STAT1 deficiency underlies a proinflammatory imprint of naive CD4+ T cells in spondyloarthritis.

Introduction: In spondyloarthritis (SpA), an increased type 3 immune response, including T helper cells (Th) 17 excess, is observed in both human and SpA animal models, such as the HLA-B27/human ß2-microglobulin transgenic rat (B27-rat). Methods: To investigate this unexplained Th17-biased differentiation, we focused on understanding the immunobiology of B27-rat naive CD4+ T cells (Tn). Results: We observed that neutrally stimulated B27-rat Tn developed heightened Th17 profile even before disease onset, suggesting an intrinsic proinflammatory predisposition. In parallel with this observation, transcriptomic and epigenomic analyses showed that B27-rat Tn exhibited a decreased expression of Interferon/Th1- and increased expression of Th17-related genes. This molecular signature was predicted to be related to an imbalance of STAT1/STAT3 transcription factors activity. Stat1 mRNA and STAT1 protein expression were decreased before disease onset in Tn, even in their thymic precursors, whereas Stat3/STAT3 expression increased upon disease establishment. Confirming the relevance of these results, STAT1 mRNA expression was also decreased in Tn from SpA patients, as compared with healthy controls and rheumatoid arthritis patients. Finally, stimulation of B27-rat Tn with a selective STAT1 activator abolished this preferential IL-17A expression, suggesting that STAT1-altered activity in B27-rats allows Th17 differentiation. Discussion: Altogether, B27-rat Tn harbor a STAT1 deficiency preceding disease onset, which may occur during their thymic differentiation, secondarily associated with a persistent Th17 bias, which is imprinted at the epigenomic level. This early molecular phenomenon might lead to the persistent proinflammatory skew of CD4+ T cells in SpA patients, thus offering new clues to better understand and treat SpA.

Both Disease Activity and HLA-B27 Status Are Associated With Gut Microbiome Dysbiosis in Spondyloarthritis Patients.

OBJECTIVE: Gut microbiome dysbiosis has previously been reported in spondyloarthritis (SpA) patients and could be critically involved in the pathogenesis of this disorder. The objectives of this study were to further characterize the microbiota structure in SpA patients and to investigate the relationship between dysbiosis and disease activity in light of the putative influence of the genetic background. METHODS: Shotgun sequencing was performed on fecal DNA isolated from stool samples from 2 groups of adult volunteers: SpA patients (n = 102) and healthy controls (n = 63). A subset of the healthy controls comprised the age-matched siblings of patients whose HLA-B27 status was known. Changes in gut microbiota composition were assessed based on species diversity, enterotypes, and taxonomic and functional differences. RESULTS: Dysbiosis was confirmed in SpA patients as compared to healthy controls. The restriction of microbiota diversity was detected in patients with the most active disease, and the abundance of several bacterial species was correlated with Bath Ankylosing Spondylitis Disease Activity Index score. Among healthy controls, significant differences in microbiota composition were also detected between the HLA-B27-positive and the HLA-B27-negative siblings of SpA patients. We highlighted a decreased abundance of several species of bacteria in SpA patients, especially those bacteria belonging to the Clostridiales order. Among the few species of bacteria showing increased abundance, Ruminococcus gnavus was one of the top differentiating species. CONCLUSION: These findings reveal that genetic background and level of disease activity are likely to influence the composition of the gut microbiota of patients with SpA. It may be appropriate for further research on chronic arthritis to focus on these key parameters.

Targeted resequencing of the 13q13 spondyloarthritis-linked locus identifies a rare variant in FREM2 possibly associated with familial spondyloarthritis.

