Chromatin accessibility variation provides insights into missing regulation underlying immune-mediated diseases

Area of Science:

• Genomics
• Genetic Epidemiology
• Molecular Biology

Background:

• Genome-wide association studies (GWAS) identify noncoding genetic loci linked to complex traits and diseases.
• Causal variants in these loci are presumed to have gene regulatory effects.
• However, few loci colocalize with expression quantitative trait loci (eQTLs), indicating a gap in understanding regulatory mechanisms.

Purpose of the Study:

• To investigate chromatin accessibility quantitative trait loci (caQTLs) in lymphoblastoid cell lines (LCLs) as a potential explanation for immune-mediated disease associations not explained by LCL eQTLs.
• To assess the contribution of statistical power and cell-type specificity to the 'missing regulation' phenomenon.

Main Methods:

• Comparison of the detection power between caQTLs and eQTLs in lymphoblastoid cell lines (LCLs).
• Analysis of the influence of distance from the transcription start site on QTL detection.
• Meta-analysis of LCL eQTL data with increased sample size.
• Surveying eQTLs across different immune cell types.

Main Results:

• caQTLs demonstrated greater detection power than eQTLs and were less sensitive to the distance from the transcription start site.
• Increasing sample size for LCL eQTLs revealed additional colocalizing loci, highlighting the role of statistical power.
• Examining eQTLs in other immune cell types identified further colocalizing loci, underscoring context specificity.

Conclusions:

• Both insufficient statistical power and the cell-type specificity of expression quantitative trait loci (eQTLs) contribute to the 'missing regulation' observed in genetic studies.
• Chromatin accessibility QTLs (caQTLs) offer a complementary approach to eQTLs for identifying regulatory variants associated with complex traits and diseases.
• Future research should consider diverse regulatory element assays and multiple cell types to fully capture the regulatory landscape of noncoding variants.