Manfred Schürmann

Sarcoidosis is associated with a truncating splice site mutation in BTNL2.

Sarcoidosis is a polygenic immune disorder with predominant manifestation in the lung. Genome-wide linkage analysis previously indicated that the extended major histocompatibility locus on chromosome 6p was linked to susceptibility to sarcoidosis. Here, we carried out a systematic three-stage SNP scan of 16.4 Mb on chromosome 6p21 in as many as 947 independent cases of familial and sporadic sarcoidosis and found that a 15-kb segment of the gene butyrophilin-like 2 (BTNL2) was associated with the disease. The primary disease-associated variant (rs2076530; PTDT = 3 × 10−6, Pcase-control = 1.1 × 10−8; replication PTDT = 0.0018, Pcase-control = 1.8 × 10−6) represents a risk factor that is independent of variation in HLA-DRB1. BTNL2 is a member of the immunoglobulin superfamily and has been implicated as a costimulatory molecule involved in T-cell activation on the basis of its homology to B7-1. The G → A transition constituting rs2076530 leads to the use of a cryptic splice site located 4 bp upstream of the affected wild-type donor site. Transcripts of the risk-associated allele have a premature stop in the spliced mRNA. The resulting protein lacks the C-terminal IgC domain and transmembrane helix, thereby disrupting the membrane localization of the protein, as shown in experiments using green fluorescent protein and V5 fusion proteins.

Eye tracking dysfunction is a putative phenotypic susceptibility marker of schizophrenia and maps to a locus on chromosome 6p in families with multiple occurrence of the disease

The difficulties in defining the borders of the schizophrenia spectrum is one major source of variance in linkage studies of schizophrenia. The employment of biological markers may prove advantageous. Due to empirical evidence, eye tracking dysfunction (ETD) has been discussed to be the most promising marker for genetic liability to schizophrenia. With respect to the recent progress in genomic scans, which have pointed to the short arm of chromosome 6, we carried out a scan of the 6p21-23 region with 16 microsatellite markers to test for linkage between chromosomal markers and ETD as well as schizophrenia. We tested 5 models of inheritance of ETD and found maximum two-point lod scores of 3.51 for D6S271 and 3.44 for D6S282. By including these markers in a multipoint analysis, a lod score of 4.02 was obtained. In the case of schizophrenia, 7 models were tested; however, with non-significant results. Our findings, together with another recent linkage report, point to the possibility of a second susceptibility locus for schizophrenia which may be located centromeric to the HLA region. Also, the evidence of ETD being a susceptibility marker for schizophrenia receives further support.

CARD15 gene mutations in sarcoidosis

Sarcoidosis, Blau syndrome and Crohns disease are complex disorders, characterised by granulomatous inflammation affecting a variety of organs. Mutations of the CARD15 gene, on chromosome 16, have been shown to contribute significantly to Crohns disease and to cause Blau syndrome. These factors prompted the current authors to study CARD15 mutations in sarcoidosis. A total of 138 families were genotyped, including 302 patients with sarcoidosis and 127 patients without a family history of sarcoidosis (together with their parents), for four main coding CARD15 polymorphisms associated with increased risk of Crohns disease. Furthermore, the gene segment that harbours Blau syndrome mutations was sequenced in 39 selected patients from 39 families with affected siblings identical for one or two parental chromosomes 16s and in eight patients from multi-case families. None of the reported Blau syndrome mutations and no new sequence alterations were found. There was an increased frequency of transmission of the rare allele of the polymorphic sites 802C>T (SNP5) and 2722G>C (SNP12) in at least one of the two study groups. In conclusion, CARD15 mutations, which are important in Crohns disease and Blau syndrome, play no major role in sarcoidosis in this study population. However, these mutations could be of limited importance, especially in patients without a family history of sarcoidosis.

Genome-Wide Association Analysis in Sarcoidosis and Crohn's Disease Unravels a Common Susceptibility Locus on 10p12.2

BACKGROUND & AIMS Crohns disease (CD) and sarcoidosis (SA) are chronic inflammatory barrier diseases that share several clinical and immunological features, including the occurrence of granulomas. METHODS A 100k genome-wide association study with 83,360 single-nucleotide polymorphisms (SNPs) was performed on 382 CD patients, 398 SA patients, and 394 control individuals. The 24 SNPs that were most strongly associated in the combined CD/SA phenotype were selected for verification in an independent sample of 1,317 patients (660 CD and 657 SA) and 1,091 controls. RESULTS The most significant association (Bonferroni corrected P = .036) was obtained at SNP rs1398024 on chromosome 10p12.2, with an odds ratio (OR) for both diseases of 0.81 (95% confidence interval [CI], 0.69-0.96) for carriership of the rarer allele A. The P value in the overall combined sample was 4.24 x 10(-6). During further follow-up, a moderate association (OR, 0.83; 95% CI, 0.72-0.96; P = .015) was observed between rs1398024 and ulcerative colitis (1,080 patients vs 1,091 controls), the second main subphenotype of inflammatory bowel disease in addition to CD. Extensive fine mapping of the 10p12.2 locus points to yet unidentified variants in the C10ORF67 gene region as the most likely underlying risk factors. CONCLUSION Our study demonstrates that the combined analysis of different, albeit clinically related, phenotypes can lead to the identification of common susceptibility loci.

Genetics of Sarcoidosis

Sarcoidosis is a multigenic and multifactorial disease. Predisposing genes have been identified and fast progress in molecular technologies including systematic genome-wide association studies and large-scale resequencing will aid the discovery of further risk loci and variants. The exploration of the molecular epidemiology of genetic variants in the pathogenesis of sarcoidosis will allow an assessment of their prognostic usefulness. To this end, different granulomatous disorders of known and unknown etiology should be investigated jointly by genetic, immunobiological, and proteomic approaches. The definition of individual genetic risk profiles in sarcoidosis and other chronic inflammatory disorders seems achievable and a useful route for clinical translation.

