Genome-wide association study identifies HLA 8.1 ancestral haplotype alleles as major genetic risk factors for myositis phenotypes.

Autoimmune muscle diseases (myositis) comprise a group of complex phenotypes influenced by genetic and environmental factors. To identify genetic risk factors in patients of European ancestry, we conducted a genome-wide association study (GWAS) of the major myositis phenotypes in a total of 1710 cases, which included 705 adult dermatomyositis, 473 juvenile dermatomyositis, 532 polymyositis and 202 adult dermatomyositis, juvenile dermatomyositis or polymyositis patients with anti-histidyl-tRNA synthetase (anti-Jo-1) autoantibodies, and compared them with 4724 controls. Single-nucleotide polymorphisms showing strong associations (P<5×10(-8)) in GWAS were identified in the major histocompatibility complex (MHC) region for all myositis phenotypes together, as well as for the four clinical and autoantibody phenotypes studied separately. Imputation and regression analyses found that alleles comprising the human leukocyte antigen (HLA) 8.1 ancestral haplotype (AH8.1) defined essentially all the genetic risk in the phenotypes studied. Although the HLA DRB1*03:01 allele showed slightly stronger associations with adult and juvenile dermatomyositis, and HLA B*08:01 with polymyositis and anti-Jo-1 autoantibody-positive myositis, multiple alleles of AH8.1 were required for the full risk effects. Our findings establish that alleles of the AH8.1 comprise the primary genetic risk factors associated with the major myositis phenotypes in geographically diverse Caucasian populations.

Predicting cognitive ability in ageing cohorts using Type 2 diabetes genetic risk.

AIMS: To investigate whether there is overlap in the genetic determinants of Type 2 diabetes and cognitive ageing by testing whether a genetic risk score for Type 2 diabetes can predict variation in cognitive function in older people without dementia. METHODS: Type 2 diabetes genetic risk scores were estimated using various single nucleotide polymorphism significance inclusion criteria from an initial genome-wide association study, the largest in Type 2 diabetes to date. Scores were available for 2775-3057 individuals, depending on the cognitive trait. RESULTS: Type 2 diabetes genetic risk was associated with self-reported diabetes mellitus. Across varying single nucleotide polymorphism-inclusion levels, a significant association between Type 2 diabetes genetic risk and change in general cognitive function was found (median r = 0.04); however, this was such that higher Type 2 diabetes genetic risk related to higher cognitive scores. CONCLUSIONS: To investigate more fully the source of the often observed comorbidity between Type 2 diabetes and cognitive impairment, one direction for future research will be to use cognitive ability polygenic risk scores to predict Type 2 diabetes in line with the reverse causation hypothesis that people with lower pre-morbid cognitive ability are more likely to develop Type 2 diabetes.

Major histocompatibility complex diversity in the endangered Ethiopian wolf (Canis simensis).

The major histocompatibility complex (MHC) influences immune response to infection and vaccination. In most species, MHC genes are highly polymorphic, but few wild canid populations have been investigated. In Ethiopian wolves, we identified four DLA (dog leucocyte antigen)-DRB1, two DLA-DQA1 and five DQB1 alleles. Ethiopian wolves, the world's rarest canids with fewer than 500 animals worldwide, are further endangered and threatened by rabies. Major rabies outbreaks in the Bale Mountains of southern Ethiopia (where over half of the Ethiopian wolf population is located) have killed over 75% of wolves in the affected sub-populations. In 2004, following a rabies outbreak, 77 wolves were vaccinated, and 19 were subsequently recaptured to monitor the effectiveness of the intervention. Pre- and post-vaccination rabies antibody titres were available for 18 animals, and all of the animals sero-converted after vaccination. We compared the haplotype frequencies of this group of 18 with the post-vaccination antibody titre, and showed that one haplotype was associated with a lower response (uncorrected P < 0.03). In general, Ethiopian wolves probably have an adequate amount of MHC variation to ensure the survival of the species. However, we sampled only the largest Ethiopian wolf population in Bale, and did not take the smaller populations further north into consideration.

Insights into the genetic architecture of osteoarthritis from stage 1 of the arcOGEN study.

