Project description:These tracks include chromatin interaction data produced using the 5C (chromatin conformation capture carbon copy) method by the Kenter Lab located at the University of Illinois College of Medicine, Chicago, IL. These tracks show looping interactions across the Igh locus using alternating forward and reverse primer design scheme. The 3C method uses formaldehyde crosslinking to covalently associate interacting chromatin segments in intact cells. The cells are then lysed and chromatin is digested with the Hind III restriction enzyme. The digested fragments are ligated under dilute conditions to promote intra-molecular ligation. A genome-wide interaction library of ligation products corresponding to all possible chromatin interactions is produced by this method. In 5C assays, over 12,000 potential ligation products specific to the Igh locus are detected by PCR using multiplexed primer pairs. Here we focused on the 3’ end of the Igh locus to evaluate the status of the constant region domain of the locus in LPS+IL4 activated splenic B cells. We observe that the configuration of the 3’ end of the Igh locus spanning the CH region genes assumes a developmental stage specific configuration in B lineage B cells. We find that the interaction frequency and activation state of the 3’ enhancer increases as B cells mature.
Project description:These tracks include chromatin interaction data produced using the 5C (chromatin conformation capture carbon copy) method by the Kenter Lab located at the University of Illinois College of Medicine, Chicago, IL. These tracks show looping interactions across the Igh locus using alternating forward and reverse primer design scheme. The 3C method uses formaldehyde crosslinking to covalently associate interacting chromatin segments in intact cells. The cells are then lysed and chromatin is digested with the Hind III restriction enzyme. The digested fragments are ligated under dilute conditions to promote intra-molecular ligation. A genome-wide interaction library of ligation products corresponding to all possible chromatin interactions is produced by this method. In 5C assays, over 12,000 potential ligation products specific to the Igh locus are detected by PCR using multiplexed primer pairs. Here we focused on the 3’ end of the Igh locus to evaluate the status of the constant region domain of the locus in LPS+IL4 activated splenic B cells. We observe that the configuration of the 3’ end of the Igh locus spanning the CH region genes assumes a developmental stage specific configuration in B lineage B cells. We find that the interaction frequency and activation state of the 3’ enhancer increases as B cells mature.
Project description:These tracks include chromatin interaction data produced using the 5C (chromatin conformation capture carbon copy) method by the Kenter Lab located at the University of Illinois College of Medicine, Chicago, IL. These tracks show looping interactions across the Igh locus using alternating forward and reverse primer design scheme. The 3C method uses formaldehyde crosslinking to covalently associate interacting chromatin segments in intact cells. The cells are then lysed and chromatin is digested with the Hind III restriction enzyme. The digested fragments are ligated under dilute conditions to promote intra-molecular ligation. A genome-wide interaction library of ligation products corresponding to all possible chromatin interactions is produced by this method. In 5C assays, over 12,000 potential ligation products specific to the Igh locus are detected by PCR using multiplexed primer pairs. These studies have revealed three conserved topological sub-domains. Each topological folds encompasses a major VH gene family. The Pax5 transcription factor organizes the topological sub-domain that spans the VHJ558 gene family. In the absence of Pax5, the distal J558 VH genes fail to associate with the proximal VH genes, thus providing an explanation for reduced VHJ558 gene rearrangements in Pax5-deficient pro-B cells. We propose that Igh locus contraction is the cumulative effect of several independently controlled chromatin sub-domains that provide the structural infrastructure to coordinate optimal antigen receptor assembly (Montefiori et al. 2015). We also note that the configuration of the 3’ end of the Igh locus spanning the CH region genes assumes a developmental stage specific configuration in pro-B cells that appreas to skew class switch recombination to specific isotypes. This 3D spatial configuration is lost in resting splenic B cells that are capable of class switch recombination to all isotypes (Kumar et al. 2013).
