Promoter Capture Hi-C Research Articles

Investigating the role of WT1 in Brugada syndrome pathophysiology

Abstract Background Brugada syndrome (BrS) is a heritable arrhythmic disorder presumably caused by conduction slowing in the right ventricular (RV) outflow tract (RVOT). A recent genome-wide association study found an association between common variants on chromosome 11 near WT1, tagged by the SNP rs72905083, and BrS susceptibility. Purpose To study whether WT1 affects cardiac conduction and could therefore represents the underlying association of the chr11 locus with BrS susceptibility. Methods We conducted in silico analyses of omics datasets to identify the likely causal gene at the chr11 BrS locus. Next, we conducted electrophysiological studies in heterozygous young adult (4 months old) Wt1-deficient (Wt1+/-) mice and wild-type littermates to explore the effect of Wt1 on cardiac conduction. To study the potential role of Wt1 in the setting of reduced conduction reserve, we compared aged Scn5a haploinsufficient mice (Scn5a+/-;Wt1+/+, 17 months) with littermates haploinsufficient for both Wt1 and Scn5a (Scn5a+/-;Wt1+/-). Optical mapping was performed in Langendorff-perfused hearts, where conduction was further challenged by acute ajmaline administration or by pacing at the effective refractory period (ERP). Transcriptomic analyses were conducted in Wt1+/- and wild-type mice by RNAseq of PCM1-sorted cardiomyocytes. Results Analysis of omics datasets uncovered WT1 as the likely causal gene since WT1 was the closest gene to, and in fact overlapped, the BrS-associated region; promoter capture Hi-C data in human tissue showed chromatin contact between the promoter of WT1 and the associated region; and H3K27ac ChIP-seq signals (i.e. enhancer activity) of putative cardiac enhancers located within the associated region were correlated with WT1 transcript abundance across multiple tissues (Z-score = 4.32, p=1.57e-05). No differences were observed in ECG parameters or optically mapped epicardial conduction between Wt1+/- mice and wild-type littermates. However, comparison of aged Scn5a+/-;Wt1+/- and Scn5a+/-; Wt1+/+ hearts, in the setting of acute ajmaline challenge or pacing at the ERP, showed faster conduction in RV/RVOT in the presence of Wt1 haploinsufficiency (genotype effect: p=0.057 and p=0.041 for RV and RVOT epicardial conduction, respectively, during ajmaline challenge; p=0.034 for RV epicardial conduction during pacing at ERP). RNAseq of RV/RVOT cardiomyocytes revealed higher Scn5a expression in Wt1+/- vs wild-type (p=0.006). Conclusion We identified WT1 as the gene that most likely underlies the effect of the chr11 BrS susceptibility locus. Functional data revealed protective effects of reduced Wt1 expression in the setting of reduced conduction reserve. Transcriptomic data suggest that this occurs through a transcriptional effect on Scn5a expression.

Three-dimensional chromatin mapping of sensory neurons reveals that promoter–enhancer looping is required for axonal regeneration

The in vivo three-dimensional genomic architecture of adult mature neurons at homeostasis and after medically relevant perturbations such as axonal injury remains elusive. Here, we address this knowledge gap by mapping the three-dimensional chromatin architecture and gene expression program at homeostasis and after sciatic nerve injury in wild-type and cohesin-deficient mouse sensory dorsal root ganglia neurons via combinatorial Hi-C, promoter-capture Hi-C, CUT&Tag for H3K27ac and RNA-seq. We find that genes involved in axonal regeneration form long-range, complex chromatin loops, and that cohesin is required for the full induction of the regenerative transcriptional program. Importantly, loss of cohesin results in disruption of chromatin architecture and severely impaired nerve regeneration. Complex enhancer-promoter loops are also enriched in the human fetal cortical plate, where the axonal growth potential is highest, and are lost in mature adult neurons. Together, these data provide an original three-dimensional chromatin map of adult sensory neurons in vivo and demonstrate a role for cohesin-dependent long-range promoter interactions in nerve regeneration.

Enhlink infers distal and context-specific enhancer–promoter linkages

Enhlink is a computational tool for scATAC-seq data analysis, facilitating precise interrogation of enhancer function at the single-cell level. It employs an ensemble approach incorporating technical and biological covariates to infer condition-specific regulatory DNA linkages. Enhlink can integrate multi-omic data for enhanced specificity, when available. Evaluation with simulated and real data, including multi-omic datasets from the mouse striatum and novel promoter capture Hi-C data, demonstrate that Enhlink outperfoms alternative methods. Coupled with eQTL analysis, it identified a putative super-enhancer in striatal neurons. Overall, Enhlink offers accuracy, power, and potential for revealing novel biological insights in gene regulation.

