Orphanet Journal of Rare Diseases | Genome-wide association analysis identifies novel risk loci and heritability for sarcoidosis

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This study conducted a large-scale integrative analysis of genome-wide association studies (GWAS) across European, African, and East Asian populations, identifying 19 European and 2 African-specific risk loci for sarcoidosis for the first time in multi-ancestry cohorts, offering new insights into the genetic mechanisms of the disease.

 

Literature Overview

This article, titled 'Genome-wide association for sarcoidosis identifies novel risk loci and genetic heritability in African and European ancestries: a meta-analysis from the FinnGen, Million Veteran Program, UK Biobank, and Biobank Japan datasets', was published in the Orphanet Journal of Rare Diseases. It reviews and summarizes the genetic susceptibility of sarcoidosis, identifies multiple novel risk loci, and estimates heritability across different ancestral backgrounds. The study further explores gene set enrichment related to interferon gamma signaling and DNA methylation, providing a theoretical basis for functional validation and therapeutic targeting of sarcoidosis.

Background Knowledge

Sarcoidosis is a multisystem granulomatous disease characterized by significant clinical heterogeneity and racial disparities. Although previous studies have confirmed a strong association between the HLA class II gene region and the disease, identification of additional genetic risk loci remains limited. This study integrates public GWAS summary data from FinnGen, UK Biobank, Million Veteran Program, and Biobank Japan, marking the first genome-wide association study of sarcoidosis across multiple ancestral backgrounds. The study aims to identify novel risk loci, evaluate heritability differences across populations, and explore potential epigenetic mechanisms, offering insights into molecular mechanisms and precision medicine for sarcoidosis.

 

FUMA functional annotation tool used for multi-ancestry GWAS data integration analysis, enabling tissue expression and gene set enrichment analysis.

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Study Methods and Experiment

The study integrated GWAS summary data from four large biobanks (FinnGen r12, UK Biobank, Million Veteran Program, Biobank Japan) and performed cross-ancestry meta-analysis using a sample-size-based approach. Statistical integration was conducted using METAL, and heritability was assessed via LD Score regression. Functional annotation was completed through the FUMA GWAS platform, incorporating ANNOVAR and CADD scores for SNP functional prediction. Tissue expression and gene set enrichment analysis (GSEA) were performed using MAGMA, with MHC regions excluded to reduce linkage disequilibrium interference.

Key Findings and Perspectives

• 19 significant risk loci were identified in individuals of European ancestry (EUR), with 6 being newly reported.
• 2 risk loci were identified in African ancestry (AFR) populations, primarily from MVP data, but the signals were weak, suggesting limited sample size.
• Multi-ancestry meta-analysis identified 18 risk loci, with loci on chromosomes 1, 3, 10, and 12 being EUR-specific.
• Heritability (h2) in EUR populations was estimated at 0.25, and at 0.19 in AFR, indicating moderate genetic contribution to sarcoidosis.
• Tissue expression analysis in EUR showed significant enrichment in immune-related tissues such as whole blood, spleen, and lung.
• Gene set enrichment analysis revealed significant enrichment in IFNγ signaling, DNA methylation, and synaptonemal complex formation pathways in EUR and multi-ancestry analyses.
• Several non-MHC genes (e.g., IL23R, PLCL1, ANXA11, CD19, UBASH3A) were significantly associated with sarcoidosis, suggesting their potential roles in immune regulation.
• The study highlights the insufficient representation of African and East Asian populations, limiting the detection of ancestry-specific risk loci.

Significance and Future Directions

This study, through large-scale trans-ethnic GWAS meta-analysis, identifies sarcoidosis-related risk loci in multi-ancestry backgrounds for the first time, offering new genetic evidence for its immunological mechanisms. Future efforts should focus on expanding sample sizes in African and East Asian populations to improve resolution of genetic variation analysis and further validate the functional mechanisms of these risk loci. The study also suggests that epigenetic regulation, such as DNA methylation, may play a significant role in sarcoidosis pathogenesis, offering new insights for immunomodulatory therapies.

 

CADD score tool for evaluating the pathogenic potential of gene variants, assisting in the screening of SNPs with high functional impact.

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Conclusion

This study performed cross-ancestry integrated GWAS analysis on four large biobanks and identified multiple novel risk loci for sarcoidosis in European and African populations, while estimating heritability. The IFNγ signaling pathway and DNA methylation-related gene sets were significantly enriched in EUR and multi-ancestry analyses, suggesting a potential role of epigenetic mechanisms in sarcoidosis. Although fewer risk loci were identified in African populations, the findings emphasize the necessity of expanding research on non-European populations to enhance genetic resolution for the disease. This study provides new genetic clues for molecular mechanism and targeted therapy of sarcoidosis, laying the foundation for future multi-omics integrated analyses.

 

Andrea Ricci, Federica Andolfi, Daniele Sabbatini, Elena Corradini, and Stefania Cerri. Genome-wide association for sarcoidosis identifies novel risk loci and genetic heritability in African and European ancestries: a meta-analysis from the FinnGen, Million Veteran Program, UK Biobank, and Biobank Japan datasets. Orphanet Journal of Rare Diseases.