Identification of clinically relevant genetic variation in immune-mediated inflammatory diseases using genome-wide approaches

Rheumatoid arthritis, psoriasis, psoriatic arthritis, systemic lupus erythematosus, Crohn’s disease and ulcerative colitis are six of the most prevalent immune-mediated inflammatory diseases (IMIDs) and are associated with a high socio-economic impact. There is compelling evidence that IMIDs are genetically complex diseases. To date, however, the genetic component of IMIDs has been only partially explained. Identifying new clinically relevant variation is therefore of major clinical interest. The objective of the present thesis was to identify new genetic variation underlying IMIDs. The research activity here presented is the result of analyzing high-throughput genomic data from a large cohort of IMID patients collected by the IMID Consortium. Using genome-wide approaches and functional analyses, we have identified new genetic variants associated to IMID susceptibility, IMID clinical phenotypes and specific treatment outcomes. Taken together, these findings contribute to better understanding the genetic basis of IMIDs and suggest more specific and preventive therapeutic strategies.L’artritis reumatoide, la psoriasis, l’artritis psoriàsica, el lupus eritematós sistèmic, la malaltia de Crohn i la colitis ulcerosa són sis malalties inflamatòries mediades per immunitat (IMIDs) d’elevada prevalença i amb un fort impacte socioeconòmic. Totes elles comparteixen un component genètic important. No obstant, a dia d’avui, només s’ha caracteritzat una part dels factors genètics de les IMIDs. La identificació de factors genètics clínicament rellevants presenta doncs un gran interès clínic per tal d’incorporar la informació genètica a la pràctica mèdica. L’objectiu d’aquesta tesi és identificar noves variants genètiques associades a les IMIDs. La recerca que es presenta és el resultat d’analitzar dades genòmiques d’una gran cohort de pacients amb IMIDs, els quals es van obtenir a través del consorci IMID Consortium. Mitjançant estratègies d’anàlisi de genoma complet i estudis funcionals, en aquesta tesi s’han identificat noves variants genètiques associades al risc de desenvolupar IMIDs així com als seus fenotips clínics i tractament. Aquesta tesi contribueix significativament a la caracterització del component genètic de les IMIDs i, des d’un punt de vista clínic, suggereix noves estratègies terapèutiques

Genetic variation associated with cardiovascular risk in autoimmune diseases

Autoimmune diseases have a higher prevalence of cardiovascular events compared to the general population. The objective of this study was to investigate the genetic basis of cardiovascular disease (CVD) risk in autoimmunity. We analyzed genome-wide genotyping data from 6,485 patients from six autoimmune diseases that are associated with a high socio-economic impact. First, for each disease, we tested the association of established CVD risk loci. Second, we analyzed the association of autoimmune disease susceptibility loci with CVD. Finally, to identify genetic patterns associated with CVD risk, we applied the cross-phenotype meta-analysis approach (CPMA) on the genome-wide data. A total of 17 established CVD risk loci were significantly associated with CVD in the autoimmune patient cohorts. From these, four loci were found to have significantly different genetic effects across autoimmune diseases. Six autoimmune susceptibility loci were also found to be associated with CVD risk. Genome-wide CPMA analysis identified 10 genetic clusters strongly associated with CVD risk across all autoimmune diseases. Two of these clusters are highly enriched in pathways previously associated with autoimmune disease etiology (TNF? and IFN? cytokine pathways). The results of this study support the presence of specific genetic variation associated with the increase of CVD risk observed in autoimmunity

Genome-wide pathway analysis identifies VEGF pathway association with oral ulceration in systemic lupus erythematosus

Background: Systemic lupus erythematosus (SLE) is a genetically complex rheumatic disease characterized by heterogeneous clinical manifestations of unknown etiology. Recent studies have suggested the existence of a genetic basis for SLE heterogeneity. The objective of the present study was to identify new genetic variation associated with the clinically relevant phenotypes in SLE. Methods: A two-stage pathway-based approach was used to identify the genetic variation associated with the main clinical phenotypes in SLE. In the discovery stage, 482 SLE patients were genotyped using Illumina Human Quad610 microarrays. Association between 798 reference genetic pathways from the Molecular Signatures Database and 11 SLE phenotypes was tested using the set-based method implemented in PLINK software. Pathways significantly associated after multiple test correction were subsequently tested for replication in an independent cohort of 425 SLE patients. Using an in silico approach, we analyzed the functional effects of common SLE therapies on the replicated genetic pathways. The association of known SLE risk variants with the development of the clinical phenotypes was also analyzed. Results: In the discovery stage, we found a significant association between the vascular endothelial growth factor (VEGF) pathway and oral ulceration (P value for false discovery rate (P FDR) < 0.05), and between the negative regulation signaling pathway of retinoic acid inducible gene-I/melanoma differentiation associated gene 5 and the production of antinuclear antibodies (P FDR < 0.05). In the replication stage, we validated the association between the VEGF pathway and oral ulceration. Therapies commonly used to treat mucocutaneous phenotypes in SLE were found to strongly influence VEGF pathway gene expression (P = 4.60e-4 to 5.38e-14). Analysis of known SLE risk loci identified a strong association between PTPN22 and the risk of hematologic disorder and with the development of antinuclear antibodies. Conclusions: The present study has identified VEGF genetic pathway association with the risk of oral ulceration in SLE. New therapies targeting the VEGF pathway could be more effective in reducing the severity of this phenotype. These findings represent a first step towards the understanding of the genetic basis of phenotype heterogeneity in SLE