MethNet: a robust approach to identify regulatory hubs and their distal targets from cancer data

Aberrations in the capacity of DNA/chromatin modifiers and transcription factors to bind non-coding regions can lead to changes in gene regulation and impact disease phenotypes. However, identifying distal regulatory elements and connecting them with their target genes remains challenging. Here, we present MethNet, a pipeline that integrates large-scale DNA methylation and gene expression data across multiple cancers, to uncover cis regulatory elements (CREs) in a 1 Mb region around every promoter in the genome. MethNet identifies clusters of highly ranked CREs, referred to as ‘hubs’, which contribute to the regulation of multiple genes and significantly affect patient survival. Promoter-capture Hi-C confirmed that highly ranked associations involve physical interactions between CREs and their gene targets, and CRISPR interference based single-cell RNA Perturb-seq validated the functional impact of CREs. Thus, MethNet-identified CREs represent a valuable resource for unraveling complex mechanisms underlying gene expression, and for prioritizing the verification of predicted non-coding disease hotspots.

Integrative Multi-omics Analysis Identifies Genetic Variants Contributing to Non-syndromic Cleft Lip with or without Cleft Palate.

To provide novel insights into the aetiology of non-syndromic cleft lip with or without cleft palate (NSCL/P) by integrating multi-omics data and exploring susceptibility genes associated with NSCL/P. A two-stage genome-wide association study (GWAS) of NSCL/P was performed, involving a total of 1,069 cases and 1,724 controls. Using promoter capture Hi-C (pCHi-C) datasets in human embryonic stem cells (hESC) and chromatin immunoprecipitation sequencing (ChIP-seq) in craniofacial tissues, we filtered out single nucleotide polymorphisms (SNPs) with active cis-regulation and their target genes. Additionally, we employed expression quantitative trait loci (eQTL) analysis to identify candidate genes. Thirteen SNPs were identified as cis-regulation units associated with the risk of NSCL/P. Five of these were proven to be active in chromatin states in early human craniofacial development (rs7218002: odds ratio [OR] 1.50, P = 8.14E-08; rs835367: OR 0.78, P = 3.48E- 05; rs77022994: OR 0.55, P = 1.05E-04; rs961470: OR 0.73, P = 1.38E-04; rs17314727: OR 0.73, P = 1.85E-04). Additionally, pCHi-C and eQTL analysis prioritised three candidate genes (rs7218002: NTN1, rs835367: FGGY, LINC01135). NTN1 and FGGY were expressed in mouse orofacial development. Deficiencies in NTN1, FGGY and LINC01135 were associated with cleft palate and cleft lip, abnormal facial shape and bifid uvula, and abnormality of the face, respectively. Our study identified five SNPs (rs7218002, rs835367, rs77022994, rs961470 and rs17314727) and three susceptibility genes (NTN1, FGGY and LINC01135) associated with NSCL/P. These findings contribute to a better understanding of the genetic factors involved.

Abstract 143: Molecular profiling of tumor-initiation events in rhabdomyosarcoma uncovers mitochondrial vulnerabilities

Abstract Background: Alveolar Rhabdomyosarcoma (ARMS) is a very aggressive soft tissue tumor affecting children and adolescents. It is found that pediatric patients with RMS harboring chimeric PAX fusion transcription factors (TFs) exhibit a greater incidence of tumor relapse, metastasis, and poor survival outcome, thereby underscoring the urgent need to develop effective therapies to treat this subtype of childhood cancer. Methods: We generated a novel ARMS model by stable transduction of myogenic progenitor cells with a cassette encoding the exact PAX3/7-FOXO1 fusion protein found in ARMS tumors. We analyzed genome-wide expression levels with RNA-seq and utilized Cut&Run to map the binding sites of PAX3/7-FOXO1, active histone marks, enhancers, and super-enhancers in our novel model. Hi-C and promoter capture HiC (pCHiC) were also performed to generate 3D chromatin conformation maps in cells expressing the oncogenic TFs. We compared these data with analogous datasets from orthotopic patient-derived xenografts (O-PDXs) of PAX3/7-FOXO1 fusion-positive ARMS tumors from St. Jude and established ARMS cell lines to validate whether our model system recapitulates ARMS tumors. CRISPRi was performed to silence key targets in two representative ARMS cell lines and proliferation was scored after silencing. Next, we found that ARMS tumors displayed anomalies in mitochondrial mass and numbers, metabolic parameters, and membrane potential by performing TEM, Seahorse assays, and FACS-based TMRM and mitotracker Red dye uptake in a panel of ARMS cells and PDX samples. We performed cell viability and colony forming assays in ARMS cells treated with single drugs and combinations of drugs targeting FGFR4 and mitochondrial metabolism. Results: Our data provide evidence to support muscle progenitors as potential cells-of-origin for ARMS. We showed that rewiring of chromatin architecture mediated by PAX3/7-FOXO1 TFs is evident across established cell lines, primary tumors as well as O-PDXs. By integrating PAX3/7-FOXO1 binding, RNA-seq, and pCHiC data, we identified key promoter-enhancer (P-En) interactions that are erased or established de novo at multiple loci of master TFs like MYOD, MYOG and MYCN. We also identified key regulators of proliferation, including FGFR4, and mitochondrial function that are essential for tumor growth and invasiveness. Our data indicated aberrant and enhanced mitochondrial metabolism in ARMS as well as selective sensitivity to mitochondrial inhibitors in RMS cells. Administration of these inhibitors preferentially inhibited cell viability and clonogenicity in ARMS, and prompted a pre-clinical phase II study to test these inhibitors at St. Jude Research Hospital. Conclusion: We present a novel treatment strategy leveraging the mitochondrial dependencies of fusion positive PAX-driven tumors which can be exploited for precision therapy in high-risk ARMS. Citation Format: Bhargab Kalita, Gerard Martinez-Cebrian, Justina McEvoy, Brittney Gordon, Kaley Blankenship, Asa Karlstorm, Elizabeth Stewart, Michael Dyer, Brian Dynlacht. Molecular profiling of tumor-initiation events in rhabdomyosarcoma uncovers mitochondrial vulnerabilities [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 143.