OBJECTIVES: The genetic aetiology of osteoarthritis has not yet been elucidated. To enable a well-powered genome-wide association study (GWAS) for osteoarthritis, the authors have formed the arcOGEN Consortium, a UK-wide collaborative effort aiming to scan genome-wide over 7500 osteoarthritis cases in a two-stage genome-wide association scan. Here the authors report the findings of the stage 1 interim analysis. METHODS: The authors have performed a genome-wide association scan for knee and hip osteoarthritis in 3177 cases and 4894 population-based controls from the UK. Replication of promising signals was carried out in silico in five further scans (44,449 individuals), and de novo in 14 534 independent samples, all of European descent. RESULTS: None of the association signals the authors identified reach genome-wide levels of statistical significance, therefore stressing the need for corroboration in sample sets of a larger size. Application of analytical approaches to examine the allelic architecture of disease to the stage 1 genome-wide association scan data suggests that osteoarthritis is a highly polygenic disease with multiple risk variants conferring small effects. CONCLUSIONS: Identifying loci conferring susceptibility to osteoarthritis will require large-scale sample sizes and well-defined phenotypes to minimise heterogeneity.

Assessment of the functionality of genome-wide canine SNP arrays and implications for canine disease association studies.

Domestic dogs share a wide range of important disease conditions with humans, including cancers, diabetes and epilepsy. Many of these conditions have similar or identical underlying pathologies to their human counterparts and thus dogs represent physiologically relevant natural models of human disorders. Comparative genomic approaches whereby disease genes can be identified in dog diseases and then mapped onto the human genome are now recognized as a valid method and are increasing in popularity. The majority of dog breeds have been created over the past few hundred years and, as a consequence, the dog genome is characterized by extensive linkage disequilibrium (LD), extending usually from hundreds of kilobases to several megabases within a breed, rather than tens of kilobases observed in the human genome. Genome-wide canine SNP arrays have been developed, and increasing success of using these arrays to map disease loci in dogs is emerging. No equivalent of the human HapMap currently exists for different canine breeds, and the LD structure for such breeds is far less understood than for humans. This study is a dedicated large-scale assessment of the functionalities (LD and SNP tagging performance) of canine genome-wide SNP arrays in multiple domestic dog breeds. We have used genotype data from 18 breeds as well as wolves and coyotes genotyped by the Illumina 22K canine SNP array and Affymetrix 50K canine SNP array. As expected, high tagging performance was observed with most of the breeds using both Illumina and Affymetrix arrays when multi-marker tagging was applied. In contrast, however, large differences in population structure, LD coverage and pairwise tagging performance were found between breeds, suggesting that study designs should be carefully assessed for individual breeds before undertaking genome-wide association studies (GWAS).

Risk of canine cranial cruciate ligament rupture is not associated with the major histocompatibility complex.

OBJECTIVES: To investigate the association of the major histocompatability (MHC) class II allele haplotype frequencies with the diagnosis of cranial cruciate ligament (CCL) rupture in two breeds of dog. METHODS: DNA samples from populations of Labrador Retrievers and Golden Retrievers with CCL rupture and general populations of the same breeds were characterised for three DLA class II loci (DRB1*, DQA1* and DQB1*) alleles using sequence-based typing or reference strand-mediated conformation analysis. RESULTS: Although distinct differences in haplotype types, frequencies and homozygozity were observed between the two breeds, no disease specific association could be identified for the development of the CCL rupture within either population. CLINICAL SIGNIFICANCE: The risk for developing CCL rupture was not associated with DLA haplotype group(s) in Labrador Retrievers or Golden Retrievers, thus the hypothesis that there is an autoimmune basis to CCL rupture was not supported.

CTLA4 promoter polymorphisms are associated with canine diabetes mellitus.

Canine diabetes mellitus (DM) shares many similarities with human type 1 diabetes (T1D). It is a complex genetic disorder, which shows marked differences in breed susceptibility, with Samoyed dogs being highly susceptible, whereas the Boxer breed is relatively resistant. A number of immune response genes, which have been associated with human T1D, have also been implicated in determining susceptibility to canine DM, suggesting an immune-mediated component to the disease pathogenesis. Single nucleotide polymorphisms (SNPs) in the CTLA4 gene have consistently and reproducibly been associated with human T1D and other autoimmune diseases but the canine CTLA4 gene has not previously been investigated for involvement in canine DM. SNPs of particular interest in the human association studies are those in the promoter region which affect CTLA4 expression levels, and that of exon 1 which results in a non-synonymous amino acid change. We performed a canine SNP discovery investigation of CTLA4 on a region of DNA containing exon 1 and 1.5 kb upstream sequence in order to identify promoter region SNPs. Confirmed SNPs were used in a genetic association study of a canine diabetic cohort showing that CTLA4 promoter polymorphisms were associated with diabetes in crossbreed dogs and in five Pedigree breeds-Samoyed, Miniature Schnauzer, West Highland White Terrier, Border Terrier and Labrador. Meta-analysis of these breeds showed 9 out of 15 SNPs were associated with DM and genotype and haplotype analyses also confirmed the allelic associations in these breeds.