OBJECTIVES: The strong heritability of spondyloarthritis remains poorly explained, despite several large-scale association studies. A recent linkage analysis identified a new region linked to SpA on 13q13. Here we searched for variants potentially explaining this linkage signal by deep-sequencing of the region. METHODS: Re-sequencing of the 1.4 Mb target interval was performed in 92 subjects from the 43 best-linked multicases families (71 spondyloarthritis and 21 unaffected relatives), using hybridization capture-based protocol (Illumina Nextera®). Variants of interest were then genotyped by TaqMan and high resolution melting to check their co-segregation with disease in the same families and to test their association with spondyloarthritis in an independent cohort of 1,091 unrelated cases and 399 controls. Expression of FREM2 was assessed by immunostaining. RESULTS: Of the 7,563 variants identified, 24 were non-synonymous coding single-nucleotide variants. Two of them were located in the FREM2 gene on a haplotype co-segregating with the disease, including one common variant (R1840W, minor allele frequency=0.11) and one rare variant (R727H, minor allele frequency=0.0001). In the case-control analysis, there was no significant association between R1840W and spondyloarthritis (P-value=0.21), whereas R727H was not detected in any of the genotyped individuals. Immunostaining experiments revealed that FREM2 is expressed in synovial membrane, cartilage and colon. CONCLUSIONS: Targeted re-sequencing of a spondyloarthritis-linked region allowed us to identify a rare non-synonymous coding variant in FREM2, co-segregating with spondyloarthritis in a large family. This gene is expressed in several tissues relevant to spondyloarthritis pathogenesis, supporting its putative implication in spondyloarthritis.

Rheumatoid arthritis, as a clinical disease, but not rheumatoid arthritis-associated autoimmunity, is linked to cardiovascular events.

BACKGROUND: Rheumatoid arthritis (RA) is characterized by increased cardiovascular (CV) mortality. CV events are particularly high in patients with RA-specific autoimmunity, including rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA), raising the question whether RA-specific autoimmunity itself is associated with CV events. METHODS: New CV events (myocardial infarction, stroke or death by CV cause) were recorded in 20,625 subjects of the Electricité de France - Gaz de France (GAZEL) cohort. Self-reported RA cases in the GAZEL cohort were validated by phone interview on the basis of a specific questionnaire. In 1618 subjects, in whom plasma was available, RF and ACPA were measured. A piecewise exponential Poisson regression was used to analyze the association of CV events with presence of RA as well as RA-specific autoimmunity (without RA). RESULTS: CV events in GAZEL were associated with age, male sex, smoking, hypertension, hyperlipidemia, and diabetes mellitus (HR from 1.06 to 1.87, p < 0.05). Forty-two confirmed RA cases were identified. Confirmed RA was significantly associated with CV risk increase (HR of 3.03; 95% CI: 1.13-8.11, p = 0.03) independently of conventional CV risk factors. One hundred seventy-eight subjects showed RF or ACPA positivity without presence of RA. CV events were not associated with ACPA positivity (HR: 1.52, 95% CI: 0.47-4.84, p = 0.48) or RF positivity (HR: 1.15, 95% CI: 0.55-2.40, p = 0.70) in the absence of RA. CONCLUSIONS: RA, as a clinical chronic inflammatory disease, but not mere positivity for RF or ACPA in the absence of clinical disease is associated with increased CV risk.

What Have We Learned From Family-Based Studies About Spondyloarthritis?

Spondyloarthritis (SpA) is a chronic inflammatory disorder with a high familial aggregation, emphasizing the existence of genetic susceptibility factors. In the last decades, family-based studies have contributed to better understand the genetic background of SpA, in particular by showing that the most likely model of transmission is oligogenic with multiplicative effects. Coexistence of different SpA subtypes within families also highlighted the complex interplay between all subtypes. Several whole-genome linkage analyses using sib-pairs or multiplex families were performed in the 1990s to try to identify genetic susceptibility factors besides HLA-B27. Unfortunately, no consistent results were obtained and family-based studies have been progressively set aside in favor of case-control designs. In particular, case-control genome-wide association studies allowed the identification of more than 40 susceptibility regions. However, all these loci explain only a small fraction of disease predisposition. Several hypotheses have been advanced to account for this unexplained heritability, including rare variants involvement, leading to a renewed interest in family-based designs, which are probably more powerful in the detection of such variants. In this review, our purpose is to summarize what has been learned to date regarding SpA genetics from family-based studies, with a special focus on recent identification of rare associated variants through next-generation sequencing studies.

Abrupt and unexpected stressful life events are followed with increased disease activity in spondyloarthritis: A two years web-based cohort study.