Abstract 2850: Noncoding regulatory mutations as driving event for the oncogenic core regulatory circuitries of neuroblastoma

Abstract Background and Aim: Neuroblastoma (NB) is the most aggressive solid tumor of infancy and arises from neural-crest-derived progenitor cells. It is composed by cell types reflecting developmental stages of the adrenergic lineage: mesenchymal (MES) and adrenergic (ADRN) cell types. These cell identities result from the activity of NB specific Core Regulatory Circuitries (CRCs), transcription factor (TF) sets that co-occupy regulatory regions together impacting the expression of their own genes and those of lineage-specific ones governing cell state transitions and cellular identities. Our hypothesis is that noncoding somatic single nucleotide variants (SNVs) located in NB CRCs TF binding sites (TFBSs) underlie NB CRCs activity, affecting cellular differentiation and promoting tumor onset. We aim to investigate such pattern of regulatory elements and identify putative driver SNVs, exploring their role and characterizing their action mechanism. Methods: Transcriptionally active TFBSs (aTFBSs) bound by ADRN CRC TFs (GATA3, HAND2, ISL1, TBX2, MYCN, PHOX2B, ASCL1 and LMO1) were identified integrating 27 ChIP-seq and 11 ATAC-seq experiments in 6 NB ADRN cell lines (SKNBE2C, Kelly, NGP, COGN415, LAN5 and NB1643). In particular, aTFBSs were defined as ChIP-seq peaks overlapping ATAC-seq signals in the same cell line. SNVs from 317 NB whole genomes were mapped on aTFBSs and the enrichment of mutations in core regions respect to flanking ones was tested using Fisher test. Observed mutation rate in aTFBSs was compared with background mutation rate due to local sequence context. SNVs in mutated aTFBSs were selected and their impact on TF binding affinity was evaluated with FABIAN-variant and motifbreakR tools. aTFBSs target-genes were identified through promoter capture HiC (CHiC) in ADRN NB cells (SKNBE2C and SHSY5Y). Results: We found a significant (FDR < 0.05) mutation enrichment in aTFBSs of ISL1, PHOX2B, TBX2, GATA3 and MYCN, suggesting a common somatic mutation burden for a subset of ADRN CRC TFBSs in ADRN NB cells. Starting from 839 SNVs falling in significantly mutated aTFBSs, we selected 269 mutations impacting the binding of ADRN CRC TFs. This mutations subset mapped in aTFBSs interacting with genes that significantly enriched pathways involved in neuronal development and migration (FDR < 0.05), thus suggesting their possible role in affecting cell identity definition. As an example, chr6:137753475:G>T mapped in aTFBSs interacting with the promoter of OLIG3, which takes part in neuronal differentiation. Interestingly, chr6:137753475:G>T was predicted to break the binding to ISL1 (FABIAN score: -0.24), a key regulator of ADRN CRC. Conclusions: These results demonstrate that somatic noncoding SNVs can act synergistically to promote NB onset, affecting CRCs activity and, in turn, the normal cell identity definition. Citation Format: Mario Capasso, Vincenzo Aievola, Vito Alessandro Lasorsa, Annalaura Montella, Ferdinando Bonfiglio, Marianna Avitabile, Teresa Maiorino, Matilde Tirelli, Giuseppe D'Alterio, Matthias Fischer, Frank Westermann, Achille Iolascon. Noncoding regulatory mutations as driving event for the oncogenic core regulatory circuitries of neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2850.

Single-cell multi-ome regression models identify functional and disease-associated enhancers and enable chromatin potential analysis

We present a gene-level regulatory model, single-cell ATAC + RNA linking (SCARlink), which predicts single-cell gene expression and links enhancers to target genes using multi-ome (scRNA-seq and scATAC–seq co-assay) sequencing data. The approach uses regularized Poisson regression on tile-level accessibility data to jointly model all regulatory effects at a gene locus, avoiding the limitations of pairwise gene–peak correlations and dependence on peak calling. SCARlink outperformed existing gene scoring methods for imputing gene expression from chromatin accessibility across high-coverage multi-ome datasets while giving comparable to improved performance on low-coverage datasets. Shapley value analysis on trained models identified cell-type-specific gene enhancers that are validated by promoter capture Hi-C and are 11× to 15× and 5× to 12× enriched in fine-mapped eQTLs and fine-mapped genome-wide association study (GWAS) variants, respectively. We further show that SCARlink-predicted and observed gene expression vectors provide a robust way to compute a chromatin potential vector field to enable developmental trajectory analysis.