Association of HLA-DRB1* and keloid disease in an Afro-Caribbean population.

BACKGROUND: Keloid disease (KD) is a fibroproliferative dermal tumour of unknown aetiology. The high incidence of familial clustering in KD, its prevalence in certain races and its concordance in identical twins suggest a strong genetic predisposition to keloid formation. The highest incidence of keloids is found in black populations, where the incidence has been estimated to be up to 16%. The most polymorphic genetic system in vertebrates is the major histocompatibility complex (MHC) also known as the human leucocyte antigen (HLA) system. The MHC has been shown to be strongly associated with numerous conditions. Of particular relevance is the association of DR2 with dermal fibrotic diseases including sarcoidosis and systemic sclerosis. AIMS: To investigate the aetiology of KD and the potential involvement of the MHC. METHODS: We compared the HLA-DRB1 phenotype frequencies of Afro-Caribbean patients of Jamaican origin with keloid scars against those seen in a control population of the same ethnicity (n = 121; mean age 34.8 years, range 14-88). In total, 180 keloid cases of Afro-Caribbean origin, recruited from Kingston, Jamaica, were evaluated in the study (mean age 29.7 years, range 2-90 years). HLA-DRB1 alleles were determined in all participants using a semiautomated typing system of reverse hybridization PCR with sequence-specific oligonucleotide probes. HLA-DRB1* phenotype frequencies were established in the Jamaican Afro-Caribbean population and comparisons made between cases and controls. Furthermore, the influence of multiple vs. single lesions, patient gender and family history were also investigated. RESULTS: Differences were observed between the disease and control cohorts although none was significant. CONCLUSIONS: This study does not support an association between HLA-DRB1* alleles and susceptibility to keloid in people of Afro-Caribbean origin.

Dog leucocyte antigen (DLA) class II haplotypes and risk of canine diabetes mellitus in specific dog breeds.

BACKGROUND: Canine diabetes mellitus (DM) is a common endocrine disease in domestic dogs. A number of pathological mechanisms are thought to contribute to the aetiopathogenesis of relative or absolute insulin deficiency, including immune-mediated destruction of pancreatic beta cells. DM risk varies considerably between different dog breeds, suggesting that genetic factors are involved and contribute susceptibility or protection. Associations of particular dog leucocyte antigen (DLA) class II haplotypes with DM have been identified, but investigations to date have only considered all breeds pooled together. The aim of this study was to analyse an expanded data set so as to identify breed-specific diabetes-associated DLA haplotypes. METHODS: The 12 most highly represented breeds in the UK Canine Diabetes Register were selected for study. DLA-typing data from 646 diabetic dogs and 912 breed-matched non-diabetic controls were analysed to enable breed-specific analysis of the DLA. Dogs were genotyped for allelic variation at DLA-DRB1, -DQA1, -DQB1 loci using DNA sequence-based typing. Genotypes from all three loci were combined to reveal three-locus DLA class II haplotypes, which were evaluated for statistical associations with DM. This was performed for each breed individually and for all breeds pooled together. RESULTS: Five dog breeds were identified as having one or more DLA haplotype associated with DM susceptibility or protection. Four DM-associated haplotypes were identified in the Cocker Spaniel breed, of which one haplotype was shared with Border Terriers. In the three breeds known to be at highest risk of DM included in the study (Samoyed, Tibetan Terrier and Cairn Terrier), no DLA haplotypes were found to be associated with DM. CONCLUSIONS: Novel DLA associations with DM in specific dog breeds provide further evidence that immune response genes contribute susceptibility to this disease in some cases. It is also apparent that DLA may not be contributing obvious or strong risk for DM in some breeds, including the seven breeds analysed for which no associations were identified.

Association of canine anal furunculosis with TNFA is secondary to linkage disequilibrium with DLA-DRB1*.

