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Project description:Genome-wide association studies found that increased risk for atrial fibrillation (AF), the most common human heart arrhythmia, is associated with noncoding sequence variants located in proximity to PITX2 Cardiomyocyte-specific epigenomic and comparative genomics uncovered 2 AF-associated enhancers neighboring PITX2 with varying conservation in mice. Chromosome conformation capture experiments in mice revealed that the Pitx2c promoter directly contacted the AF-associated enhancer regions. CRISPR/Cas9-mediated deletion of a 20-kb topologically engaged enhancer led to reduced Pitx2c transcription and AF predisposition. Allele-specific chromatin immunoprecipitation sequencing on hybrid heterozygous enhancer knockout mice revealed that long-range interaction of an AF-associated region with the Pitx2c promoter was required for maintenance of the Pitx2c promoter chromatin state. Long-range looping was mediated by CCCTC-binding factor (CTCF), since genetic disruption of the intronic CTCF-binding site caused reduced Pitx2c expression, AF predisposition, and diminished active chromatin marks on Pitx2 AF risk variants located at 4q25 reside in genomic regions possessing long-range transcriptional regulatory functions directed at PITX2.
| S-EPMC6842642 | biostudies-literature
Project description:Genome-wide association studies (GWAS) have found that increased risk for atrial fibrillation (AF), the most common type of arrhythmia in humans, is associated with non-coding sequence variants located in proximity to the PITX2 homeobox gene. Using cardiomyocyte-specific epigenomic and comparative genomic analyses, we identified two AF-associated enhancers neighboring PITX2 with varying degrees of conservation in mice. Pitx2c promoter directly contacted the AF-associated enhancer regions. CRISPR/Cas9 mediated deletion of a 20 kb long topologically engaged enhancer lead to reduced Pitx2c transcription and AF predisposition. Allele-specific ChIP-seq and CUT&RUN experiments showed that long-range interaction of this AF-associated region with the Pitx2c promoter was required for maintenance of the Pitx2c promoter chromatin state. Moreover, long-range looping was mediated by CTCF, as the genetic disruption of an intronic CTCF binding site caused decreased Pitx2c cardiac expression, AF predisposition, and reduced active chromatin marks on Pitx2. Our findings reveal that AF risk variants located at 4q25 reside in genomic regions possessing long-range transcriptional regulatory functions directed at PITX2
2019-10-08 | GSE138529 | GEO
Project description:Genome-wide association studies (GWAS) have found that increased risk for atrial fibrillation (AF), the most common type of arrhythmia in humans, is associated with non-coding sequence variants located in proximity to the PITX2 homeobox gene. Using cardiomyocyte-specific epigenomic and comparative genomic analyses, we identified two AF-associated enhancers neighboring PITX2 with varying degrees of conservation in mice. Pitx2c promoter directly contacted the AF-associated enhancer regions. CRISPR/Cas9 mediated deletion of a 20 kb long topologically engaged enhancer lead to reduced Pitx2c transcription and AF predisposition. Allele-specific ChIP-seq and CUT&RUN experiments showed that long-range interaction of this AF-associated region with the Pitx2c promoter was required for maintenance of the Pitx2c promoter chromatin state. Moreover, long-range looping was mediated by CTCF, as the genetic disruption of an intronic CTCF binding site caused decreased Pitx2c cardiac expression, AF predisposition, and reduced active chromatin marks on Pitx2. Our findings reveal that AF risk variants located at 4q25 reside in genomic regions possessing long-range transcriptional regulatory functions directed at PITX2
2019-10-08 | GSE138528 | GEO
Project description:Long-range Pitx2c Enhancer Promoter Interactions Prevent Predisposition to Atrial Fibrillation
| PRJNA576253 | ENA
Project description:Long-range Pitx2c Enhancer Promoter Interactions Prevent Predisposition to Atrial Fibrillation
| PRJNA671280 | ENA
Project description:Long-range Pitx2c Enhancer Promoter Interactions Prevent Predisposition to Atrial Fibrillation [ChIP-seq]
| PRJNA576256 | ENA
Project description:Long-range Pitx2c Enhancer Promoter Interactions Prevent Predisposition to Atrial Fibrillation [RNA-seq]
| PRJNA576255 | ENA