Abstract B057: Oncogenic Foxl2 directs enhancer reprogramming and changes in 3D genome structure in ovarian granulosa cell tumors

Abstract Background: Adult-type granulosa cell tumors (aGCTs) are a rare monogenic disease. Nearly all aGCTs carry a missense point mutation in the Forkhead domain containing FOXL2 (Foxl2 p.C134W) transcription factor, but the oncogenic mechanism of this mutation is unknown. Other Forkhead family transcription factors have well-described “pioneer” activity, binding to compacted, nucleosome-bound DNA and increasing accessibility for other regulatory proteins. Objectives: To investigate if oncogenic Foxl2-C134W has pioneering activity and if mutant Foxl2 operates its oncogenic activity through enhancer reprogramming. Methods: CRISPR/Cas9 editing was used to generate isogenic granulosa cell tumor cells lacking either the FOXL2 wild-type allele (single knock-out; SKO) or both the mutant and wild-type FOXL2 alleles (double knock-out; DKO). ATAC-Seq and endogenous Foxl2 ChIP-Seq were performed on these isogenic lines to determine the differential chromatin accessibility at Foxl2-bound regulatory regions across genotypes. Promoter capture HiC was performed using a bespoke genome-wide hybrid capture probe set, CHiCAGO was used to identify significant HiC interactions, and an activity-by-contact model was constructed to identify enhancer elements bound by endogenous Foxl2-C134W and determine their target promoter contact frequency (promoter capture HiC) and enhancer activity (geometric mean of H3K27ac and ATACseq signal. Results: Endogenous ChIP-seq of Foxl2-C134W from the SKO cell line identified 1147 high-confidence peaks. De novo motif discovery identified the canonical Foxl2 binding motif (TGTTTACATT, P = 1.4 × 10−7) in 44.9% of peaks, as well as a novel variant motif (TGTTTTGTCT, P = 6.7 × 10−15) in 68.5% of peaks. Median chromatin accessibility at Foxl2-C134W peak regions, as measured by ATAC-seq, was significantly decreased in the DKO cells compared to either SKO or parental cell lines (P < 2 × 10-16 for both comparisons). Decreased chromatin accessibility at Foxl2-C134W ChIP-seq peaks in the DKO cells was driven by peaks containing the novel variant Foxl2 binding motif. Promoter capture HiC through activity-by-contact model identified promoter-enhancer interactions lost in the DKO cell line involving several genes, including ADAMTS5, FOXF2, and PRICKLE1 (adjusted P < 0.05). Conclusion: Foxl2-C134W exhibits “pioneering” activity, increasing chromatin accessibility at key gene regulatory elements with associated re-programming of promoter-enhancer interactions. The oncogenic mechanism of Foxl2-C134W in granulosa cell tumors may involve changes in DNA binding specificity, re-directing this pioneering function to sites containing a novel variant Foxl2 binding motif. Citation Format: Veena K. Vuttaradhi, Eleonora Khlebus, Thomas Welte, Barrett Lawson, Robert Tyler Hillman. Oncogenic Foxl2 directs enhancer reprogramming and changes in 3D genome structure in ovarian granulosa cell tumors [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr B057.

The Transcriptional Landscape of Ph+B-ALL Is Orchestrated By Long-Range Enhancer-Promoter Interactions and the Coordinated Action of Phosphorylation-Dependent and Phosphorylation-Independent Transcription Factors