Anal furunculosis (AF) is a chronic inflammatory disease of perianal tissues that particularly affects German Shepherd dogs (GSD). An immune-mediated aetiopathogenesis is suggested by T-cell infiltration, upregulated cytokine gene expression, clinical response to ciclosporin therapy and a strong genetic association with the DLA-DRB1*00101 allele. Given the close proximity of TNFA and DLA-DRB1 in the canine major histocompatibility complex (MHC), together with the strong linkage disequilibrium (LD) observed across this region, the primary disease association could be with either locus. We have investigated whether there may be an association of AF with TNFA gene polymorphism in GSDs. Cohorts of AF-affected and AF-unaffected GSDs of known dog leucocyte antigen (DLA) class II profile were genotyped for 10 single nucleotide polymorphisms (SNPs) in the canine TNFA locus using Sequenom iPLEX technology. Seven discrete TNFA haplotypes were identified in GSDs for combinations of these SNPs. TNFA haplotype frequencies were compared in cases and controls. The TNFA haplotype 3 (ATCGTTACGG), was at significantly increased frequency in cases (29% vs 15%, OR 2.5, 95% CI 1.4-4.8; P = 0.003). All seven discrete TNFA SNP haplotypes were examined for their association with DLA-DRB1/DQA1/DQB1 established haplotypes. TNFA haplotype 3 was preferentially associated with both DLA-DRB1*00101(3A)- and DLA-DRB1*00102(3B)-positive haplotypes. The DLA-DRB1* 00101/TNFA-3A haplotype was significantly associated with AF (19.3% vs 5.8%; OR 3.7, 95% CI: 1.5-8.9; P = 0.003), whereas the DLA-DRB1*00102/TNFA-3B haplotype was not (P = NS). These findings suggest that susceptibility to AF in GSDs is primarily associated with DLA-DRB1*00101 and any association with the TNFA locus is secondary and is likely to be because of LD.

Clinical and human leucocyte antigen class II haplotype associations of autoantibodies to small ubiquitin-like modifier enzyme, a dermatomyositis-specific autoantigen target, in UK Caucasian adult-onset myositis.

OBJECTIVES: Autoantibodies to a novel autoantigen small ubiquitin-like modifier activating enzyme (SAE) associated with dermatomyositis (DM) have previously been identified. The aim of this study was to establish the frequency of anti-SAE autoantibodies in a UK myositis cohort and investigate clinicoimmunogenetic associations. METHODS: Clinical data and sera were studied from 266 patients recruited to the Adult Onset Myositis Immunogenetic Collaboration. Myositis sera, control sera including 250 patients with other connective tissue diseases and 50 healthy participants were screened using radio-immunoprecipitation. Immunodepletion was performed on all sera immunoprecipitating 40 and 90 kDa bands to confirm the presence of anti-SAE. DNA from 202 patients with myositis was genotyped for human leucocyte antigen (HLA)-DRB1 and DQB1; DQA1 data were inferred. RESULTS: Out of 266 patients with myositis, 11 (4%) were positive for anti-SAE, which was found exclusively in DM with a frequency of 8%. Patients with anti-SAE had a high frequency of cutaneous lesions including heliotrope (82%) and Gottron rash (82%). Of the 11, 9 (82%) had systemic features and 7 of 9 (78%) developed dysphagia. Of those nine, seven (78%) presented with skin disease before myositis onset. All patients with anti-SAE possessed at least one copy of HLA-DQB1*03. HLA-DRB1*04-DQA1*03-DQB1*03 was a significant risk factor in anti-SAE positive versus patients who were anti-SAE negative (haplotype frequency 18% vs 6%, p<0.001, OR 5.7, 95% CI 1.9 to 17.3). CONCLUSIONS: Anti-SAE is a myositis-specific autoantibody that identifies a subset of patients with adult DM. The majority of patients with anti-SAE presented with cutaneous disease and progressed to myositis with systemic features including dysphagia. This novel autoantibody has a strong association with the HLA-DRB1*04-DQA1*03-DQB1*03 haplotype.

Polymyalgia rheumatica can be distinguished from late onset rheumatoid arthritis at baseline: results of a 5-yr prospective study.

