Circulating tumour DNA: a minimally invasive biomarker for tumour detection and stratification

Genetic and epigenetic alterations significantly contribute to development of human cancer. Genotyping tumour tissue in search for these actionable genetic and epigenetic changes has become routine practice in oncology. However, sampling tumour tissue has significant inherent limitations. It provides only a single snapshot in time, prone to selection bias due to intra-tumour heterogeneity, and cannot always be performed owing to its invasive nature. Circulating tumour DNA (ctDNA) based liquid biopsy provides an effective alternative to invasive tissue sampling and have emerged as a minimally invasive, real-time biomarker. Recent advancements in DNA sequencing technologies have revealed enormous potential of ctDNA to improve tumour detection and stratification. In this review, we critically appraise the role of ctDNA as a liquid biopsy for cancer and evaluate the role of circulating tumour DNA as a diagnostic, prognostic and predictive biomarker. We also highlight some technical challenges and constraints associated with circulating DNA analysis

An integrative bioinformatics approach for analyses of multi-level transcriptional regulation and three-dimensional organization in the epidermis and skin appendages. Exploring genomic transcriptional profiles of the distinct stages of hair follicle and sweat gland development and analyses of mechanism integrating the transcriptional regulation, linear and high-order genome organization within epidermal differentiation complex in keratinocytes.

The transcription in the eukaryotic cells involves epigenetic regulatory mechanisms that control local and higher-order chromatin remodelling. In the skin, keratinocyte-specific genes are organized into distinct loci including Epidermal Differentiation Complex (EDC) and Keratin type I/II loci. This thesis introduces bioinformatics approaches to analyze multi-level regulatory mechanisms that control skin development and keratinocyte-specific differentiation. Firstly, integration of gene expression data with analyses of linear genome organization showed dramatic downregulation of the genes that comprise large genomic domains in the sweat glands including EDC locus, compared to ii hair follicles, suggesting substantial differences in global genome rearrangement during development of these two distinct skin appendages. Secondly, comparative analysis of the genetic programmes regulated in keratinocytes by Lhx2 transcription factor and chromatin remodeler Satb1 revealed that significant number of their target genes is clustered in the genome. Furthermore, it was shown in this study that Satb1 target genes are lineage-specific. Thirdly, analysis of the topological interactomes of Loricrin and Keratin 5 in hair follicle steam cells revealed presence of the cis- and trans-interactions and lineage specific genes (Wnt, TGF-beta/activin, Notch, etc.). Expression levels of the genes that comprise interactomes show correlation with their histone modification status. This study demonstrates the crucial role for integration of transcription factormediated and epigenetic regulatory mechanisms in establishing a proper balance of gene expression in keratinocytes during development and differentiation into distinct cell lineages and provides an integrated bioinformatics platform for further analyses of the changes in global organization of keratinocyte-specific genomic loci in normal and diseased skin

Ewastools: Infinium Human Methylation BeadChip pipeline for population epigenetics integrated into Galaxy

YesInfinium Human Methylation BeadChip is an array platform for complex evaluation of DNA methylation at an individual CpG locus in the human genome based on Illumina’s bead technology and is one of the most common techniques used in epigenome-wide association studies. Finding associations between epigenetic variation and phenotype is a significant challenge in biomedical research. The newest version, HumanMethylationEPIC, quantifies the DNA methylation level of 850,000 CpG sites, while the previous versions, HumanMethylation450 and HumanMethylation27, measured >450,000 and 27,000 loci, respectively. Although a number of bioinformatics tools have been developed to analyse this assay, they require some programming skills and experience in order to be usable. Results We have developed a pipeline for the Galaxy platform for those without experience aimed at DNA methylation analysis using the Infinium Human Methylation BeadChip. Our tool is integrated into Galaxy (http://galaxyproject.org), a web-based platform. This allows users to analyse data from the Infinium Human Methylation BeadChip in the easiest possible way. Conclusions The pipeline provides a group of integrated analytical methods wrapped into an easy-to-use interface. Our tool is available from the Galaxy ToolShed, GitHub repository, and also as a Docker image. The aim of this project is to make Infinium Human Methylation BeadChip analysis more flexible and accessible to everyone.Research Development Fund Publication Prize Award winner, May 2020

p63 transcription factor regulates nuclear shape and expression of nuclear envelope-associated genes in epidermal keratinocytes

