located in the WG associated region revealed associations of two variations (rs10548957 p(allelic )= 0.02 and rs6531 p(allelic )= 5.20 × 10(-5), OR = 1.88). Several alleles of markers located between HLA-DPB1, SNP rs6531 and microsatellite 1.0.3.7 showed linkage disequilibrium with r(2 )values exceeding 0.10. Significant differences were not demonstrable for the sarcoidosis associated splice-site variation (rs2076530 p(allelic )= 0.80) in our WG cohort. CONCLUSION: Since a microsatellite flanking the RXRB gene and two intragenic polymorphisms are associated significantly with WG on chromosome 6p21.3, further investigations should be focussed on extensive fine-mapping in this region by densely mapping with additional markers such as SNPs. This strategy may reveal even deeper insights into the genetic contributions of the respective region for the pathogenesis of WG

Immune response CC chemokines CCL2 and CCL5 are associated with pulmonary sarcoidosis

Abstract Background Pulmonary sarcoidosis involves an intense leukocyte infiltration of the lung with the formation of non-necrotizing granulomas. CC chemokines (chemokine (C-C motif) ligand 2 (CCL2)-CCL5) are chemoattractants of mononuclear cells and act through seven transmembrane G-coupled receptors. Previous studies have demonstrated conflicting results with regard to the associations of these chemokines with sarcoidosis. In an effort to clarify previous discrepancies, we performed the largest observational study to date of CC chemokines in bronchoalveolar lavage fluid (BALF) from patients with pulmonary sarcoidosis. Results BALF chemokine levels from 72 patients affected by pulmonary sarcoidosis were analyzed by enzyme-linked immunosorbent assay (ELISA) and compared to 8 healthy volunteers. BALF CCL3 and CCL4 levels from pulmonary sarcoidosis patients were not increased compared to controls. However, CCL2 and CCL5 levels were elevated, and subgroup analysis showed higher levels of both chemokines in all stages of pulmonary sarcoidosis. CCL2, CCL5, CC chemokine receptor type 1 (CCR1), CCR2 and CCR3 were expressed from mononuclear cells forming the lung granulomas, while CCR5 was only found on mast cells. Conclusions These data suggest that CCL2 and CCL5 are important mediators in recruiting CCR1, CCR2, and CCR3 expressing mononuclear cells as well as CCR5-expressing mast cells during all stages of pulmonary sarcoidosis

Cutaneous sarcoidosis in a chronic hepatitis C patient receiving pegylated interferon and ribavirin therapy

A 61-year-old Japanese woman suffered from a small, painful, subcutaneous nodule on the sole of her foot that was 10mm across in diameter during pegylated interferon (PEG IFN) and ribavirin (RBV) combination therapy for chronic hepatitis C. Skin biopsy revealed multiple non-caseating granulomas composed of epithelioid histiocytes with multinucleate giant cells, which was consistent with sarcoidosis. Ophthalmologic examination revealed uveitis. Thoracic computed tomography (CT) showed multiple bilateral hilar lymphadenopathies and a diffuse micronodular interstitial pattern of the lungs. Genetic analysis indicated a probable homozygous haplotype of A*02:01-C*15:02-B*51:01-DRB1*16:02-DQB1*05:02 in human leukocyte antigen regions. The patient was observed carefully without any additional medication because no significant systemic symptoms were noted. Combination therapy was continued for 2months afterwards. She was asymptomatic for over 3years of follow up, and repeated hematological and biological investigations and chest CT showed improvement. In conclusion, clinicians should bear sarcoidosis in mind as a complication during PEG IFN and RBV combination therapy. They should also be aware of the usually good prognosis of PEG IFN-induced cutaneous sarcoidosis in order not to prematurely discontinue a treatment necessary for liver disease; maintenance of PEG IFN treatment may be advised with careful follow up.ArticleHEPATOLOGY RESEARCH. 43(7):801-807 (2013)journal articl