OBJECTIVE: To describe the pattern of arthropathy and HLA-DRB1 alleles associated with PMR in order to develop a diagnostic algorithm that could help distinguish PMR and RF-negative (RF -ve) late-onset RA (LO-RA) at presentation. METHODS: This was a prospective study of all patients presenting with PMR or LO-RA over a 10-yr period to one physician. Demographic, clinical and laboratory data were collected at presentation and during a minimum of 5 yrs of follow-up. The accuracy of the initial diagnosis was systematically reviewed. RESULTS: One hundred and forty-two patients with LO-RA, 147 with PMR and 42 with PMR + TA were studied. Peripheral synovitis was observed in 23% of the PMR patients. In comparison with RF -ve LO-RA, PMR patients were younger (P < 0.001), myalgia more frequent [100 vs 16% (P < 0.001)] and arthritis of PIP, MCP and wrist were less frequent (P < 0.001). The combination of wrist + MCP/PIP or wrist + PIP + MCP were highly suggestive of RF -ve LO-RA (P < 0.001). HLA-DRB1*0101/0102 and *0401 were significantly increased in PMR patients compared with healthy controls. Plasma viscosity and arthritis in the wrist, in combination with at least one MCP or PIP joint at disease onset, were predictive of whether a non-erosive RF -ve patient would ultimately be diagnosed as having RF -ve LO-RA or PMR (+/-/arthritis). CONCLUSION: Our longitudinal follow-up data were consistent with RF -ve LO-RA being a separate disease entity to PMR despite some phenotypic and immunogenetic similarities at disease onset. A diagnostic algorithm was derived using baseline clinical features to predict the final diagnosis of RF -ve, non-erosive patients.

Positive association of HLA-DRB1*15 with keloid disease in Caucasians.

Keloid disease (KD) is a fibroproliferative dermal tumour of unknown aetiology. The increased familial clustering in KD, its increased prevalence in certain races and concordance in identical twins suggest a strong genetic predisposition to keloid formation. The most polymorphic genetic system in all vertebrates is the major histocompatibility complex (MHC) also known as the human leucocyte antigens (HLA) system. The MHC has been shown to be strongly associated with numerous conditions. Of particular interest is the association of DR2 with dermal fibrotic diseases such as sarcoidosis. To investigate the aetiology of KD, we compared the HLA-DRB1 phenotype frequencies of Caucasoid patients with keloid scars against those observed in a control population (n = 537). A total number of 67 keloid cases were evaluated in the study. HLA-DRB1 alleles were determined in all cases and controls using a commercially available semiautomated reverse hybridization polymerase chain reaction sequence-specific oligonucleotide probes typing system. HLA-DRB1*15 phenotype frequency was higher in KD-positive Caucasians (38.8%) when compared with controls (20.9%) (corrected P = 0.017). We conclude that in Caucasians of Northern European origin, HLA-DRB1*15 is associated with risk of developing KD following injury. We have demonstrated for the first time that a genetic association exists between HLA-DRB1*15 status and the risk of developing keloid scarring in Caucasians. Our data suggest the possible involvement of an immunogenic component to KD although the exact mechanisms involved in MHC-driven abnormal fibrosis will require further investigation.

Canine diabetes mellitus: from phenotype to genotype.

Breed differences in susceptibility to diabetes mellitus in dogs suggest an underlying genetic component to the pathogenesis of the disease. There is little evidence for an equivalent of human type 2 diabetes in dogs, and it has been proposed that canine diabetes is more comparable to the type 1 form of the disease. Certain immune response genes, particularly those encoding major histocompatibility complex molecules involved in antigen presentation, are important in determining susceptibility to human type 1 diabetes. We tested the hypothesis that canine major histocompatibility complex genes (known as the dog leucocyte antigen) are associated with diabetes in dogs. A total of 530 diabetic dogs and more than 1000 controls were typed for dog leucocyte antigen, and associations were found with three specific haplotypes. The DLA-DRB1*009/DQA1*001/DQB1*008 haplotype shows the strongest association with diabetes in the UK dog population. This haplotype is common in diabetes-prone breeds (Samoyed, cairn terrier and Tibetan terrier) but rare in diabetes-resistant breeds (boxer, German shepherd dog and golden retriever), which could explain differences in the prevalence of diabetes in these different breeds. There is evidence that the DLA-DQA1*001 allele is also associated with hypothyroidism, suggesting that this could represent a common susceptibility allele for canine immune-mediated endocrinopathies.

HLA class II haplotype and autoantibody associations in children with juvenile dermatomyositis and juvenile dermatomyositis-scleroderma overlap.