Gene polymorphisms of immunoregulatory cytokines and angiotensin-converting enzyme in Wegener's granulomatosis

Wegeners granulomatosis is a granulomatous and vasculitic disease of unknown origin. Gene polymorphisms are known to affect phenotypes of numerous diseases. Polymorphisms within the angiotensin-converting enzyme (ACE), transforming growth factor-β1 (TGF-β1), and interleukin-10 (IL-10) genes are suspected to modify the course of granulomatous disorders. We examined whether the genotype frequencies of the named polymorphisms differ in Wegeners granulomatosis from those in healthy controls. Thirty-nine patients with Wegeners granulomatosis were genotyped for the deletion/insertion polymorphism in intron 16 of the ACE gene, a biallelic polymorphism in codon 25 of the TGF-β1 gene and a biallelic polymorphism at position –1082 of the IL-10 gene and compared with healthy blood donors. For the ACE polymorphism no significant differences were detected neither in the allele frequencies nor in the genotype frequencies. For TGF-β1 a trend to genotype CG was found. The most interesting result was the observed, significant shift to genotype AA of the IL-10 polymorphism in Wegeners granulomatosis. IL-10 and TGF-β1, immunoregulatory cytokines capable of down-regulating T helper cell type 1 response, showed a significant shift or a trend, respectively towards genotypes associated with reduced cytokine release, leading to the hypothesis that different immunoregulatory cytokine patterns dependent on gene polymorphisms might be involved in the pathogenesis of Wegeners granulomatosis.

Angiotensin-converting enzyme (ACE) gene polymorphisms and familial occurrence of sarcoidosis

Abstract. Schürmann M, Reichel P, Müller‐Myhsok B, Dieringer T, Wurm K, Schlaak M, Müller‐Quernheim J, Schwinger E (Medical University Lübeck; Bernhard Nocht Institute, Hamburg; St. Georgs Hospital, Höchenschwand; and Medical Hospital, Research Center Borstel, Germany). Angiotensin‐converting enzyme (ACE) gene polymorphisms and familial occurrence of sarcoidosis. J Intern Med 2001; 249: 77–83.

Testing for linkage of eye tracking dysfunction and schizophrenia to markers on chromosomes 6, 8, 9, 20, and 22 in families multiply affected with schizophrenia

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A genome-wide association study reveals evidence of association with sarcoidosis at 6p12.1

Sarcoidosis is a complex systemic inflammatory disease of unknown aetiology that is influenced by a variety of genetic and environmental factors. To identify further susceptibility loci for sarcoidosis, a genome-wide association study (GWAS) was conducted in 381 patients and 392 control individuals based on Affymetrix 100k GeneChip data. The top 25 single-nucleotide polymorphisms (SNPs) were selected for validation in an independent study panel (1,582 patients versus 1,783 controls). Variant rs10484410 on chromosome 6p12.1 was significantly associated, with a Bonferroni-corrected p-value of 2.90×10−2 in the validation sample and a nominal p-value of 2.64×10−4 in the GWAS. Extensive fine mapping of the novel locus narrowed down the signal to a region comprising the genes BAG2, C6orf65, KIAA1586, ZNF451 and RAB23. Verification of the sarcoidosis-associated nonsynonymous SNP rs1040461 in a further independent case–control sample and quantitative mRNA expression studies point to the RAB23 gene as the most likely risk factor. RAB23 is proposed to be involved in antibacterial defence processes and regulation of the sonic hedgehog signalling pathway. The identified association of the 6p12.1 locus with sarcoidosis implicates this locus as a further susceptibility factor and RAB23 as a potential signalling component that may open up new perspectives in the pathophysiology of sarcoidosis.

Identification of Immune-Relevant Factors Conferring Sarcoidosis Genetic Risk

RATIONALE Genetic variation plays a significant role in the etiology of sarcoidosis. However, only a small fraction of its heritability has been explained so far. OBJECTIVES To define further genetic risk loci for sarcoidosis, we used the Immunochip for a candidate gene association study of immune-associated loci. METHODS Altogether the study population comprised over 19,000 individuals. In a two-stage design, 1,726 German sarcoidosis cases and 5,482 control subjects were genotyped for 128,705 single-nucleotide polymorphisms using the Illumina Immunochip for the screening step. The remaining 3,955 cases, 7,514 control subjects, and 684 parents of affected offspring were used for validation and replication of 44 candidate and two established risk single-nucleotide polymorphisms. MEASUREMENTS AND MAIN RESULTS Four novel susceptibility loci were identified with genome-wide significance in the European case-control populations, located on chromosomes 12q24.12 (rs653178; ATXN2/SH2B3), 5q33.3 (rs4921492; IL12B), 4q24 (rs223498; MANBA/NFKB1), and 2q33.2 (rs6748088; FAM117B). We further defined three independent association signals in the HLA region with genome-wide significance, peaking in the BTNL2 promoter region (rs5007259), at HLA-B (rs4143332/HLA-B*0801) and at HLA-DPB1 (rs9277542), and found another novel independent signal near IL23R (rs12069782) on chromosome 1p31.3. CONCLUSIONS Functional predictions and protein network analyses suggest a prominent role of the drug-targetable IL23/Th17 signaling pathway in the genetic etiology of sarcoidosis. Our findings reveal a substantial genetic overlap of sarcoidosis with diverse immune-mediated inflammatory disorders, which could be of relevance for the clinical application of modern therapeutics.