Background and Hypothesis: B-cell precursor leukaemia (B-ALL) subtypes can be distinguished by their initiating genetic lesions. Likewise, each subtype exhibits a unique transcriptional program that drives the malignancy and defines the subtype. This often relates to the initiating genetic alteration that affects genes encoding transcription factors (TFs). However, for B-ALLs not driven by TF alterations it is less clear how the transcriptional program is established. Ph+B-ALL is a historically poor prognosis B-ALL driven by the BCR::ABL1 oncogene, a constitutive tyrosine kinase that activates its targets via phosphorylation. We hypothesised that BCR::ABL1 initiates the transcriptional signature of Ph+B-ALL cells by a two-step mechanism involving phosphorylation-activatable TFs, which then induce the expression of additional TFs that consecutively establish the Ph+B-ALL-defining transcriptome. As gene expression is often modulated by cis-regulatory elements such as enhancers, we further speculated that BCR::ABL1 reprograms the enhancer landscape to promote the transcriptional changes that define Ph+B-ALL. Results: Using an in vitro model of BCR::ABL1-induced transformation of murine B-cell precursors, we show that transcriptional deregulation by BCR::ABL1 is a continuous process evolving until full transformation is established. Only a minority of induced transcriptional changes occur immediately upon BCR::ABL1 expression (3 days), while most affected genes require an extended period of BCR::ABL1 to become deregulated. Furthermore, less than half of deregulated genes in murine Ph+B-ALL and less than 10% of human Ph+B-ALL-defining genes were sensitive to 24h BCR::ABL1 inhibition, suggesting an involvement of phosphorylation-dependent and phosphorylation-independent TFs. TF motif enrichment analysis of active chromatin in human and mouse Ph+B-ALL cells indicated the phosphorylation-dependent TF STAT5 and the phosphorylation-independent TF ETV5 as main mediators. Degron-induced rapid degradation of each TF in Ph+B-ALL cells confirmed their unique and overlapping roles and coordinated action. In parallel to gene expression changes, Ph+B-ALL cells further acquire changes in their enhancer signatures defined by H3K27ac+ at non-promoter regions, and these enhancer signatures can be efficiently used to distinguish Ph+B-ALL from other B-ALL subtypes. Analysis of chromatin interactions of these active enhancers with respective active promoters by Promoter-Capture Hi-C (PCHI-C) in combination with H3K27ac-ChIP-Seq showed that most active genes in Ph+B-ALL cells physically interact with an enhancer, including many genes described to be essential for Ph+B-ALL cells, such as CCND2, BCL2, BCL2L1, and ETV5. Using PCHI-C and H3K27ac-HiChIP we further show that, like gene expression and enhancer signatures, physical contacts of promoters and enhancers can be efficiently used to identify Ph+B-ALL cells and distinguish them from other B-ALLs such as KMT2A-rearranged B-ALL. Subtype-specific chromatin interactions that allow this differentiation directly relate to the transcriptional programs that define the respective B-ALL subtype. Conclusion: We describe here the molecular details of how signals from an oncogenic tyrosine kinase become converted into changes in gene expression that define the B-lineage leukaemia subtype Ph+B-ALL. Our work highlights the complexity of these changes by acknowledging the role of gene regulatory elements/enhancers in this process and further describe for the first time that B-ALL subtypes can be distinguished by their enhancer usage and promoter-enhancer interactions. Uncovering the precise enhancer regions for the genes deregulated in Ph+B-ALL and the TFs recruited to them may open new windows for therapeutic intervention.

Cellular reprogramming is driven by widespread rewiring of promoter-enhancer interactions

BackgroundLong-range interactions between promoters and cis-regulatory elements, such as enhancers, play critical roles in gene regulation. However, the role of three-dimensional (3D) chromatin structure in orchestrating changes in transcriptional regulation during direct cell reprogramming is not fully understood.ResultsHere, we performed integrated analyses of chromosomal architecture, epigenetics, and gene expression using Hi-C, promoter Capture Hi-C (PCHi-C), ChIP-seq, and RNA-seq during trans-differentiation of Pre-B cells into macrophages with a β-estradiol inducible C/EBPαER transgene. Within 1h of β-estradiol induction, C/EBPα translocated from the cytoplasm to the nucleus, binding to thousands of promoters and putative regulatory elements, resulting in the downregulation of Pre-B cell-specific genes and induction of macrophage-specific genes. Hi-C results were remarkably consistent throughout trans-differentiation, revealing only a small number of TAD boundary location changes, and A/B compartment switches despite significant changes in the expression of thousands of genes. PCHi-C revealed widespread changes in promoter-anchored loops with decreased interactions in parallel with decreased gene expression, and new and increased promoter-anchored interactions in parallel with increased expression of macrophage-specific genes.ConclusionsOverall, our data demonstrate that C/EBPα-induced trans-differentiation involves few changes in genome architecture at the level of TADs and A/B compartments, in contrast with widespread reorganization of thousands of promoter-anchored loops in association with changes in gene expression and cell identity.

Integration of genetic fine-mapping and multi-omics data reveals candidate effector genes for hypertension

Genome-wide association studies of blood pressure (BP) have identified >1,000 loci, but the effector genes and biological pathways at these loci are mostly unknown. Using published association summary statistics, we conducted annotation-informed fine-mapping incorporating tissue-specific chromatin segmentation and colocalization to identify causal variants and candidate effector genes for systolic BP, diastolic BP, and pulse pressure. We observed 532 distinct signals associated with ≥2 BP traits and 84 with all three. For >20% of signals, a single variant accounted for >75% posterior probability, 65 were missense variants in known (SLC39A8, ADRB2, and DBH) and previously unreported BP candidate genes (NRIP1 and MMP14). In disease-relevant tissues, we colocalized >80 and >400 distinct signals for each BP trait with cis-eQTLs and regulatory regions from promoter capture Hi-C, respectively. Integrating mouse, human disorder, gene expression and tissue abundance data, and literature review, we provide consolidated evidence for 436 BP candidate genes for future functional validation and discover several potential drug targets.