OBJECTIVES: To investigate a large cohort of children with juvenile dermatomyositis (JDM), and those with JDM-scleroderma (JDM-SSc) overlap, using detailed serological analysis, HLA class II genotyping and clinical characterization. METHODS: Children (114) with JDM were recruited, and clinical data collected, through the JDM National Registry and Repository (UK and Ireland). Sera were assayed for ANA using standard immunofluorescence techniques and specific antibodies characterized using ELISA, immunodiffusion and radioimmunoprecipitation. Patients and controls (n = 537) were genotyped at the HLA-DRB1 and DQB1 loci, and then the DQA1 locus data was derived. RESULTS: Over 70% of the patients were ANA-positive. Clear differences in serological and genetic data were demonstrated between JDM and JDM-SSc overlap groups. Strong associations were seen for HLA-DRB1*03 (all cases vs controls, P(corr) = 0.02; JDM-SSc vs controls, P(corr) = 0.001) and HLA-DQA1*05 (all cases vs controls, P(corr) = 0.01; JDM-SSc vs controls, P(corr) = 0.005). The frequency of the HLA-DRB1*03-DQA1*05-DQB1*02 haplotype was significantly increased in the JDM-SSc (P = 0.003) and anti-PM-Scl antibody (P = 0.002) positive groups. All anti-U1-RNP antibody-positive patients had at least one copy of HLA-DRB1*04-DQA1*03-DQB1*03 haplotype. Associations were observed between serology and specific clinical features. CONCLUSIONS: We present clinical data, HLA genotyping and serological profiling on a large cohort of JDM patients and a carefully characterized subset of patients with JDM-SSc overlap. The results confirm known HLA associations and extend the knowledge by stratification of data in serological and clinical subgroups. In the future, a combination of serological and genetic typing may allow for better prediction of clinical course and disease subtype in JDM.

Lack of association between interleukin-6 promoter polymorphism at position -174 and Henoch-Schönlein pur pura.

OBJECTIVE: To assess whether polymorphism of the interleukin (IL)-6 gene at the position -174 was implicated in the incidence of Henoch-Schönlein pur-pura (HSP). A further objective was to determine if any relationship existed with severe systemic complications of HSP, in particular with severe renal and gastrointestinal involvement. METHODS: Unselected patients from Northwest Spain with primary cutaneous vasculitis classified as HSP according to proposed criteria were studied. All patients included in the present study were required to have had at least 2 year's follow-up. Patients and controls were genotyped for a single biallelic (G/C) nucleotide polymorphism in the promoter region at the position -174 of the IL-6 gene by a polymerase reaction chain-restriction fragment length polymorphism (PCR-RFLP) method. RESULTS: Forty-six Caucasian HSP patients and 124 healthy matched controls were studied. No allele or genotype differences between the whole group of HSP and controls were observed. This was also the case when HSP patients were stratified by the presence of gastrointestinal complications, nephritis, and permanent renal involvement (renal sequelae). CONCLUSION: The polymorphism in IL-6 gene promoter (-174 G/C) does not appear to be a genetic risk factor for HSP in Northwest Spain.

Endothelial nitric oxide synthase polymorphisms in biopsy-proven erythema nodosum from a defined population.

OBJECTIVE: To assess the potential in-fluence of endothelial nitric oxide synthase (eNOS) polymorphisms in the susceptibility to and clinical expression of a series of patients diagnosed with biopsy-proven erythema nodosum (EN). METHODS: Ninety-seven unselected patients from Northwest Spain with biopsy-proven EN were studied. Patients and ethnically matched controls were genotyped by PCR based techniques for a variable number tandem repeat polymorphism in intron 4, a T/C polymorphism at position -786 in the promoter region and a polymorphism in exon 7 (298Glu/Asp or 5557G/T) of the eNOS gene. RESULTS: No differences in allele or genotype frequencies for any of the individual eNOS polymorphisms were observed between biopsy-proven patients with EN and controls. It was also the case when patients with EN secondary to sarcoidosis were compared with the remaining patients or controls. In the group of patients with EN, no linkage disequilibrium between these polymorphisms was found. Also, no significant differences in haplotype frequencies were observed between patients and controls. CONCLUSION: Our present results do not support a role for eNOS polymorphisms in the susceptibility to and clinical expression of EN.

Lack of association between macrophage migration inhibitory factor gene (-173 G/C) polymorphism and cutaneous vasculitis.