OBJECTIVE: The contribution of environmental factors to spondyloarthritis (SpA) course remains poorly characterized. We previously reported a possible triggering of disease flares by stressful life events and vaccination. The objective of the present study was to specify the types of vaccine and life event that may influence disease activity. METHODS: A prospective cohort of adult SpA was followed for two years. Patients logged on to a secured website every month to complete a standardized auto-questionnaire. They reported whether they had been exposed to stressful life events, vaccinations or other environmental factors. Patients were asked to rate the distress resulting from exposure to life events on a numerical rating scale (NRS: 0-10). Primary outcome variable was the variation of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) measured on two consecutive connections. Months where an event occurred were compared to months without events. The cut-off value of 1 is defined as the minimal clinically important variation for the BASDAI. RESULTS: The 272 enrolled SpA patients returned 3,388 questionnaires. Months where an abrupt and unexpected traumatic event occurred were associated with a significant increase of BASDAI of 0.57 [95%CI: 0.29; 0.85] (P<0.001). The higher the rating of distress, the larger the impact on BASDAI, reaching a clinically meaningful increase of 0.99 [0.17; 1.82] for a VNS≥9. The effect of stressful events on BASDAI persisted during a median of 3 months. No other environmental factor was significantly associated with BASDAI variations. CONCLUSION: Among stressful life events, abrupt and unexpected events were associated with transient worsening of disease activity in SpA, which reached a clinically meaningful increase for the highest rating of distress. Association between vaccines and disease flare was not confirmed.

Faecal microbiota study reveals specific dysbiosis in spondyloarthritis.

OBJECTIVE: Altered microbiota composition or dysbiosis is suspected to be implicated in the pathogenesis of chronic inflammatory diseases, such as spondyloarthritis (SpA) and rheumatoid arthritis (RA). METHODS: 16S ribosomal RNA gene sequencing was performed on faecal DNA isolated from stool samples in two consecutive cross-sectional cohorts, each comprising three groups of adult volunteers: SpA, RA and healthy controls (HCs). In the second study, HCs comprised a majority of aged-matched siblings of patients with known HLA-B27 status. Alpha and beta diversities were assessed using QIIME, and comparisons were performed using linear discriminant analysis effect size to examine differences between groups. RESULTS: In both cohorts, dysbiosis was evidenced in SpA and RA, as compared with HCs, and was disease specific. A restriction of microbiota biodiversity was detected in both disease groups. The most striking change was a twofold to threefold increased abundance of Ruminococcus gnavus in SpA, as compared with both RA and HCs that was significant in both studies and positively correlated with disease activity in patients having a history of inflammatory bowel disease (IBD). Among HCs, significant difference in microbiota composition were also detected between HLA-B27+ and HLA-B27 negative siblings, suggesting that genetic background may influence gut microbiota composition. CONCLUSION: Our results suggest that distinctive dysbiosis characterise both SpA and RA and evidence a reproducible increase in R. gnavus that appears specific for SpA and a marker of disease activity. This observation is consistent with the known proinflammatory role of this bacteria and its association with IBD. It may provide an explanation for the link that exists between SpA and IBD.

Radiographic sacroiliitis develops predictably over time in a cohort of familial spondyloarthritis followed longitudinally.

Objectives: Radiographic sacroiliitis is an important outcome in SpA and is considered a hallmark to ascertain the diagnosis of AS. The aim of the current study was to investigate factors associated with the presence of radiographic sacroiliitis at baseline and the predictors of progression to AS in a family cohort of SpA. Methods: A total of 953 patients fulfilling the Assessment of SpondyloArthritis international Society criteria for SpA and having at least one first- or second-degree SpA-affected relative were included. Pelvic X-rays were examined blindly and independently by two qualified examiners using the modified New York criteria. Of the 446 cases without definite sacroiliitis at inclusion, 145 patients were followed up with new pelvic X-rays for 3-15 years. Regression analysis was used to assess factors associated with definite radiographic sacroiliitis. Results: Factors independently associated with radiographic sacroiliitis at inclusion were male sex, younger age at disease onset, longer disease duration, inflammatory back pain, uveitis and lack of enthesitis. During the follow-up, 27.3% of the patients with axial SpA developed definite sacroiliitis, whereas there was no progression in patients with peripheral SpA. After 15 years of follow-up, a Kaplan-Meier estimate of the proportion of patients with definite radiographic sacroiliitis reached 68.5%. Factors associated with progression to definite sacroiliitis were a low-grade radiographic sacroiliitis at inclusion, occurrence of buttock pain and the absence of peripheral arthritis during the follow-up period. Conclusions: These data confirm that progression to radiographic disease occurs most often over time in axial SpA patients.

