DNA variants (SNPs) that predispose to common traits often localize within noncoding regulatory elements such as enhancers. Moreover, loci identified by genome-wide association studies (GWAS) often contain multiple SNPs in linkage disequilibrium (LD), any of which may be causal. Thus, determining the effect of these multiple variant SNPs on target transcript levels has been a major challenge. Here, we provide evidence that for six common autoimmune disorders (rheumatoid arthritis, Crohn's disease, celiac disease, multiple sclerosis, lupus, and ulcerative colitis), the GWAS association arises from multiple polymorphisms in LD that map to clusters of enhancer elements active in the same cell type. This finding suggests a "multiple enhancer variant" hypothesis for common traits, where several variants in LD impact multiple enhancers and cooperatively affect gene expression. Using a novel method to delineate enhancer-gene interactions, we show that multiple enhancer variants within a given locus typically target the same gene. Using available data from HapMap and B lymphoblasts as a model system, we provide evidence at numerous loci that multiple enhancer variants cooperatively contribute to altered expression of their gene targets. The effects on target transcript levels tend to be modest and can be either gain- or loss-of-function. Additionally, the genes associated with multiple enhancer variants encode proteins that are often functionally related and enriched in common pathways. Overall, the multiple enhancer variant hypothesis offers a new paradigm by which noncoding variants can confer susceptibility to common traits.

Cancer is characterized by gene expression aberrations. Studies have largely focused on coding sequences and promoters, despite the fact that distal regulatory elements play a central role in controlling transcription patterns. Here we utilize the histone mark H3K4me1 to analyze gain and loss of enhancer activity genome wide in primary colon cancer lines relative to normal colon crypts. We identified thousands of variant enhancer loci (VELs) that comprise a signature that is robustly predictive of the in vivo colon cancer transcriptome. Furthermore, VELs are enriched in haplotype blocks containing colon cancer genetic risk variants, implicating these genomic regions in colon cancer pathogenesis. We propose that reproducible changes in the epigenome at enhancer elements drive a unique transcriptional program to promote colon carcinogenesis.

Gene enhancer elements are noncoding segments of DNA that play a central role in regulating transcriptional programs that control development, cell identity, and evolutionary processes. Recent studies have shown that noncoding single nucleotide polymorphisms (SNPs) that have been associated with risk for numerous common diseases through genome-wide association studies frequently lie in cell-type-specific enhancer elements. These enhancer variants probably influence transcriptional output, thereby offering a mechanistic basis to explain their association with risk for many common diseases. This review focuses on the identification and interpretation of disease-susceptibility variants that influence enhancer function. We discuss strategies for prioritizing the study of functional enhancer SNPs over those likely to be benign, review experimental and computational approaches to identifying the gene targets of enhancer variants, and highlight efforts to quantify the impact of enhancer variants on target transcript levels and cellular phenotypes. These studies are beginning to provide insights into the mechanistic basis of many common diseases, as well as into how we might translate this knowledge for improved disease diagnosis, prevention and treatments. Finally, we highlight five major challenges often associated with interpreting enhancer variants, and discuss recent technical advances that may help to surmount these challenges.

Chromatin interactions connect distal regulatory elements to target gene promoters guiding stimulus- and lineage-specific transcription. Few factors securing chromatin interactions have so far been identified. Here by integrating chromatin interaction maps with the large collection of transcription factor binding profiles provided by the ENCODE project, we demonstrate that the zinc-finger protein ZNF143 preferentially occupies anchors of chromatin interactions connecting promoters with distal regulatory elements. It binds directly to promoters and associates with lineage-specific chromatin interactions and gene expression. Silencing ZNF143 or modulating its DNA-binding affinity using single nucleotide polymorphisms (SNPs) as a surrogate of site-directed mutagenesis reveals the sequence dependency of chromatin interactions at gene promoters. We also find that chromatin interactions alone do not regulate gene expression. Together, our results identify ZNF143 as a novel chromatin-looping factor that contributes to the architectural foundation of the genome by providing sequence specificity at promoters connected with distal regulatory elements.

SUMMARY Naïve mouse embryonic stem cells (mESCs) and primed epiblast stem cells (mEpiSCs) represent successive snapshots of pluripotency during embryogenesis. Using transcriptomic and epigenomic mapping we show that a small fraction of transcripts are differentially expressed between mESCs and mEpiSCs and these genes show expected changes in chromatin at their promoters and enhancers. Unexpectedly, the cis-regulatory circuitry of genes that are expressed at identical levels between these cell states also differs dramatically. In mESCs, these genes are associated with dominant proximal enhancers and dormant distal enhancers, which we term seed enhancers. In mEpiSCs, the naïve-dominant enhancers are lost, and the seed enhancers take up primary transcriptional control. Seed enhancers have increased sequence conservation and show preferential usage in downstream somatic tissues, often expanding into super enhancers. We propose that seed enhancers ensure proper enhancer utilization and transcriptional fidelity as mammalian cells transition from naïve pluripotency to a somatic regulatory program.