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In the last 15 years Genome wide association studies (GWAS) have uncovered the genetic factors that contribute to disease risk for many disorders, yet the biological significance of many of these associations remain unclear. This is because about 90% of these variants are predicted to affect regulatory elements that are highly cell-type specific and can affect distal genes through chromatin interaction mechanisms and, therefore, understanding their role in disease is challenging. Previous studies have attempted to use chromatin conformation methods to describe the functional mechanism in disease associated loci. However, the majority of these studies have focused on cell lines derived from blood, which might not be the most relevant cell lines for dermatological conditions. Here, we generated HiChIP for H3K27ac, Hi-C and RNA-seq datasets from a keratinocyte and a skin-plaque derived CD8+ T cell line. We studied their active chromatin conformation with the aim to identify biological mechanisms that could be affected by variants associated with skin related diseases: psoriasis (Ps), psoriatic arthritis (PsA), systemic sclerosis (SSc), melanoma and atopic dermatitis. In our analysis we show that HiChIP interactions provide functional evidence for gene regulation by showing that enhancers linked to genes that respond to IFN-γ stimulation are strongly enriched for motifs for TFs related to the stimulation. We also show that by using chromatin conformation we can recall 53% of eQTLs identified by GTEx in skin. In addition to our datasets, we integrated public datasets for a B cell-like lymphoblastoid cell line and primary CD4+ T cells to expand our analysis to include GWAS variants associated with the aforementioned diseases likely to be mediated specifically by B cells and CD4+ T cells (such as in systemic sclerosis and melanoma). We then identified the numerous genes that interact with GWAS variants associated and show that these genes strongly enrich for pathways that are related to the trait studied. For example, the top enriched pathways for autoimmune conditions such as PsA and psoriasis included responses to cytokines and T cell regulation, whereas for melanoma they were related to replicative senescence. We show examples of how our analysis can inform changes in the current description of a few psoriasis associated risk loci. For example, the variant rs10794648, which had previously been assigned to IFNLR1, was linked to GRHL3 in our dataset, a gene essential in skin repair and development. This can indicate a renewed importance of skin related factors in the risk of disease. In conclusion, this study allows us to further characterize disease risk loci by using novel chromatin conformation techniques, which can help identify the genes that are putatively involved in disease and has the potential to identify therapeutic targets.

SUMMARY Morphogen gradients specify cell fates during development, with a classic example being the BMP gradient’s conserved role in embryonic dorsal-ventral axis patterning. Here we use quantitative imaging and computational modelling to determine how the BMP gradient is interpreted at single-cell resolution in the Drosophila embryo. We show that BMP signalling levels are decoded by modulating promoter occupancy, the time the promoter is active, predominantly through regulating the promoter activation rate. As a result, graded mRNA numbers are detected for BMP target genes in cells across their expression domains. Introducing a heterologous promoter into a BMP target gene changes burst amplitude but not promoter occupancy suggesting that, while the promoter sequence controls amplitude, occupancy depends on the amount of BMP signal decoded by the enhancer. We provide evidence that graded mRNA output is a general feature of morphogen gradient interpretation and discuss how this can impact on cell fate decisions.

Genome-wide association studies have identified genetic variation contributing to complex disease risk but assigning causal genes and mechanisms has been more challenging, as disease-associated variants are often found in distal regulatory regions with cell-type specific behaviours. Here, the simultaneous correlation of ATAC-seq, Hi-C, Capture Hi-C and nuclear RNA-seq data, in the same stimulated T-cells over 24 hours, allowed the assignment of functional enhancers to genes. We show how small magnitude changes in DNA interaction and activity dynamics are correlated with much larger changes to dynamics in gene expression and that the strongest correlations are observed within 200 kb of promoters. Using rheumatoid arthritis as an exemplar T-cell mediated disease, we demonstrate interactions of expression quantitative trait locus SNPs with target genes and confirm assigned genes or show complex interactions for 20% of disease associated loci. Finally, we confirm one of the putative causal genes using CRISPR/Cas9.