A family-based genome-wide association study reveals an association of spondyloarthritis with MAPK14.

OBJECTIVE: More than 40 loci have been associated with ankylosing spondylitis (AS), but less is known about genetic associations in spondyloarthritis (SpA) as a whole. We conducted a family-based genome-wide association study (GWAS) to identify new non-major histocompatibility complex (MHC) genetic factors associated with SpA. METHODS: 906 subjects from 156 French multiplex families, including 438 with SpA, were genotyped using Affymetrix 250K microarrays. Association was tested with Unphased. The best-associated non-MHC single nucleotide polymorphisms (SNPs) were then genotyped in two independent familial cohorts (including 215 French and 294 North American patients with SpA, respectively) to replicate associations. RESULTS: 43 non-MHC SNPs yielded an association signal with SpA in the discovery cohort (p<1×10-4). In the extension studies, association was replicated at a nominal p value of p<0.05 for 16 SNPs in the second cohort and for three SNPs in the third cohort. Combined analysis identified an association close to genome-wide significance between rs7761118, an intronic SNP of MAPK14, and SpA (p=3.5×10-7). Such association appeared to be independent of HLA-B27. CONCLUSIONS: We report here for the first time a family-based GWAS study on SpA and identified an associated polymorphism near MAPK14. Further analyses are needed to better understand the functional basis of this genetic association.

Whole-genome single nucleotide polymorphism-based linkage analysis in spondyloarthritis multiplex families reveals a new susceptibility locus in 13q13.

OBJECTIVE: Spondyloarthritis (SpA) is a chronic inflammatory disorder with high heritability but with complex genetics. Apart from HLA-B27, most of the underlying genetic components remain to be identified. We conducted a whole-genome high-density non-parametric linkage analysis to identify new genetic factors of susceptibility to SpA. METHODS: 914 subjects including 462 with SpA from 143 multiplex families were genotyped using Affymetrix 250K microarrays. After quality control, 189 368 single nucleotide polymorphisms (SNPs) were kept for further analyses. Both non-parametric and parametric linkage analyses were performed using Merlin software. Association was tested with Unphased. RESULTS: Non-parametric linkage analysis identified two regions significantly linked to SpA: the major histocompatibility complex (LODmax=24.77) and a new 13q13 locus (LODmax=5.03). Additionally, eight loci achieved suggestive LOD scores, including the previously identified SPA2 locus at 9q33 (LODmax=3.51). Parametric analysis supported a codominant model in 13q13 with a maximum heterogeneity LOD, 'HLOD' score of 3.084 (α=0.28). Identification of meiotic recombination events around the 13q13 linkage peak in affected subjects from the 43 best-linked families allowed us to map the disease interval between 38.753 and 40.040 Mb. Family-based association analysis of the SNPs inside this interval in the best-linked families identified a SNP near FREM2 (rs1945502) which reached a p value close to statistical significance (corrected p=0.08). CONCLUSION: We report here for the first time a significant linkage between 13q13 and SpA. Identification of susceptibility factor inside this chromosomal region through targeted sequencing in linked families is underway.

ERAP1 Gene Expression Is Influenced by Nonsynonymous Polymorphisms Associated With Predisposition to Spondyloarthritis.

