Perry, J. K. | Search bioRxiv

bioRxiv2018

Migration through a small pore disrupts inactive chromatin organisation in neutrophil-like cells

BackgroundMammalian cells are flexible and can rapidly change shape when they contract, adhere, or migrate. Their nucleus must be stiff enough to withstand cytoskeletal forces, but flexible enough to remodel as the cell changes shape. This is particularly important for cells migrating through constricted space, where the nuclear shape must change in order to fit through the constriction. This occurs many times in the life cycle of a neutrophil, which must protect its chromatin from damage and disruption associated with migration.\n\nResultsTotal RNA-sequencing identified that neutrophil migration through 5 or 14m pores was associated with changes in the transcript levels of inflammation and chemotaxis-related genes, when compared to unmigrated cells. Differentially expressed transcripts specific to migration with constriction were enriched for groups of genes associated with cytoskeletal remodeling.\n\nHi-C was used to capture the genome organization in control and migrated cells. Minimal switching was observed between the active (A) and inactive (B) compartments after migration. However, global depletion of short range contacts was observed following migration with constriction compared to migration without constriction. Regions with disrupted contacts, TADs, and compartments were enriched for inactive chromatin.\n\nConclusionShort range genome organization is preferentially altered in inactive chromatin, possibly protecting transcriptionally active contacts from the disruptive effects of migration with constriction. This is consistent with current hypotheses implicating heterochromatin as the mechanoresponsive form of chromatin. Further investigation concerning the contribution of heterochromatin to stiffness, flexibility, and protection of nuclear function will be important for understanding cell migration in human health and disease.

genomics↗

bioRxiv2018

Type 1 diabetes mellitus-associated genetic variants contribute to overlapping immune regulatory networks

Type 1 diabetes (T1D) is a chronic metabolic disorder characterised by the autoimmune destruction of insulin-producing pancreatic islet beta cells in genetically predisposed individuals. Genome-wide association studies (GWAS) have identified over 60 risk loci across the human genome, marked by single nucleotide polymorphisms (SNPs), which confer genetic predisposition to T1D. There is increasing evidence that disease-associated SNPs can alter gene expression through spatial interactions that involve distal loci, in a tissue-and development-specific manner. Here, we used three-dimensional (3D) genome organization data to identify genes that physically co-localized with DNA regions that contained T1D-associated SNPs in the nucleus. Analysis of these SNP-gene pairs using the Genotype-Tissue Expression database identified a subset of SNPs that significantly affected gene expression. We identified 298 spatially regulated genes including HLA-DRB1, LAT, MICA, BTN3A2, CTLA4, CD226, NOTCH1, TRIM26, CLEC2B, TYK2, and FLRT3, which exhibit tissue-specific effects in multiple tissues. We observed that the T1D-associated variants interconnect through networks that form part of the immune regulatory pathways, including immune-cell activation, cytokine signalling, and programmed cell death protein-1 (PD-1). These pathways have been implicated in the pancreatic beta-cell inflammation and destruction as observed in T1D. Our results demonstrate that T1D-associated variants contribute to adaptive immune signalling, and immune-cell proliferation and activation through tissue and cell-type specific regulatory networks.\n\nAuthor SummaryAlthough genome-wide association studies have identified risk regions across the human genome that predispose individuals to the development of type 1 diabetes (T1D), the mechanisms through which these regions contribute to disease is unclear. Here, we used population-based genetic data from genome-wide association studies (GWAS) to understand how the three-dimensional (3D) organization of the DNA contributes to the differential expression of genes involved in immune system dysregulation as observed in T1D. We identified interconnected regulatory networks that affect immune pathways (adaptive immune signalling and immune-cell proliferation and activation) in a tissue and cell-type specific manner. Some of these pathways are implicated in the pancreatic beta-cell destruction. However, we observed other regulatory changes in tissues that are not typically considered to be central to the pathology of T1D, which represents a novel insight into the disease. Collectively, our data represent a novel resource for the hypothesis-driven development of diagnostic, prognostic and therapeutic interventions in T1D.

genetics↗