Project description:The immunoglobulin heavy-chain (Igh) locus undergoes large-scale contraction in pro-B cells, which facilitates VH-DJH recombination by juxtaposing distal VH genes next to the DJH- rearranged gene segment in the proximal Igh domain. By high-resolution mapping of long-range interactions, we now demonstrate that an array of local interaction domains establishes the three- dimensional structure of the extended Igh locus in lymphoid progenitors and thymocytes. In pro- B cells, these local domains engage in long-range interactions across the entire Igh locus, which depend on the transcription factors Pax5, YY1 and CTCF. The large VH gene cluster thereby undergoes flexible long-range interactions with the more rigidly structured 3M-bM-^@M-^Y proximal domain, which ensures that all VH genes can participate with similar probability in VH-DJH recombination to generate a diverse antibody repertoire. Notably, these long-range interactions appear to be an intrinsic feature of the VH gene cluster, as they are still generated upon mutation of the EM-NM-< enhancer, IGCR1 insulator or 3M-bM-^@M-^Y regulatory region present in the 3M-bM-^@M-^Y proximal Igh domain. 4C sequencing from mutliple celltypes with multiple viewpoints; uneven number of replicates ChIP-Seq
Project description:The immunoglobulin heavy-chain (Igh) locus undergoes large-scale contraction in pro-B cells, which facilitates VH-DJH recombination by juxtaposing distal VH genes next to the DJH- rearranged gene segment in the proximal Igh domain. By high-resolution mapping of long-range interactions, we now demonstrate that an array of local interaction domains establishes the three- dimensional structure of the extended Igh locus in lymphoid progenitors and thymocytes. In pro- B cells, these local domains engage in long-range interactions across the entire Igh locus, which depend on the transcription factors Pax5, YY1 and CTCF. The large VH gene cluster thereby undergoes flexible long-range interactions with the more rigidly structured 3’ proximal domain, which ensures that all VH genes can participate with similar probability in VH-DJH recombination to generate a diverse antibody repertoire. Notably, these long-range interactions appear to be an intrinsic feature of the VH gene cluster, as they are still generated upon mutation of the Eμ enhancer, IGCR1 insulator or 3’ regulatory region present in the 3’ proximal Igh domain.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Non-coding sense and antisense germline transcription within the immunoglobulin heavy chain locus precedes V(D)J recombination and has been proposed to be associated with Igh locus accessibility, although its precise role remains elusive. However, no global analysis of germline transcription throughout the Igh locus has been done. Therefore, we performed directional RNAseq, demonstrating the locations and extent of both sense and antisense transcription throughout the Igh locus. Surprisingly, the majority of antisense transcripts are localized around two PAIR elements in the distal IghV region. Importantly, long-distance loops measured by 3C are observed between these two active PAIR promoters and EM-NM-<, the start site of IM-NM-< germline transcription, in a lineage- and stage-specific manner, even though this antisense transcription is EM-NM-<-independent. YY1-/- pro-B cells are greatly impaired in distal VH gene rearrangement and Igh locus compaction, and we demonstrate that YY1 deficiency greatly reduces antisense transcription and PAIR-EM-NM-< interactions. ChIP-seq shows high level YY1 binding only at EM-NM-<, but low levels near some antisense promoters. PAIR-EM-NM-< interactions are not disrupted by DRB, which blocks transcription elongation without disrupting transcription factories once they are established, but the looping is reduced after heat shock treatment, which disrupts transcription factories. We propose that transcription-mediated interactions, most likely at transcription factories, initially compact the Igh locus, bringing distal VH genes close to the DJH rearrangement, which is adjacent to EM-NM-<. Therefore, we hypothesize that one key role of non-coding germline transcription is to facilitate locus compaction, allowing distal VH genes to undergo efficient rearrangement. ChIP Seq YY1 vs. input control
Project description:To produce a diverse antibody repertoire, immunoglobulin heavy-chain (Igh) loci undergo large-scale alterations in structure to facilitate juxtaposition and recombination of spatially separated variable (VH), diversity (DH), and joining (JH) genes. These chromosomal alterations are poorly understood. Uncovering their patterns shows how chromosome dynamics underpins antibody diversity. Using tiled Capture Hi-C, we produce a comprehensive map of chromatin interactions throughout the 2.8-Mb Igh locus in progenitor B cells. We find that the Igh locus folds into semi-rigid subdomains and undergoes flexible looping of the VH genes to its 3′ end, reconciling two views of locus organization. Deconvolution of single Igh locus conformations using polymer simulations identifies thousands of different structures. This heterogeneity may underpin the diversity of V(D)J recombination events. All three immunoglobulin loci also participate in a highly specific, developmentally regulated network of interchromosomal interactions with genes encoding B cell-lineage factors. This suggests a model of interchromosomal coordination of B cell development.