Genetic polymorphisms and susceptibility to lung disease

Susceptibility to infection by bacterium such as Bacillus anthracis has a genetic basis in mice and may also have a genetic basis in humans. In the limited human cases of inhalation anthrax, studies suggest that not all individuals exposed to anthrax spores were infected, but rather, individuals with underlying lung disease, particularly asthma, sarcoidosis and tuberculosis, might be more susceptible. In this study, we determined if polymorphisms in genes important in innate immunity are associated with increased susceptibility to infectious and non-infectious lung diseases, particularly tuberculosis and sarcoidosis, respectively, and therefore might be a risk factor for inhalation anthrax. Examination of 45 non-synonymous polymorphisms in ten genes: p47phox (NCF1), p67phox (NCF2), p40phox (NCF4), p22phox (CYBA), gp91phox (CYBB), DUOX1, DUOX2, TLR2, TLR9 and alpha 1-antitrypsin (AAT) in a cohort of 95 lung disease individuals and 95 control individuals did not show an association of these polymorphisms with increased susceptibility to lung disease

Autoimmune Disease Classification by Inverse Association with SNP Alleles

With multiple genome-wide association studies (GWAS) performed across autoimmune diseases, there is a great opportunity to study the homogeneity of genetic architectures across autoimmune disease. Previous approaches have been limited in the scope of their analysis and have failed to properly incorporate the direction of allele-specific disease associations for SNPs. In this work, we refine the notion of a genetic variation profile for a given disease to capture strength of association with multiple SNPs in an allele-specific fashion. We apply this method to compare genetic variation profiles of six autoimmune diseases: multiple sclerosis (MS), ankylosing spondylitis (AS), autoimmune thyroid disease (ATD), rheumatoid arthritis (RA), Crohn's disease (CD), and type 1 diabetes (T1D), as well as five non-autoimmune diseases. We quantify pair-wise relationships between these diseases and find two broad clusters of autoimmune disease where SNPs that make an individual susceptible to one class of autoimmune disease also protect from diseases in the other autoimmune class. We find that RA and AS form one such class, and MS and ATD another. We identify specific SNPs and genes with opposite risk profiles for these two classes. We furthermore explore individual SNPs that play an important role in defining similarities and differences between disease pairs. We present a novel, systematic, cross-platform approach to identify allele-specific relationships between disease pairs based on genetic variation as well as the individual SNPs which drive the relationships. While recognizing similarities between diseases might lead to identifying novel treatment options, detecting differences between diseases previously thought to be similar may point to key novel disease-specific genes and pathways

Childhood sarcoidosis: A rare but fascinating disorder

Childhood sarcoidosis is a rare multisystemic granulomatous disorder of unknown etiology. In the pediatric series reported from the southeastern United States, sarcoidosis had a higher incidence among African Americans. Most reported childhood cases have occurred in patients aged 13–15 years. Macrophages bearing an increased expression of major histocompatibility class (MHC) II molecules most likely initiate the inflammatory response of sarcoidosis by presenting an unidentified antigen to CD4+ Th (helper-inducer) lymphocytes. A persistent, poorly degradable antigen driven cell-mediated immune response leads to a cytokine cascade, to granuloma formation, and eventually to fibrosis. Frequently observed immunologic features include depression of cutaneous delayed-type hypersensitivity and a heightened helper T cell type 1 (Th1) immune response at sites of disease. Circulating immune complexes, along with signs of B cell hyperactivity, may also be found. The clinical presentation can vary greatly depending upon the organs involved and age of the patient. Two distinct forms of sarcoidosis exist in children. Older children usually present with a multisystem disease similar to the adult manifestations, with frequent hilar lymphadenopathy and pulmonary infiltrations. Early-onset sarcoidosis is a unique form of the disease characterized by the triad of rash, uveitis, and arthritis in children presenting before four years of age. The diagnosis of sarcoidosis is confirmed by demonstrating a typical noncaseating granuloma on a biopsy specimen. Other granulmatous diseases should be reasonably excluded. The current therapy of choice for sarcoidosis in children with multisystem involvement is oral corticosteroids. Methotrexate given orally in low doses has been effective, safe and steroid sparing in some patients. Alternative immunosuppressive agents, such as azathioprine, cyclophosphamide, chlorambucil, and cyclosporine, have been tried in adult cases of sarcoidosis with questionable efficacy. The high toxicity profile of these agents, including an increased risk of lymphoproliferative disorders and carcinomas, has limited their use to patients with severe disease refractory to other agents. Successful steroid sparing treatment with mycophenolate mofetil was described in an adolescent with renal-limited sarcoidosis complicated by renal failure. Novel treatment strategies for sarcoidosis have been developed including the use of TNF-alpha inhibitors, such as infliximab. The long-term course and prognosis is not well established in childhood sarcoidosis, but it appears to be poorer in early-onset disease