OBJECTIVE: Several polymorphisms in ERAP1 are strongly associated with susceptibility to spondyloarthritis (SpA). The combination of rs17482078, rs10050860, and rs30187 results in the construction of 3 major haplotypes that are associated with SpA (the "protective" haplotype T/T/C, the "neutral" haplotype C/C/C, and the "susceptibility" haplotype C/C/T). The aim of the present study was to determine whether such haplotypes might affect endoplasmic reticulum aminopeptidase 1 (ERAP-1) messenger RNA (mRNA) expression, protein level, and/or enzymatic activity in antigen-presenting cells, a type of cell that is potentially relevant to disease pathogenesis. METHODS: Monocyte-derived dendritic cells (DCs) were generated in 2 cohorts (a discovery cohort and a replication cohort) comprising a total of 23 SpA patients and 44 healthy controls. Lymphoblastoid B cell lines were established from individuals who were homozygous for the risk, the neutral, or the protective ERAP1 haplotype, respectively. In those samples, we investigated the relationship between ERAP1 haplotypes and mRNA expression level. We also used Western blot analysis to measure the relative protein expression of ERAP-1 and a fluorogenic assay to measure its enzymatic activity. RESULTS: In monocyte-derived DCs, there was a strong association between ERAP1 haplotypes and the ERAP-1 mRNA expression level, with higher levels in subjects harboring the susceptibility haplotype (P = 0.001 and P = 5.6 × 10(-7) in the discovery and replication cohorts, respectively). In lymphoblastoid B cell lines, we observed a significant correlation between haplotype risk score and ERAP1 transcript or protein level (P = 0.003, ρ = 0.92 for both). Enzymatic activity followed a similar trend both in monocyte-derived DCs and in lymphoblastoid B cell lines. CONCLUSION: These data provide strong evidence that SpA-associated ERAP1 polymorphisms affect the level of gene expression in antigen-presenting cells. How increased production/activity of ERAP-1 may influence susceptibility to SpA remains to be determined.

Prevalence of spondyloarthritis in reference to HLA-B27 in the French population: results of the GAZEL cohort.

OBJECTIVE: To estimate the prevalence of spondyloarthritis (SpA) in reference to HLA-B27 in the French population. METHODS: In 1989, 20 625 employees of the French national gas and electricity company aged 35-50 years were enrolled in the GAZEL cohort. In 2010, 18 757 still active participants were screened by a questionnaire validated for the detection of SpA. Responders with available DNA were retained for further studies. Pelvic radiograph and HLA-B27 typing were performed in all the self-reported cases of SpA or psoriatic arthritis. Self-reported diagnosis was verified by a qualified rheumatologist. HLA-B27 determination was also performed in subjects without any SpA feature. RESULTS: The target population consisted of 6556 responders with available DNA. Their male:female ratio was 3.6 and their mean age was 65.5±3.3 years. A diagnosis of SpA was confirmed in 32 of the 72 self-reported cases, 75% of them being HLA-B27 positive. Estimated SpA prevalence adjusted for sex was 0.43% (95% CI 0.26% to 0.70%). HLA-B27 positivity rate in 2466 healthy controls was 6.9% (95% CI 5.9% to 7.9%). The relative risk of SpA in HLA-B27 positive individuals was 39 (95% CI 17 to 86). CONCLUSIONS: We estimated the prevalence of SpA in the French population in 2010 to 0.43%. With an estimated prevalence of 75.0% in SpA and 6.9% in healthy controls, HLA-B27 increased the disease risk 39-fold, as compared with HLA-B27 negative subjects.

Brief report: the IL23R nonsynonymous polymorphism rs11209026 is associated with radiographic sacroiliitis in spondyloarthritis.

OBJECTIVE: Spondyloarthritis (SpA) is a group of inflammatory articular disorders sharing a genetic background. The nonsynonymous single-nucleotide polymorphism (SNP) rs11209026 (Arg381Gln) in the IL23R gene has reproducibly been shown to be associated with ankylosing spondylitis (AS). We undertook this study to examine the association between rs11209026 and SpA as a whole, with particular attention devoted to genotype/phenotype correlation. METHODS: The SNP rs11209026 was genotyped in a French cohort of 415 patients/372 controls, with replication analysis performed in 383 "trios," each consisting of 1 patient with SpA and both parents. Association analysis was carried out in SpA as a whole group and then separately in AS and non-AS patients. Phenotype/genotype correlations were examined using logistic regression analysis. RESULTS: A significant association between rs11209026 and SpA overall was identified only in the familial data set (odds ratio 0.57, P=0.028). Strong association with AS was observed in both the case-control and familial data sets (P=4.5×10(-4) and P=4.0×10(-3), respectively). In contrast, such association was not detected in the non-AS group. Furthermore, rs11209026 frequency was significantly different between AS and non-AS patients (P=1.5×10(-3)). Phenotype/genotype correlation study revealed that both radiographic sacroiliitis and early age at onset were independently associated with a lower frequency of the rare protective rs11209026 allele A in patients (P=9×10(-3) and P=8×10(-3), respectively). CONCLUSION: Our study replicated the robust association between rs11209026 and AS in the French population. However, such association was restricted to AS, as compared to SpA without radiographic sacroiliitis. The fact that it was independently conditional on radiographic sacroiliitis and age at onset suggests that rs11209026 could affect disease severity rather than susceptibility.