The maintenance of a proper nuclear architecture and 3D organization of the genes, enhancer elements and transcription machinery plays an essential role in tissue development and regeneration. Here we show that in the developing skin, epidermal progenitor cells of mice lacking p63 transcription factor display alterations in the nuclear shape accompanied by marked decrease in expression of several nuclear envelop-associated components (Lamin B1, Lamin A/C, SUN1, Nesprin-3, Plectin) compared to controls. Furthermore, ChIP-qPCR assay showed enrichment of p63 on Sun1, Syne3 and Plec promoters, suggesting them as p63 targets. Alterations in the nuclei shape and expression of nuclear envelope-associated proteins were accompanied by altered distribution patterns of the repressive histone marks H3K27me3, H3K9me3 and heterochromatin protein 1- alpha in p63-null keratinocytes. These changes were also accompanied by downregulation of the transcriptional activity and relocation of the keratinocyte-specific gene loci away from the sites of active transcription towards the heterochromatin-enriched repressive nuclear compartments in p63-null cells. These data demonstrate functional links between the nuclear envelope organization, chromatin architecture and gene expression in keratinocytes and suggest nuclear envelope-associated genes as important targets mediating p63-regulated gene expression programme in the epidermis

The cellular chloride channels CLIC1 and CLIC4 contribute to virus-mediated cell motility

Ion channels regulate many aspects of cell physiology, including cell proliferation, motility, and migration, and aberrant expression and activity of ion channels is associated with various stages of tumor development, with K⁺ and Cl⁻ channels now being considered the most active during tumorigenesis. Accordingly, emerging in vitro and preclinical studies have revealed that pharmacological manipulation of ion channel activity offers protection against several cancers. Merkel cell polyomavirus (MCPyV) is a major cause of Merkel cell carcinoma (MCC), primarily because of the expression of two early regulatory proteins termed small and large tumor antigens (ST and LT, respectively). Several molecular mechanisms have been attributed to MCPyV-mediated cancer formation but, thus far, no studies have investigated any potential link to cellular ion channels. Here we demonstrate that Cl⁻ channel modulation can reduce MCPyV ST-induced cell motility and invasiveness. Proteomic analysis revealed that MCPyV ST up-regulates two Cl⁻ channels, CLIC1 and CLIC4, which when silenced, inhibit MCPyV ST-induced motility and invasiveness, implicating their function as critical to MCPyV-induced metastatic processes. Consistent with these data, we confirmed that CLIC1 and CLIC4 are up-regulated in primary MCPyV-positive MCC patient samples. We therefore, for the first time, implicate cellular ion channels as a key host cell factor contributing to virus-mediated cellular transformation. Given the intense interest in ion channel modulating drugs for human disease. This highlights CLIC1 and CLIC4 activity as potential targets for MCPyV-induced MCC

The ELIXIR Human Copy Number Variations Community:building bioinformatics infrastructure for research

Copy number variations (CNVs) are major causative contributors both in the genesis of genetic diseases and human neoplasias. While 'High-Throughput' sequencing technologies are increasingly becoming the primary choice for genomic screening analysis, their ability to efficiently detect CNVs is still heterogeneous and remains to be developed. The aim of this white paper is to provide a guiding framework for the future contributions of ELIXIR's recently established h uman CNV Community, with implications beyond human disease diagnostics and population genomics. This white paper is the direct result of a strategy meeting that took place in September 2018 in Hinxton (UK) and involved representatives of 11 ELIXIR Nodes. The meeting led to the definition of priority objectives and tasks, to address a wide range of CNV-related challenges ranging from detection and interpretation to sharing and training. Here, we provide suggestions on how to align these tasks within the ELIXIR Platforms strategy, and on how to frame the activities of this new ELIXIR Community in the international context

Cbx4 maintains the epithelial lineage identity and cell proliferation in the developing stratified epithelium

During development, multipotent progenitor cells establish lineage-specific programmers of gene activation and silencing underlying their differentiation into specialized cell types. We show that the Polycomb component Cbx4 serves as a critical determinant that maintains the epithelial identity in the developing epidermis by repressing nonepidermal gene expression programs. Cbx4 ablation in mice results in a marked decrease of the epidermal thickness and keratinocyte (KC) proliferation associated with activation of numerous neuronal genes and genes encoding cyclin-dependent kinase inhibitors (p16/p19 and p57). Furthermore, the chromodomain- and SUMO E3 ligase–dependent Cbx4 activities differentially regulate proliferation, differentiation, and expression of nonepidermal genes in KCs. Finally, Cbx4 expression in KCs is directly regulated by p63 transcription factor, whereas Cbx4 overexpression is capable of partially rescuing the effects of p63 ablation on epidermal development. These data demonstrate that Cbx4 plays a crucial role in the p63-regulated program of epidermal differentiation, maintaining the epithelial identity and proliferative activity in KCs via repression of the selected nonepidermal lineage and cell cycle inhibitor genes

p63 regulates Satb1 to control tissue-specific chromatin remodeling during development of the epidermis

