Project description:Emerging 3D genome mapping efforts suggest complex chromosomal folding structures. However, the true multiplex nature of chromatin interactions has yet to be fully explored. Here, we describe a chromatin interaction analysis by droplet-based sequencing (ChIA-Drop). In ChIA-Drop, individual chromatin complexes are partitioned into droplets that contain a gel bead of DNA-barcoded primers, such that tethered chromatin DNA fragments are uniquely indexed and amplified for sequencing and mapping to demarcate multiplex chromatin contacts. Thus, ChIA-Drop can identify complex chromatin interactions with unprecedented single-molecule precision, which is not possible using methods that analyze pairwise contacts via proximity ligation. We demonstrate that multiplex chromatin interactions predominantly contribute to topologically associated domains with high heterogeneity, and that multivalent promoter-centered interactions provide a topological model for gene transcription.
Project description:The dynamically organized chromatin complexes often involve multiplex chromatin interactions and sometimes chromatin-associated RNA (caRNA). Chromatin complex compositions change during cellular differentiation and aging, and are expected to be highly heterogeneous among terminally differentiated single cells. Here we introduce the Multi-Nucleic Acid Interaction Mapping in Single Cell (MUSIC) technique for concurrent profiling of multiplex chromatin interactions, gene expression, and RNA-chromatin associations within individual nuclei. Applied to 14 human frontal cortex samples from elderly donors, MUSIC delineates diverse cortical cell types and states. We observed the nuclei exhibiting fewer short-range chromatin interactions are correlated with an “older” transcriptomic signature and with Alzheimer’s pathology. Furthermore, the cell type exhibiting chromatin contacts between cis expression quantitative trait loci (cis eQTLs) and a promoter tends to be the cell type where these cis eQTLs specifically affect their target gene’s expression. Additionally, the female cortical cells exhibit highly heterogeneous interactions between the XIST non-coding RNA and Chromosome X, along with diverse spatial organizations of the X chromosomes. MUSIC presents a potent tool for exploring chromatin architecture and transcription at cellular resolution in complex tissues.
Project description:We apply ChIA-Drop, a single-molecule ligation-free mapping technique, to visualize loop formation over time. Our results demonstrated a cohesin-centric framework that coordinates with CTCF and RNAPII, respectively. At the loading (NIPBL binding) site, cohesin is highly correlated with transcriptional activities and translocates bi-directionally toward CTCF motif sites, where CTCF likely provides the anchoring point for cohesin to actively reel the chromatin template according to the motif forward orientation. Furthermore, cohesin specifically co-localizes with RNAPII and together mediates multiplex chromatin interactions that involve promoters, enhancers and super-enhancers. Intriguingly, single-molecule mapping data revealed that individual constituents of super-enhancers interact with target genes singularly and in cascade through intermediate regulatory elements, suggesting a probability-based mechanism for transcription regulation.
Project description:SAMOSA is a single-molecule oligonucleosome footprinting technology, which can be employed to reveal nucleosome patterns (nucleosome positioning, nucleosome repeat length) at transcription factor binding sites and epigenomic domains.
Project description:High-precision mapping of nuclear pore-chromatin interactions reveals new principles of genome organization at the nuclear envelope
Project description:We develop a small molecule-inducible dimerization strategy of RBP of interest and adenosine deaminase domain to profile dynamic RBP-RNA interactions.