Investigating the genetic association between ERAP1 and spondyloarthritis.

OBJECTIVE: A robust association between polymorphisms in the non-major histocompatibility complex gene ERAP1 and ankylosing spondylitis (AS) in several populations was recently identified. The aim of the current study was to determine the level of association of ERAP1 polymorphisms with spondyloarthritis (SpA) in French/Belgian populations with particular attention to genotype-phenotype correlations. METHODS: We studied 734 independent SpA cases and 632 controls from two European cohorts. Five single-nucleotide polymorphisms (SNPs), rs27044, rs17482078, rs10050860, rs30187 and rs2287987 were genotyped, and case-control association analyses were carried using PLINK 1.07 software. Linkage disequilibrium and haplotypes were estimated with Haploview. Analysis was first carried out in SpA as a whole group, and then separately in AS and non-radiographic SpA (non-AS) patients. RESULTS: Consistent with previous studies conducted in AS, rs30187 was the most significantly associated SNP with SpA (p=0.008 in the French, and p=6.46×10(-4) in the Belgian cohorts). In the combined cohorts, this SNP was associated with both AS and non-AS (P(combined)= 3.9×10(-5) and P(combined)= 0.005, respectively). A similar trend was observed with other SNPs. The rs17482078/rs10050860/rs30187-CCT haplotype was significantly associated with increased risk of SpA in both cohorts (P(combined)= 9.08×10(-4)), including AS and non-AS (P(combined)=6.16×10(-4) and P(combined)=0.049, respectively), whereas the -TTC haplotype was associated with reduced risk of SpA, including AS and non-AS (P(combined)=2.36×10(-7), P(combined)= 5.69×10(-6) and P(combined)= 2.13×10(-4), respectively). CONCLUSIONS: This is the first study to show an association between several polymorphisms located in ERAP1 and SpA as a whole. Our findings demonstrate consistent association of the same SNPs and haplotypes with both AS and non-AS subtypes of SpA.

Can we improve the diagnosis of spondyloarthritis in patients with uncertain diagnosis? The EchoSpA prospective multicenter French cohort.

UNLABELLED: Power Doppler ultrasound (PDUS) has proved to be a highly sensitive tool for assessing enthesitis in spondyloarthritis (SpA). In patients with a suspected SpA, diagnosis could be improved by detecting enthesitis with PDUS. OBJECTIVE: To evaluate the performance of PDUS for the diagnosis of SpA alone or combined with other clinical, laboratory and imaging findings in patients consulting for a suspected SpA. METHODS: Prospective, multicenter French cohort study (Boulogne-Billancourt, Brest, Caen, Grenoble, Marseille and Nancy). Outpatients consulting for symptoms suggestive of SpA (inflammatory back pain [IBP], arthritis or inflammatory arthralgia [IA], enthesitis or dactylitis [ED], HLA-B27 positive uveitis [B27+U], familiarity for SpA [Fam]) were recruited and followed up for at least 2 years. Sample size was set to 500 patients (for estimated prevalence of SpA of 30±5% after 2 years). At baseline, patients were submitted to standardized physical examination, pelvic X-ray, sacroiliac joints magnetic resonance imaging (MRI), HLA-B typing, and other tests judged useful for diagnosis. For each patient, a blinded PDUS examination of 14 enthesitic sites was performed at baseline and at years 1 and 2. Patients were planned to be followed during 5 years. The diagnosis of SpA ascertained by an experts' committee, blind to PDUS results, after at least 2 years of follow-up, with a revaluation of doubtful patients at 5 years will be used as gold standard for evaluating the diagnostic performance of PDUS and the best diagnostic procedure by combining PDUS, clinical symptoms and other tests. RESULTS: Between January 2005 and September 2007, 489 patients were included (96% of the target population). Nineteen patients (0.2%) retired their informed consensus or were lost to follow-up immediately after their inclusion. At baseline, mean age of the 470 remaining patients was 40 years, mean duration of symptoms was 6.1 years; 42% of them were HLA-B27+ and 63% were female. Primary inclusion criterion was IBP in 53%, IA in 27%, ED in 9%, B27+U in 8% and Fam in 4%. Follow-up is still ongoing. CONCLUSION: We have set up a unique diagnostic cohort which includes the entire spectrum of SpA manifestations. By using PDUS we expected to improve the diagnostic procedure of SpA.