Genome organizer Satb1 is regulated by p63 and contributes to epidermal morphogenesis by remodeling chromatin structure and gene expression at the epidermal differentiation complex locus

MCV-miR-M1 targets the host-cell immune response resulting in the attenuation of neutrophil chemotaxis

Virus-encoded miRNAs are emerging as key regulators of persistent infection and host-cell immune evasion. Merkel cell polyomavirus (MCPyV), the predominant aetiological agent of Merkel cell carcinoma (MCC), encodes a single miRNA, MCV-miR-M1, which targets the oncogenic MCPyV large T antigen (LT). MCV-miR-M1 has previously been shown to play an important role in establishment of long-term infection, however, the underlying mechanism is not fully understood. A key unanswered question is whether, in addition to auto-regulating LT, MCV-miR-M1 also targets cellular transcripts to orchestrate an environment conducive for persistent infection. To address this, we adopted an RNA-Seq-based approach to identify cellular targets of MCV-miR-M1. Intriguingly, bioinformatics analysis of transcripts that are differentially expressed in cells expressing MCV-miR-M1 revealed several genes implicated in immune evasion. Subsequent target validation led to the identification of the innate immunity protein, SP100, as a direct target of MCV-miR-M1. Moreover, MCV-miR-M1-mediated modulation of SP100 was associated with a significant decrease in CXCL8 secretion, resulting in the attenuation of neutrophil chemotaxis towards Merkel cells harbouring synthetic MCPyV. Based on these observations we propose that MCV-miR-M1 targets key immune response regulators to help facilitate persistent infection, which is a pre-requisite for cellular transformation in MCC

5C analysis of the Epidermal Differentiation Complex locus reveals distinct chromatin interaction networks between gene-rich and gene-poor TADs in skin epithelial cells

YesMammalian genomes contain several dozens of large (>0.5 Mbp) lineage-specific gene loci harbouring functionally related genes. However, spatial chromatin folding, organization of the enhancer-promoter networks and their relevance to Topologically Associating Domains (TADs) in these loci remain poorly understood. TADs are principle units of the genome folding and represents the DNA regions within which DNA interacts more frequently and less frequently across the TAD boundary. Here, we used Chromatin Conformation Capture Carbon Copy (5C) technology to characterize spatial chromatin interaction network in the 3.1 Mb Epidermal Differentiation Complex (EDC) locus harbouring 61 functionally related genes that show lineage-specific activation during terminal keratinocyte differentiation in the epidermis. 5C data validated by 3D-FISH demonstrate that the EDC locus is organized into several TADs showing distinct lineage-specific chromatin interaction networks based on their transcription activity and the gene-rich or gene-poor status. Correlation of the 5C results with genome-wide studies for enhancer-specific histone modifications (H3K4me1 and H3K27ac) revealed that the majority of spatial chromatin interactions that involves the gene-rich TADs at the EDC locus in keratinocytes include both intra- and inter-TAD interaction networks, connecting gene promoters and enhancers. Compared to thymocytes in which the EDC locus is mostly transcriptionally inactive, these interactions were found to be keratinocyte-specific. In keratinocytes, the promoter-enhancer anchoring regions in the gene-rich transcriptionally active TADs are enriched for the binding of chromatin architectural proteins CTCF, Rad21 and chromatin remodeler Brg1. In contrast to gene-rich TADs, gene-poor TADs show preferential spatial contacts with each other, do not contain active enhancers and show decreased binding of CTCF, Rad21 and Brg1 in keratinocytes. Thus, spatial interactions between gene promoters and enhancers at the multi-TAD EDC locus in skin epithelial cells are cell type-specific and involve extensive contacts within TADs as well as between different gene-rich TADs, forming the framework for lineage-specific transcription.This study was supported by the grants 5R01AR064580 and 1RO1AR071727 to VAB, TKS and AAS, as well as by the grants from MRC (MR/ M010015/1) and BBSRC (BB/K010050/1) to VAB