High-throughput identification of regulatory elements and functional assays to uncover susceptibility genes for nasopharyngeal carcinoma

Large-scale genetic association studies have identified multiple susceptibility loci for nasopharyngeal carcinoma (NPC), but the underlying biological mechanisms remain to be explored. To gain insights into the genetic etiology of NPC, we conducted a follow-up study encompassing 6,907 cases and 10,472 controls and identified two additional NPC susceptibility loci, 9q22.33 (rs1867277; OR= 0.74, 95% CI= 0.68-0.81, p= 3.08×10-11) and 17q12 (rs226241; OR= 1.42, 95% CI= 1.26-1.60, p= 1.62×10-8). The two additional loci, together with two previously reported genome-wide significant loci, 5p15.33 and 9p21.3, were investigated by high-throughput sequencing for chromatin accessibility, histone modification, and promoter capture Hi-C (PCHi-C) profiling. Using luciferase reporter assays and CRISPR interference (CRISPRi) to validate the functional profiling, we identified PHF2 at locus 9q22.33 as a susceptibility gene. PHF2 encodes a histone demethylase and acts as a tumor suppressor. The risk alleles of the functional SNPs reduced the expression of the target gene PHF2 by inhibiting the enhancer activity of its long-range (4.3 Mb) cis-regulatory element, which promoted proliferation of NPC cells. In addition, we identified CDKN2B-AS1 as a susceptibility gene at locus 9p21.3, and the NPC risk allele of the functional SNP rs2069418 promoted the expression of CDKN2B-AS1 by increasing its enhancer activity. The overexpression of CDKN2B-AS1 facilitated proliferation of NPC cells. In summary, we identified functional SNPs and NPC susceptibility genes, which provides additional explanations for the genetic association signals and helps to uncover the underlying genetic etiology of NPC development.

RELA governs a network of islet-specific metabolic genes necessary for beta cell function

Aims/hypothesisNF-κB activation unites metabolic and inflammatory responses in many diseases yet less is known about the role that NF-κB plays in normal metabolism. In this study we investigated how RELA impacts the beta cell transcriptional landscape and provides network control over glucoregulation.MethodsWe generated novel mouse lines harbouring beta cell-specific deletion of either the Rela gene, encoding the canonical NF-κB transcription factor p65 (βp65KO mice), or the Ikbkg gene, encoding the NF-κB essential modulator NEMO (βNEMOKO mice), as well as βA20Tg mice that carry beta cell-specific and forced transgenic expression of the NF-κB-negative regulator gene Tnfaip3, which encodes the A20 protein. Mouse studies were complemented by bioinformatics analysis of human islet chromatin accessibility (assay for transposase-accessible chromatin with sequencing [ATAC-seq]), promoter capture Hi-C (pcHi-C) and p65 binding (chromatin immunoprecipitation–sequencing [ChIP-seq]) data to investigate genome-wide control of the human beta cell metabolic programme.ResultsRela deficiency resulted in complete loss of stimulus-dependent inflammatory gene upregulation, consistent with its known role in governing inflammation. However, Rela deletion also rendered mice glucose intolerant because of functional loss of insulin secretion. Glucose intolerance was intrinsic to beta cells as βp65KO islets failed to secrete insulin ex vivo in response to a glucose challenge and were unable to restore metabolic control when transplanted into secondary chemical-induced hyperglycaemic recipients. Maintenance of glucose tolerance required Rela but was independent of classical NF-κB inflammatory cascades, as blocking NF-κB signalling in vivo by beta cell knockout of Ikbkg (NEMO), or beta cell overexpression of Tnfaip3 (A20), did not cause severe glucose intolerance. Thus, basal p65 activity has an essential and islet-intrinsic role in maintaining normal glucose homeostasis. Genome-wide bioinformatic mapping revealed the presence of p65 binding sites in the promoter regions of specific metabolic genes and in the majority of islet enhancer hubs (~70% of ~1300 hubs), which are responsible for shaping beta cell type-specific gene expression programmes. Indeed, the islet-specific metabolic genes Slc2a2, Capn9 and Pfkm identified within the large network of islet enhancer hub genes showed dysregulated expression in βp65KO islets.Conclusions/interpretationThese data demonstrate an unappreciated role for RELA as a regulator of islet-specific transcriptional programmes necessary for the maintenance of healthy glucose metabolism. These findings have clinical implications for the use of anti-inflammatories, which influence NF-κB activation and are associated with diabetes.Graphical

A meta-analysis of genome-wide association studies of childhood wheezing phenotypes identifies ANXA1 as a susceptibility locus for persistent wheezing.