Association between the IL-1 family gene cluster and spondyloarthritis.

OBJECTIVE: Spondyloarthritis is a group of articular disorders sharing a genetic background. Polymorphisms in the IL-1 gene cluster have previously been associated with ankylosing spondylitis (AS), a subset of spondyloarthritis. This study examined the association between several of these polymorphisms and the whole spondyloarthritis. Particular attention was devoted to genotype-phenotype correlations. METHODS: Seven single-nucleotide polymorphisms (SNP) and a variable number tandem repeat located in the IL-1 gene cluster were genotyped in 185 independent spondyloarthritis trios. Family-based association test (FBAT) was computed using the FBAT software. Analysis was carried in spondyloarthritis as a whole and also in AS. A case-control replication study was performed for four of the SNP, in an independent sample of 414 spondyloarthritis and 264 controls. A combined analysis of both studies was performed. RESULTS: The SNP rs2856836 in IL1A was significantly associated with spondyloarthritis (p=0.009) and AS (p=0.010) in the family study. The case-control study revealed an association between another IL1A variant (rs1894399) and AS (p=0.035), and between IL1F10.3 (rs3811058) and spondyloarthritis (p=0.041). By combining family and case-control studies an association between AS and IL1A was confirmed (rs1894399, p=0.024), whereas non-AS was more significantly associated with IL1F10.3 (p=0.0043). Family-based and case-control studies revealed significant association between the two most frequent haplotypes combining the four SNP of the replication study and both spondyloarthritis (p=0.0054 and p=0.038) and AS phenotypes (p=0.018 and 0.0036). CONCLUSION: This study is the first to demonstrate an association between several polymorphisms located in the IL-1 gene cluster and spondyloarthritis as a whole. The IL1A locus was strongly associated with AS phenotype, whereas IL1F10 was associated with non-AS.

Systematic candidate gene investigations in the SPA2 locus (9q32) show an association between TNFSF8 and susceptibility to spondylarthritis.

OBJECTIVE: Our group previously identified a new susceptibility region linked to spondylarthritis (SpA) on chromosome 9q31-34. Fine mapping of this SPA2 locus allowed us to refine the peak of linkage to a 1.3-Mb interval. The objective of this study was to resequence most positional candidate genes lying in that region, to identify polymorphisms, and to examine their association with SpA. METHODS: Variants screening was performed in 30 independent patients with SpA from families with a high linkage score to the SPA2 locus and 30 control subjects. The coding regions, intron-exon boundaries, and 5'- and 3'-flanking regions of ZNF618, A1L4R1_HUMAN (AF495724), AMBP, KIF12, ORM1, ORM2, C9ORF91, ENSESTG000000230601, and TNFSF8 were resequenced to identify polymorphisms. Selected variants were genotyped in an extended French cohort (442 patients and 268 control subjects overall). Replication was performed in a combined Belgian and Portuguese cohort (433 patients and 299 control subjects). RESULTS: Variants screening allowed us to identify 98 polymorphisms, 5 of which were selected for further studies, based on statistical significance. The rare intronic single-nucleotide polymorphism (SNP) rs3181357, located in TNFSF8, was significantly associated with SpA in the French and the replication cohorts (odds ratio [OR] 2.03, P = 0.009 and OR 2.26, P = 0.0014, respectively) and in the pooled analysis (OR 2.14, P = 0.0001). CONCLUSION: Positional candidate gene screening in the SPA2 locus allowed us to identify and replicate an association between a rare SNP located in TNFSF8 and SpA. This new finding appears to be independent of an association with a haplotype near TNFSF15, which we recently reported.

Prospective assessment of thoracic kyphosis in postmenopausal women with osteoporosis.

