Biology subjects

Bihary, D.

Publications and source records attributed to Bihary, D..

4 recordsLinked to original sources

bioRxiv2020

Identifying regulatory and spatial genomic architectural elements using cell type independent machine and deep learning models

Chromosome conformation capture methods such as Hi-C enables mapping of genome-wide chromatin interactions and is a promising technology to understand the role of spatial chromatin organisation in gene regulation. However, the generation and analysis of these data sets at high resolutions remain technically challenging and costly. We developed a machine and deep learning approach to predict functionally important, highly interacting chromatin regions (HICR) and topologically associated domain (TAD) boundaries independent of Hi-C data in both normal physiological states and pathological conditions such as cancer. This approach utilises gradient boosted trees and convolutional neural networks trained on both Hi-C and histone modification epigenomic data from three different cell types. Given only epigenomic modification data these models are able to predict chromatin interactions and TAD boundaries with high accuracy. We demonstrate that our models are transferable across cell types, indicating that combinatorial histone mark signatures may be universal predictors for highly interacting chromatin regions and spatial chromatin architecture elements.

genomics↗

bioRxiv2020

SpiderSeqR: an R package for crawling the web of high-throughput multi-omic data repositories for data-sets and annotation

AO_SCPLOWBSTRACTC_SCPLOWMore than three decades ago, the microarray revolution brought about high-throughput data generation capability to biology and medicine. Subsequently, the emergence of massively parallel sequencing technologies led to many big-data initiatives such as the human genome project and the encyclopedia of DNA elements (ENCODE) project. These, in combination with cheaper, faster massively parallel DNA sequencing capabilities, have democratised multi-omic (genomic, transcriptomic, translatomic and epigenomic) data generation leading to a data deluge in bio-medicine. While some of these data-sets are trapped in inaccessible silos, the vast majority of these data-sets are stored in public data resources and controlled access data repositories, enabling their wider use (or misuse). Currently, most peer reviewed publications require the deposition of the data-set associated with a study under consideration in one of these public data repositories. However, clunky and difficult to use interfaces, subpar or incomplete annotation prevent discovering, searching and filtering of these multi-omic data and hinder their re-purposing in other use cases. In addition, the proliferation of multitude of different data repositories, with partially redundant storage of similar data are yet another obstacle to their continued usefulness. Similarly, interfaces where annotation is spread across multiple web pages, use of accession identifiers with ambiguous and multiple interpretations and lack of good curation make these data-sets difficult to use. We have produced SpiderSeqR, an R package, whose main features include the integration between NCBI GEO and SRA databases, enabling an integrated unified search of SRA and GEO data-sets and associated annotations, conversion between database accessions, as well as convenient filtering of results and saving past queries for future use. All of the above features aim to promote data reuse to facilitate making new discoveries and maximising the potential of existing data-sets. Availabilityhttps://github.com/ss-lab-cancerunit/SpiderSeqR

bioinformatics↗

bioRxiv2019

Transcription-driven cohesin repositioning rewires chromatin loops in cellular senescence

Senescence is a phenotypic state of stable proliferative arrest, typically occurring in lineage-committed cells and triggered by various stimuli. It is generally accompanied by activation of a secretory program (senescence-associated secretory phenotype, SASP), which modulates both local (tissue microenvironment) and systemic (ageing) homeostasis1,2. Enhancer-promoter interactions play a key role in gene regulation3-5, facilitated by chromatin loops, mostly formed via CCCTC binding factor (CTCF) and cohesin tethering6-8. The three-dimensional chromatin structure of senescent cells has been characterised9-11 mostly in terms of macro-domain structures, but its relevance in gene expression remains elusive. Here, we use Hi-C and capture Hi-C12,13 to show that oncogenic HRAS-induced senescence (RIS) in human diploid fibroblasts (HDFs) is accompanied by extensive enhancer-promoter rewiring, which is closely connected with dynamic cohesin binding to the genome. We find de novo cohesin peaks at the 3 end of a subset of active genes, reminiscent of the transcription-driven cohesin islands recently discovered in mouse embryonic fibroblasts deficient in both CTCF and the cohesin release factor Wings apart-like (Wapl)14. RIS de novo cohesin peaks are also transcription-dependent and enriched for SASP genes, as exemplified by IL1B, where de novo cohesin binding is involved in new loop formation. Cytokine induction is associated with similar cohesin islands appearance and enhancer-promoter rewiring during the terminal differentiation of monocytes to macrophages15, but not upon acute TNF treatment of HDFs16. These results suggest that RIS represents a fate-determined process in which gene expression is regulated beyond the cell type specific 3D chromatin framework, in part through cohesin redistribution.

molecular biology↗

bioRxiv2017

NOTCH-mediated non-cell autonomous regulation of chromatinstructure during senescence

Senescent cells interact with the surrounding microenvironment achieving diverse functional outcomes. In addition to autocrine and paracrine signalling mediated by factors of the senescence-associated secretory phenotype, we have recently identified that NOTCH1 can drive lateral induction of a unique form of senescence in adjacent cells through specific induction of the NOTCH ligand JAG1. Here we show that NOTCH signalling can modulate chromatin structure both autonomously and non-autonomously. In addition to senescence-associated heterochromatic foci (SAHF), oncogenic RAS-induced senescent (RIS) cells in culture exhibit a massive increase in nucleosome-free regions (NRFs). NOTCH signalling suppresses both SAHF and NFR formation in this context. Strikingly, NOTCH-induced senescent cells, or cancer cells with high JAG1 expression, also drive similar chromatin architectural changes in adjacent cells through cell-cell contact. Mechanistically, we show that NOTCH signalling represses the chromatin architectural protein HMGA1, an association found in a range of human cancers. Thus, HMGA1 is involved not only in SAHFs, but also RIS-specific NFR formation. In conclusion, this study identifies that the JAG1-NOTCH-HMGA1 axis mediates the juxtacrine regulation of chromatin architecture.

cell biology↗