Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 4 uppsatser.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2001. / Härtill 4 uppsatser.

Gene expression quantitative trait loci (eQTL) mapping studies can provide mechanistic insights into the functions of disease-associated variants. However, many eQTLs are cell type and context specific. This is particularly relevant for immune cells, whose cellular function and behaviour can be substantially altered by external cues. Furthermore, understanding mechanisms behind eQTLs is hindered by the difficulty of identifying causal variants. We differentiated macrophages from induced pluripotent stem cells from 86 unrelated, healthy individuals derived as part of the Human Induced Pluripotent Stem Cells Initiative. We generated RNA-seq data from these cells in four experimental conditions: naïve, interferon- gamma (IFNɣ) treatment (18h), Salmonella infection (5h), and IFNγ treatment followed by Salmonella infection. We also measured chromatin accessibility with ATAC-seq in 31-42 individuals in the same four conditions. We detected gene expression QTLs (eQTLs) for 4326 genes, over 900 of which were condition-specific. We also detected a similar number of transcript ratio QTLs (trQTLs) that influenced mRNA processing and alternative splicing. Macrophage eQTLs and trQTLs were enriched for variants associated with Alzheimer’s disease, multiple autoimmune disorders and lipid traits. We also detected chromatin accessibility QTLs (caQTLs) for 14,602 accessible regions, including hundreds of long-range interactions. Joint analysis of eQTLs with caQTLs allowed us to greatly reduce the set of credible causal variants, often pinpointing to a single most likely variant. We found that caQTLs were less condition- specific than eQTLs and ~50% of the stimulation-specific eQTLs manifested on the chromatin level already in the naive cells. These observations might help to explain the discrepancy between strong enrichment of diseases associations in regulatory elements but only modest overlap with current eQTL studies, suggesting that many regulatory elements are in a ‘primed’ state waiting for an appropriate environmental signal before regulating gene expression.