Identification of clinically relevant genetic variation in immune-mediated inflammatory diseases using genome-wide approaches

Rheumatoid arthritis, psoriasis, psoriatic arthritis, systemic lupus erythematosus, Crohn’s disease and ulcerative colitis are six of the most prevalent immune-mediated inflammatory diseases (IMIDs) and are associated with a high socio-economic impact. There is compelling evidence that IMIDs are genetically complex diseases. To date, however, the genetic component of IMIDs has been only partially explained. Identifying new clinically relevant variation is therefore of major clinical interest. The objective of the present thesis was to identify new genetic variation underlying IMIDs. The research activity here presented is the result of analyzing high-throughput genomic data from a large cohort of IMID patients collected by the IMID Consortium. Using genome-wide approaches and functional analyses, we have identified new genetic variants associated to IMID susceptibility, IMID clinical phenotypes and specific treatment outcomes. Taken together, these findings contribute to better understanding the genetic basis of IMIDs and suggest more specific and preventive therapeutic strategies.L’artritis reumatoide, la psoriasis, l’artritis psoriàsica, el lupus eritematós sistèmic, la malaltia de Crohn i la colitis ulcerosa són sis malalties inflamatòries mediades per immunitat (IMIDs) d’elevada prevalença i amb un fort impacte socioeconòmic. Totes elles comparteixen un component genètic important. No obstant, a dia d’avui, només s’ha caracteritzat una part dels factors genètics de les IMIDs. La identificació de factors genètics clínicament rellevants presenta doncs un gran interès clínic per tal d’incorporar la informació genètica a la pràctica mèdica. L’objectiu d’aquesta tesi és identificar noves variants genètiques associades a les IMIDs. La recerca que es presenta és el resultat d’analitzar dades genòmiques d’una gran cohort de pacients amb IMIDs, els quals es van obtenir a través del consorci IMID Consortium. Mitjançant estratègies d’anàlisi de genoma complet i estudis funcionals, en aquesta tesi s’han identificat noves variants genètiques associades al risc de desenvolupar IMIDs així com als seus fenotips clínics i tractament. Aquesta tesi contribueix significativament a la caracterització del component genètic de les IMIDs i, des d’un punt de vista clínic, suggereix noves estratègies terapèutiques

Genetic variation at the glycosaminoglycan metabolism pathway contributes to the risk of psoriatic arthritis but not psoriasis

OBJECTIVE: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis affecting up to 30% of patients with psoriasis (Ps). To date, most of the known risk loci for PsA are shared with Ps, and identifying disease-specific variation has proven very challenging. The objective of the present study was to identify genetic variation specific for PsA. METHODS: We performed a genome-wide association study in a cohort of 835 patients with PsA and 1558 controls from Spain. Genetic association was tested at the single marker level and at the pathway level. Meta-analysis was performed with a case-control cohort of 2847 individuals from North America. To confirm the specificity of the genetic associations with PsA, we tested the associated variation using a purely cutaneous psoriasis cohort (PsC, n=614) and a rheumatoid arthritis cohort (RA, n=1191). Using network and drug-repurposing analyses, we further investigated the potential of the PsA-specific associations to guide the development of new drugs in PsA. RESULTS: We identified a new PsA risk single-nucleotide polymorphism at B3GNT2 locus (p=1.10e-08). At the pathway level, we found 14 genetic pathways significantly associated with PsA (pFDR<0.05). From these, the glycosaminoglycan (GAG) metabolism pathway was confirmed to be disease-specific after comparing the PsA cohort with the cohorts of patients with PsC and RA. Finally, we identified candidate drug targets in the GAG metabolism pathway as well as new PsA indications for approved drugs. CONCLUSION: These findings provide insights into the biological mechanisms that are specific for PsA and could contribute to develop more effective therapies

Genome-wide pathway analysis identifies VEGF pathway association with oral ulceration in systemic lupus erythematosus