OBJECTIVE: To assess whether polymorphism of the macrophage migration inhibitory factor (MIF) gene at position -173 was implicated in the incidence of Henoch-Schönlein purpura (HSP) and cutaneous leukocytoclastic angiitis (CLA). A further objective was to determine if any relationship existed with severe systemic complications of HSP, in particular with severe renal involvement and permanent renal dysfunction. METHODS: Unselected patients from Northwest Spain with primary cutaneous vasculitis classified as HSP or hypersensitivity vasculitis (HV) according to proposed criteria were studied. Patients with HV were included in this study if they fulfilled the Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitis definitions for CLA. Patients and controls were genotyped for a single nucleotide polymorphism (SNP) in the 5'-flanking region at position -173 of the MIF gene, using SNapshot ddNTP primer extension, followed by capillary electrophoresis (ABI 3100). RESULTS: Ninety-five Caucasian patients (57 classified as having HSP and 38 who fulfilled definitions for CLA) and 122 healthy controls were studied. No allele or genotype differences between the whole group of HSP or CLA patients and controls were observed. This was also the case when HSP patients were stratified by the presence of gastrointestinal complications, nephritis, and permanent renal involvement (renal sequelae). CONCLUSION: The polymorphism in MIF gene promoter (-173 G/C) does not appear to be genetic risk factors for cutaneous vasculitis in Northwest Spain.

Association of protein kinase C alpha (PRKCA) gene with multiple sclerosis in a UK population.

Twin, family and adoption studies suggest that susceptibility to multiple sclerosis is substantially mediated by genetic factors. Linkage to human chromosome 17q, homologous to a locus linked to experimental animal models of multiple sclerosis, has been widely replicated and the region likely to harbour a multiple sclerosis susceptibility gene has recently been refined to a 2.5 Mb region of 17q22-24. The candidate multiple sclerosis susceptibility gene, protein kinase C alpha (PRKCA), maps within this interval and association with 35 single-nucleotide polymorphism (SNP) markers, spanning the gene with a median spacing of 7.8 kb, was tested using a case-control approach. Single-marker genotype and estimated haplotype frequencies were compared in UK unrelated cases with multiple sclerosis (n = 184) and healthy controls (n = 340) in order to investigate association with susceptibility to disease. A haplotype of two SNPs mapping to the proximal region of the gene showed evidence for association with susceptibility (Bonferroni-corrected P value = 1.1 x 10(-5)). These findings suggest that further investigation of the PRKCA gene is warranted, particularly in cohorts with evidence of linkage to 17q22. Most of the SNPs investigated in this study were intronic and screening to identify disease-associated functional mutations is now required. Our results suggest that the promoter and proximal gene region should be not only included but prioritized in any screening strategy.

Corticotropin releasing hormone promoter polymorphisms in giant cell arteritis and polymyalgia rheumatica.

OBJECTIVE: Giant cell (temporal) arteritis (GCA) and polymyalgia rheumatica (PMR) are different but overlapping diseases of unknown etiology affecting the elderly. Corticotropin-releasing hormone (CRH) helps to regulate the immune response and maintain homeostasis during inflammatory stress. CRH promoter region polymorphisms in the 5'regulatory region of the CRH gene have been described. To investigate the possible implications of the CRH promoter polymorphisms in PMR and GCA susceptibility we have examined a series of patients with these conditions. METHODS: Sixty-two patients with biopsy-proven GCA, 86 patients with isolated PMR and 147 ethnically matched controls from the Lugo region of Northwest Spain were included in this study. Patients and controls were genotyped for CRH polymorphism in the 5' regulatory region of the gene at position 1273 (alleles A1 andA2) and at position 225 (alleles B1 and B2) by PCR-restriction fragment length polymorphism. Allele frequencies and genotype distribution were evaluated by the chi-square test. RESULTS: When GCA and PMR patients were examined for alleles and genotypes for each CRH polymorphism no significant differences in frequency were found compared with controls. A higher CRH-A2 allele frequency was observed in GCA patients with visual complications (21.4%) compared with controls (9.2%) and GCA cases without eye involvement [6.3%; p= 0.017, Pcorr = 0.034, O.R: 4.1 (95% CI 1.2- 13.9)], although this was based on a small sample of patients with ischemic visual complications (n = 14) and should be interpreted with caution. No differences in CRH allele or genotype frequencies were observed in isolated PMR patients stratified by relapses and recurrence of disease symptoms. CONCLUSION: Polymorphisms in the CRH gene regulatory region do not appear to be associated with increased susceptibility to PMR or GCA. The CRH-A2 allele may encode risk for the development of visual complications in GCA, although further studies to confirm this will be required.