Many genes associated with asthma explain only a fraction of its heritability. Most genome-wide association studies (GWASs) used a broad definition of 'doctor-diagnosed asthma', thereby diluting genetic signals by not considering asthma heterogeneity. The objective of our study was to identify genetic associates of childhood wheezing phenotypes. We conducted a novel multivariate GWAS meta-analysis of wheezing phenotypes jointly derived using unbiased analysis of data collected from birth to 18 years in 9568 individuals from five UK birth cohorts. Forty-four independent SNPs were associated with early-onset persistent, 25 with pre-school remitting, 33 with mid-childhood remitting, and 32 with late-onset wheeze. We identified a novel locus on chr9q21.13 (close to annexin 1 [ANXA1], p<6.7 × 10-9), associated exclusively with early-onset persistent wheeze. We identified rs75260654 as the most likely causative single nucleotide polymorphism (SNP) using Promoter Capture Hi-C loops, and then showed that the risk allele (T) confers a reduction in ANXA1 expression. Finally, in a murine model of house dust mite (HDM)-induced allergic airway disease, we demonstrated that anxa1 protein expression increased and anxa1 mRNA was significantly induced in lung tissue following HDM exposure. Using anxa1-/- deficient mice, we showed that loss of anxa1 results in heightened airway hyperreactivity and Th2 inflammation upon allergen challenge. Targeting this pathway in persistent disease may represent an exciting therapeutic prospect. UK Medical Research Council Programme Grant MR/S025340/1 and the Wellcome Trust Strategic Award (108818/15/Z) provided most of the funding for this study.

OpenXGR: a web-server update for genomic summary data interpretation.

How to effectively convert genomic summary data into downstream knowledge discovery represents a major challenge in human genomics research. To address this challenge, we have developed efficient and effective approaches and tools. Extending our previously established software tools, we here introduce OpenXGR (http://www.openxgr.com), a newly designed web server that offers almost real-time enrichment and subnetwork analyses for a user-input list of genes, SNPsor genomic regions. It achieves so through leveraging ontologies, networks, and functional genomic datasets (such as promoter capture Hi-C, e/pQTLand enhancer-gene maps for linking SNPs or genomic regions to candidate genes). Six analysers are provided, each doing specific interpretations tailored to genomic summary data at various levels. Three enrichment analysers are designed to identify ontology terms enriched for input genes, as well as genes linked from input SNPs or genomic regions. Three subnetwork analysers allow users to identify gene subnetworks from input gene-, SNP-or genomic region-level summary data. With a step-by-step user manual, OpenXGR provides a user-friendly and all-in-one platform for interpreting summary data on the human genome, enabling more integrated and effective knowledge discovery.

Abstract 159: Palmitic Acid Alters Enhancers And Super Enhancers Near Inflammatory And Efferocytosis-associated Genes In Human Monocytes

Background: Elevated free fatty acids (FFA) like palmitic acid (PA) are associated with inflammatory cardiometabolic disorders like diabetes and atherosclerosis. FFA induced dysregulated gene expression in monocytes plays important roles in inflammation, but the epigenetic mechanisms involved are unclear. Here we examined PA induced alterations in enhancer and super-enhancer (E/SE) repertoires to elucidate epigenetic mechanisms of inflammatory gene regulation in monocyte dysfunction. Methods: Human CD14 + monocytes from healthy volunteers were treated with PA (200 μM, 24 h) or vehicle (0.2% BSA). ChIP-seq with histone-H3K27ac was performed to identify Es/SEs and RNA-seq to analyze gene expression genome-wide. Publicly available Genomic Regions Enrichment of Annotations Tool, and datasets from promoter capture Hi-C (PCHiC) and GWAS on diabetes, obesity and BMI were used to analyze functions/disease relevance of Es/SEs. ChIP/RT-qPCRs were used to validate ChIP-/RNA-seq results. Functions of SEs were determined using JQ1 (SE/BET bromodomain inhibitor). Results: ChIP-seq results showed PA extensively dysregulated Es/SEs in CD14 + monocytes vs. vehicle control. PA-regulated Es/SEs showed enrichment of immune system related processes, differentiation, and cytokine production. RNA-seq showed significant correlations between dysregulated enhancers and differential expression of nearby genes. These genes were also altered in adipose tissue macrophages from high fat fed mice, and bone marrow derived macrophages from type2 diabetic db/db mice and Apoe -/- mice with accelerated atherosclerosis. Differentially regulated Es/SEs harbored SNPs associated with diabetes, obesity, and BMI. PCHiC revealed interactions between Es/SEs and promoters of key genes associated with efferocytosis ( MERTK ), metabolism ( OSBPL8 ) and inflammation ( IRAK2, CSF2 and RIPK2 ). Changes in gene expression and H3K27ac at Es/SEs were validated. Treatment with JQ1 reversed PA-induced inflammatory genes in monocytes. Conclusions: PA treatment dysregulated Es/SEs involved in key monocyte functions including efferocytosis, inflammation and metabolism. Targeting such epigenetic mechanisms could be beneficial in the treatment of cardiometabolic diseases.