Includes supplementary materials for the online appendix.Systemic lupus erythematosus (SLE) is a genetically complex rheumatic disease characterized by heterogeneous clinical manifestations of unknown etiology. Recent studies have suggested the existence of a genetic basis for SLE heterogeneity. The objective of the present study was to identify new genetic variation associated with the clinically relevant phenotypes in SLE. A two-stage pathway-based approach was used to identify the genetic variation associated with the main clinical phenotypes in SLE. In the discovery stage, 482 SLE patients were genotyped using Illumina Human Quad610 microarrays. Association between 798 reference genetic pathways from the Molecular Signatures Database and 11 SLE phenotypes was tested using the set-based method implemented in PLINK software. Pathways significantly associated after multiple test correction were subsequently tested for replication in an independent cohort of 425 SLE patients. Using an in silico approach, we analyzed the functional effects of common SLE therapies on the replicated genetic pathways. The association of known SLE risk variants with the development of the clinical phenotypes was also analyzed. In the discovery stage, we found a significant association between the vascular endothelial growth factor (VEGF) pathway and oral ulceration (P value for false discovery rate (P FDR) < 0.05), and between the negative regulation signaling pathway of retinoic acid inducible gene-I/melanoma differentiation associated gene 5 and the production of antinuclear antibodies (P FDR < 0.05). In the replication stage, we validated the association between the VEGF pathway and oral ulceration. Therapies commonly used to treat mucocutaneous phenotypes in SLE were found to strongly influence VEGF pathway gene expression (P = 4.60e-4 to 5.38e-14). Analysis of known SLE risk loci identified a strong association between PTPN22 and the risk of hematologic disorder and with the development of antinuclear antibodies. The present study has identified VEGF genetic pathway association with the risk of oral ulceration in SLE. New therapies targeting the VEGF pathway could be more effective in reducing the severity of this phenotype. These findings represent a first step towards the understanding of the genetic basis of phenotype heterogeneity in SLE

Genetic variation at the glycosaminoglycan metabolism pathway contributes to the risk of psoriatic arthritis but not psoriasis

OBJECTIVE: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis affecting up to 30% of patients with psoriasis (Ps). To date, most of the known risk loci for PsA are shared with Ps, and identifying disease-specific variation has proven very challenging. The objective of the present study was to identify genetic variation specific for PsA. METHODS: We performed a genome-wide association study in a cohort of 835 patients with PsA and 1558 controls from Spain. Genetic association was tested at the single marker level and at the pathway level. Meta-analysis was performed with a case-control cohort of 2847 individuals from North America. To confirm the specificity of the genetic associations with PsA, we tested the associated variation using a purely cutaneous psoriasis cohort (PsC, n=614) and a rheumatoid arthritis cohort (RA, n=1191). Using network and drug-repurposing analyses, we further investigated the potential of the PsA-specific associations to guide the development of new drugs in PsA. RESULTS: We identified a new PsA risk single-nucleotide polymorphism at B3GNT2 locus (p=1.10e-08). At the pathway level, we found 14 genetic pathways significantly associated with PsA (pFDR<0.05). From these, the glycosaminoglycan (GAG) metabolism pathway was confirmed to be disease-specific after comparing the PsA cohort with the cohorts of patients with PsC and RA. Finally, we identified candidate drug targets in the GAG metabolism pathway as well as new PsA indications for approved drugs. CONCLUSION: These findings provide insights into the biological mechanisms that are specific for PsA and could contribute to develop more effective therapies

Functional-based networks analyzed in each enriched CD4+ T cell gene expression module.

<p><b>A</b>: Functional-based network obtained from the immunologically enriched M9 gene expression module. <b>B</b>: Functional-based network obtained from the immunologically enriched M12 gene expression module. The dimensions of each node (i.e. gene) are proportional to its DC value and its color is based on its BC value, ranging from green (lowest BC values) to red (highest BC values). The edge width is proportional to the strength of the functional association evidences between two genes. The edge betweenness determines the edge color, ranging from green (edges connecting nodes with the lowest BC values) to red (edges connecting nodes with the highest BC values).</p

Transcript Complexity Value analysis of RA risk genes.

<p>TCV from the RA CD4+ T cell and control LCLs analyzed in RA risk genes. <b>A</b>: JAK-STAT signaling pathway. <b>B</b>: T cell receptor signaling pathway. <b>C</b>: TNF signaling pathway. <b>D</b>: Cell adhesion pathway. <b>E</b>: Toll-like receptor signaling pathway. <b>F</b>: Antigen processing and presentation pathway. <b>G</b>: B cell development function pathway. The genes that are framed represent those genes showing significant genomic regulation profiles between RA CD4+ T cells and LCLs (P<0.05).</p