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Objectives: The analysis of annotated transcripts from genome-wide expression studies may help to understand the pathogenesis of complex diseases, such as systemic sclerosis (SSc). We performed a whole blood (WB) transcriptome analysis on RNA collected in the context of the European PRECISESADS project, aiming at characterising the pathways that differentiate SSc from controls and that are reproducible in geographically diverse populations.Methods: Samples from 162 patients and 252 controls were collected in RNA stabilisers. Cases and controls were divided into a discovery (n=79+163; Southern Europe) and validation cohort (n=83+89; Central-Western Europe). RNA sequencing was performed by an Illumina assay. Functional annotations of Reactome pathways were performed with the Functional Analysis of Individual Microarray Expression (FAIME) algorithm. In parallel, immunophenotyping of 28 circulating cell populations was performed. We tested the presence of differentially expressed genes/pathways and the correlation between absolute cell counts and RNA transcripts/FAIME scores in regression models. Results significant in both populations were considered as replicated.Results: Overall, 15 224 genes and 1277 functional pathways were available; of these, 99 and 225 were significant in both sets. Among replicated pathways, we found a deregulation in type-I interferon, Toll-like receptor cascade, tumour suppressor p53 protein function, platelet degranulation and activation. RNA transcripts or FAIME scores were jointly correlated with cell subtypes with strong geographical differences; neutrophils were the major determinant of gene expression in SSc-WB samples.Conclusions: We discovered a set of differentially expressed genes/pathways validated in two independent sets of patients with SSc, highlighting a number of deregulated processes that have relevance for the pathogenesis of autoimmunity and SSc. [ABSTRACT FROM AUTHOR]

Objective: To determine whether genetic substructure in European-derived populations is associated with specific manifestations of systemic lupus erythematosus (SLE), including mucocutaneous phenotypes, autoantibody production, and renal disease., Methods: SLE patients of European descent (n=1,754) from 8 case collections were genotyped for >1,400 ancestry informative markers that define a north-south gradient of European substructure. Using the Structure program, each SLE patient was characterized in terms of percent Northern (versus percent Southern) European ancestry based on these genetic markers. Nonparametric methods, including tests for trend, were used to identify associations between Northern European ancestry and specific SLE manifestations., Results: In multivariate analyses, increasing levels of Northern European ancestry were significantly associated with photosensitivity (Ptrend=0.0021, odds ratio for highest quartile of Northern European ancestry versus lowest quartile [ORhigh-low] 1.64, 95% confidence interval [95% CI] 1.13-2.35) and discoid rash (Ptrend=0.014, ORhigh-low 1.93, 95% CI 0.98-3.83). In contrast, increasing levels of Northern European ancestry had a protective effect against the production of anticardiolipin autoantibodies (Ptrend=1.6x10(-4), ORhigh-low 0.46, 95% CI 0.30-0.69) and anti-double-stranded DNA autoantibodies (Ptrend=0.017, ORhigh-low 0.67, 95% CI 0.46-0.96)., Conclusion: This study demonstrates that specific SLE manifestations vary according to Northern versus Southern European ancestry. Thus, genetic ancestry may contribute to the clinical heterogeneity and variation in disease outcomes among SLE patients of European descent. Moreover, these results suggest that genetic studies of SLE subphenotypes will need to carefully address issues of population substructure based on genetic ancestry.

The IRF5 gene was found to be strongly associated with SLE. We identified two functional polymorphisms and recently an insertion/deletion together with a tag SNP defining the risk haplotype in individuals of European ancestry. We now analyzed sets of Mexican patients with SLE. Three polymorphisms in the IRF5 gene were genotyped in two sets of Mexican individuals with SLE and controls as well as in families including a set of pediatric SLE patients. A set of healthy Mexican Indians was also typed. Genetic association with SLE was found for all three polymorphisms. The genetic association was very strong in the case-control analysis in both sets (for SNP rs2070197, combined P = 1.26 x 10(-21)) and in families (combined P = 0.000004). Compared to healthy individuals with European ancestry, the frequency of the risk haplotype in healthy Mexican individuals was significantly higher and even higher in the healthy Mexican Indian group. Further, a much higher frequency of the risk haplotype and of individual homozygote for it was found among Mexican SLE patients. The significantly higher frequency of homozygote individuals for the risk haplotype among Mexican SLE patients could be the result of genetic admixture, and suggests the possibility that IRF5 could be involved in the more active disease and organ involvement known to occur among Mexican SLE patients.

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies against intracellular components, the formation of immune complexes, and inflammation in various organs, typically the skin and kidney glomeruli. The etiology of the disease is not well understood but is most likely the result of the interaction between genetic and environmental factors. In order to identify susceptibility loci for SLE, we have performed genome scans with microsatellite markers covering the whole genome in families from Argentina, Italy, and Europe. The results reveal a heterogeneous disease with different susceptibility loci in different family sets. We have found significant linkage to chromosome 17p12-q11 in the Argentine set of families. The maximum LOD score was given by marker D17S1294 in combination with D17S1293, when assuming a dominant inheritance model (Z = 3.88). We also analyzed a repeat in the promoter region of the NOS2A gene, a strong candidate gene in the region, but no association was found. The locus on chromosome 17 has previously been identified in genetic studies of multiple sclerosis families. Several other interesting regions were found at 1p35, 1q31, 3q26, 5p15, 11q23 and 19q13, confirming previously identified loci for SLE or other autoimmune diseases., (Copyright 2004 Springer-Verlag)