P152 Allele-associated chromatin interactions in primary immune cells uncover mechanisms of gene regulation

Abstract Background/Aims Genome-wide association studies studies have identified many genetic variants associated with the risk of developing common rheumatological conditions. These variants primarily affect regulatory elements of the genome which can affect the expression of genes located far away from their genomic location through chromatin interaction mechanisms. Furthermore, common genetic variants have been associated with specific changes in chromatin interactions in cell lines. Studying chromatin interactions can improve our understanding of these diseases. Here, we aim to study chromatin interactions and how they are affected by genetic variation in primary immune cells that are relevant for rheumatological conditions. Methods We generated promoter Capture Hi-C (pCHi-C) data for primary CD4+ T cells and CD14+ monocytes isolated from peripheral blood of 10 systemic sclerosis patients and 5 healthy controls. We developed a new computational pipeline to explore how genetic variation affects chromatin interactions. Briefly, genotypes were called from the pCHi-C data using a modified GLIMPSE pipeline. Genotypes were phased using the integrated phasing pipeline which combined population haplotype information with the pCHi-C data. Reads were then assigned to the correct allele using SNPsplit and assigned to chromatin loops (CHiCAGO score &amp;gt; 5). A test for allelic imbalance was carried out using a binomial test, and results were consolidated using Fisher’s method. Results We identified 171 and 139 allele-associated loops (FDR &amp;lt; 0.05) in CD4+ T cells and CD14+ monocytes respectively. These interactions are cell-type specific and highly associated with expression quantitative trait loci (eQTLs). We found that 80% of the variants involved in allele-associated loops were eQTLs for at least one gene. These interactions link to the promoters of 62 and 57 distal genes in CD4+ T cells and CD14+ monocytes respectively. Of these, 38 and 31 respectively were also eQTL for those genes. Many of these allele-associated interactions affect genomic regions that are highly significant for the function of these cell populations. For example, a region with variants affecting T cell-specific chromatin interactions is the TRAF3IP3/IRF6/UTP25 locus. In this region there are separate groups of variants which affect gene expression with a complex mechanism. A group of variants overlapping the UTP25 promoter increases interaction strength with the TRAF3IP3 and IRF6 gene bodies. Interestingly, these are also associated with an increase in UTP25 expression but a decrease in TRAF3IP3 and IRF6 expression. Another group of variants located near the IRF6 promoter is associated with increased interactions with the UTP25 promoter. In contrast, these variants are associated with a reduction of UTP25 expression but an increase in TRAF3IP3 and IRF6 expression. Conclusion We created a new pipeline that allows the identification of allele-associated chromatin interactions in primary cells. These new data will be helpful in uncovering mechanisms of gene regulation in loci highly significant to autoimmune conditions. Disclosure D. González-Serna: None. C. Shi: None. M. Kerick: None. J. Hankinson: None. J. Ding: None. A. McGovern: None. M. Tutino: None. G. Villanueva Martin: None. N. Ortego-Centeno: None. J. Luis Callejas: None. J. Martin: None. G. Orozco: None.

An Integrated Workflow to Study the Promoter-Centric Spatio-Temporal Genome Architecture in Scarce Cell Populations.

Spatiotemporal gene transcription is tightly regulated by distal regulatory elements, such as enhancers and silencers, which rely on physical proximity with their target gene promoters to control transcription. Although these regulatory elements are easy to identify, their target genes are difficult to predict, since most of them are cell-type specific and may be separated by hundreds of kilobases in the linear genome sequence, skipping over other non-target genes. For several years, Promoter Capture Hi-C (PCHi-C) has been the gold standard for the association of distal regulatory elements to their target genes. However, PCHi-C relies on the availability of millions of cells, prohibiting the study of rare cell populations such as those commonly obtained from primary tissues. To overcome this limitation, low input Capture Hi-C (liCHi-C), a cost-effective and customizable method to identify the repertoire of distal regulatory elements controlling each gene of the genome, has been developed. liCHi-C relies on a similar experimental and computational framework as PCHi-C, but by employing minimal tube changes, modifyingthe reagent concentration and volumes, and swapping or eliminating steps, it accountsfor minimal material loss during library construction. Collectively, liCHi-C enables the study of gene regulation and spatiotemporal genome organization in the context of developmental biology and cellular function.

Identification of Mechanisms by Which Genetic Susceptibility Loci Influence Systemic Sclerosis Risk Using Functional Genomics in Primary T Cells and Monocytes.

Systemic sclerosis (SSc) is a complex autoimmune disease with a strong genetic component. However, most of the genes associated with the disease are still unknown because associated variants affect mostly noncoding intergenic elements of the genome. We used functional genomics to translate the genetic findings into a better understanding of the disease. Promoter capture Hi-C and RNA-sequencing experiments were performed in CD4+ T cells and CD14+ monocytes from 10 SSc patients and 5 healthy controls to link SSc-associated variants with their target genes, followed by differential expression and differential interaction analyses between cell types. We linked SSc-associated loci to 39 new potential target genes and confirmed 7 previously known SSc-associated genes. We highlight novel causal genes, such as CXCR5, as the most probable candidate gene for the DDX6 locus. Some previously known SSc-associated genes, such as IRF8, STAT4, and CD247, showed cell type-specific interactions. We also identified 15 potential drug targets already in use in other similar immune-mediated diseases that could be repurposed for SSc treatment. Furthermore, we observed that interactions were directly correlated with the expression of important genes implicated in cell type-specific pathways and found evidence that chromatin conformation is associated with genotype. Our study revealed potential causal genes for SSc-associated loci, some of them acting in a cell type-specific manner, suggesting novel biologic mechanisms that might mediate SSc pathogenesis.