Project description:BackgroundRecent genome-wide association studies have uncovered genomic loci that underlie an increased risk for atrial fibrillation, the major cardiac arrhythmia in humans. The most significant locus is located in a gene desert at 4q25, approximately 170 kilobases upstream of PITX2, which codes for a transcription factor involved in embryonic left-right asymmetry and cardiac development. However, how this genomic region functionally and structurally relates to PITX2 and atrial fibrillation is unknown.ResultsTo characterise its function, we tested genomic fragments from 4q25 for transcriptional activity in a mouse atrial cardiomyocyte cell line and in transgenic mouse embryos, identifying a non-tissue-specific potentiator regulatory element. Chromosome conformation capture revealed that this region physically interacts with the promoter of the cardiac specific isoform of Pitx2. Surprisingly, this regulatory region also interacts with the promoter of the next neighbouring gene, Enpep, which we show to be expressed in regions of the developing mouse heart essential for cardiac electrical activity.ConclusionsOur data suggest that de-regulation of both PITX2 and ENPEP could contribute to an increased risk of atrial fibrillation in carriers of disease-associated variants, and show the challenges that we face in the functional analysis of genome-wide disease associations.
| S-EPMC4416339 | biostudies-literature
Project description:We examined how remote enhancers establish physical communication with target promoters to activate gene transcription in response to environmental signals. Although the natural IFN-beta enhancer is located immediately upstream of the core promoter, it also can function as a classical enhancer element conferring virus infection-dependent activation of heterologous promoters, even when it is placed several kilobases away from these promoters. We demonstrated that the remote IFN-beta enhancer "loops out" the intervening DNA to reach the target promoter. These chromatin loops depend on sequence-specific transcription factors bound to the enhancer and the promoter and thus can explain the specificity observed in enhancer-promoter interactions, especially in complex genetic loci. Transcription factor binding sites scattered between an enhancer and a promoter can work as decoys trapping the enhancer in nonproductive loops, thus resembling insulator elements. Finally, replacement of the transcription factor binding sites involved in DNA looping with those of a heterologous prokaryotic protein, the lambda repressor, which is capable of loop formation, rescues enhancer function from a distance by re-establishing enhancer-promoter loop formation.
| S-EPMC2779200 | biostudies-literature
Project description:ObjectiveThis study aimed to identify novel PITX2c mutations responsible for idiopathic atrial fibrillation.MethodsA cohort of 210 unrelated patients with idiopathic atrial fibrillation and 200 unrelated, ethnically matched healthy individuals used as controls were recruited. The whole coding exons and splice junctions of the PITX2c gene, which encodes a paired-like homeobox transcription factor required for normal cardiovascular morphogenesis, were sequenced in 210 patients and 200 control subjects. The causative potentials of the identified mutations were automatically predicted by MutationTaster and PolyPhen-2. The functional characteristics of the PITX2c mutations were explored using a dual-luciferase reporter assay system.ResultsTwo novel heterozygous PITX2c mutations (p.Q105L and p.R122C) were identified in 2 of the 210 unrelated patients with idiopathic atrial fibrillation. These missense mutations were absent in the 400 control chromosomes and were both predicted to be pathogenic. Multiple alignments of PITX2c protein sequences across various species showed that the altered amino acids were highly evolutionarily conserved. A functional analysis demonstrated that the mutant PITX2c proteins were both associated with significantly reduced transcriptional activity compared with their wild-type counterparts.ConclusionThe findings of this study associate PITX2c loss-of-function mutations with atrial fibrillation, supporting the hypothesis that dysfunctional PITX2c confers enhanced susceptibility to atrial fibrillation and suggesting potential implications for early prophylaxis and allele-specific therapy for this common arrhythmia.
| S-EPMC3870307 | biostudies-literature