We attempt to assess quantitatively thoracic kyphosis and its influence on incident fractures and quality of life over three years in postmenopausal women with osteoporosis and the effect of strontium ranelate on thoracic kyphosis progression. This study was performed on women with postmenopausal osteoporosis from the Spinal Osteoporosis Therapeutic Intervention (SOTI) and Treatment of Peripheral Osteoporosis (TROPOS) studies. Vertebral fractures were assessed on lateral thoracic radiographs performed at baseline and at three years according to standardized procedure. Kyphosis index (KI, %), was defined as the percentage ratio between the maximum depth of thoracic curvature and the height measured from the T4 to the T12 vertebrae. Baseline characteristics of the 3218 patients (1594 strontium ranelate, 1624 placebo) were mean age 73.3 years, spine bone mineral density (BMD) T-score (L2-4) -3.1, femoral neck T-score -3.0, and KI 25.4%. In the placebo group, patients with the highest baseline KI experienced significantly more vertebral fractures than those with medium KIs [relative risk (RR) = 1.53; 95% confidence interval (CI) 1.19-1.96, p < .001) or the lowest KIs (RR = 1.70, 95%CI 1.32-2.21, p < .001), even after adjusting for the presence of prevalent fractures, age, body mass index (BMI), and BMD. There was no difference in the risk of nonvertebral fractures according to baseline KI. Three-year changes in quality-of-life physical scores reflected significantly better status for patients in the lowest tertile of KI compared with those in the highest at baseline. Over three years, the KI increased for all patients, indicating worsening of thoracic kyphosis, whatever the presence of prevalent or incident vertebral fractures. This KI progression was lower in the strontium ranelate group than in the placebo group. Thoracic kyphosis is a risk factor for vertebral fractures over three years and influences physical capacity changes in postmenopausal women with osteoporosis. Thoracic kyphosis progression over three years is lower in a subgroup of strontium ranelate-treated patients compared with placebo-treated patients.

Comprehensive linkage and association analyses identify haplotype, near to the TNFSF15 gene, significantly associated with spondyloarthritis.

Spondyloarthritis (SpA) is a chronic inflammatory disorder with a strong genetic predisposition dominated by the role of HLA-B27. However, the contribution of other genes to the disease susceptibility has been clearly demonstrated. We previously reported significant evidence of linkage of SpA to chromosome 9q31-34. The current study aimed to characterize this locus, named SPA2. First, we performed a fine linkage mapping of SPA2 (24 cM) with 28 microsatellite markers in 149 multiplex families, which allowed us to reduce the area of investigation to an 18 cM (13 Mb) locus delimited by the markers D9S279 and D9S112. Second, we constructed a linkage disequilibrium (LD) map of this region with 1,536 tag single-nucleotide polymorphisms (SNPs) in 136 families (263 patients). The association was assessed using a transmission disequilibrium test. One tag SNP, rs4979459, yielded a significant P-value (4.9 x 10(-5)). Third, we performed an extension association study with rs4979459 and 30 surrounding SNPs in LD with it, in 287 families (668 patients), and in a sample of 139 cases and 163 controls. Strong association was observed in both familial and case/control datasets for several SNPs. In the replication study, carried with 8 SNPs in an independent sample of 232 cases and 149 controls, one SNP, rs6478105, yielded a nominal P-value<3 x 10(-2). Pooled case/control study (371 cases and 312 controls) as well as combined analysis of extension and replication data showed very significant association (P<5 x 10(-4)) for 6 of the 8 latter markers (rs7849556, rs10817669, rs10759734, rs6478105, rs10982396, and rs10733612). Finally, haplotype association investigations identified a strongly associated haplotype (P<8.8 x 10(-5)) consisting of these 6 SNPs and located in the direct vicinity of the TNFSF15 gene. In conclusion, we have identified within the SPA2 locus a haplotype strongly associated with predisposition to SpA which is located near to TNFSF15, one of the major candidate genes in this region.

The genetics of spondyloarthropathies.

The spondyloarthropathies constitute a group of inflammatory joint diseases linked by shared characteristics that include a strong common genetic background. Genetic factors include major histocompatibility complex (MHC) genes, among which HLA-B27 contributes 30% of the overall genetic susceptibility to spondyloarthropathies, and non-MHC genes, none of which have been identified to date. Genome screens have identified regions that may contain susceptibility genes for spondyloarthropathies. In particular, a locus on the long arm of chromosome 9 (9q31-34) was identified by two groups working independently from each other. Studies using the candidate gene approach ruled out a role for most of the tested genes, including CARD15/NOD2. However, several independent groups have reported significant associations between ankylosing spondylitis and the IL-1 gene cluster on the long arm of chromosome 2.