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Journal articleWang H, Bender A, Wang P, et al., 2017,
Insights into beta cell regeneration for diabetes via integration of molecular landscapes in human insulinomas, Nature Communications, Vol: 8, Pages: 1-15, ISSN: 2041-1723
Although diabetes results in part from a deficiency of normal pancreatic beta cells, inducing human beta cells to regenerate is difficult. Reasoning that insulinomas hold the “genomic recipe” for beta cell expansion, we surveyed 38 human insulinomas to obtain insights into therapeutic pathways for beta cell regeneration. An integrative analysis of whole-exome and RNA-sequencing data was employed to extensively characterize the genomic and molecular landscape of insulinomas relative to normal beta cells. Here, we show at the pathway level that the majority of the insulinomas display mutations, copy number variants and/or dysregulation of epigenetic modifying genes, most prominently in the polycomb and trithorax families. Importantly, these processes are coupled to co-expression network modules associated with cell proliferation, revealing candidates for inducing beta cell regeneration. Validation of key computational predictions supports the concept that understanding the molecular complexity of insulinoma may be a valuable approach to diabetes drug discovery.
Journal articlevan Arensbergen J, Dussaud S, Pardanaud-Glavieux C, et al., 2017,
A distal intergenic region controls pancreatic endocrine differentiation by acting as a transcriptional enhancer and as a polycomb response element, PLOS ONE, Vol: 12, ISSN: 1932-6203
Lineage-selective expression of developmental genes is dependent on the interplay between activating and repressive mechanisms. Gene activation is dependent on cell-specific transcription factors that recognize transcriptional enhancer sequences. Gene repression often depends on the recruitment of Polycomb group (PcG) proteins, although the sequences that underlie the recruitment of PcG proteins, also known as Polycomb response elements (PREs), remain poorly understood in vertebrates. While distal PREs have been identified in mammals, a role for positive-acting enhancers in PcG-mediated repression has not been described. Here we have used a highly efficient procedure based on lentiviral-mediated transgenesis to carry out in vivo fine-mapping of, cis-regulatory sequences that control lineage-specific activation of Neurog3, a master regulator of pancreatic endocrine differentiation. Our findings reveal an enhancer region that is sufficient to drive correct spacio-temporal expression of Neurog3 and demonstrate that this same region serves as a PRE in alternative lineages where Neurog3 is inactive.
Journal articleAkerman I, Tu Z, Beucher A, et al., 2017,
Recent studies have uncovered thousands of long non-coding RNAs (lncRNAs) in human pancreatic β cells. β cell lncRNAs are often cell type specific and exhibit dynamic regulation during differentiation or upon changing glucose concentrations. Although these features hint at a role of lncRNAs in β cell gene regulation and diabetes, the function of β cell lncRNAs remains largely unknown. In this study, we investigated the function of β cell-specific lncRNAs and transcription factors using transcript knockdowns and co-expression network analysis. This revealed lncRNAs that function in concert with transcription factors to regulate β cell-specific transcriptional networks. We further demonstrate that the lncRNA PLUTO affects local 3D chromatin structure and transcription of PDX1, encoding a key β cell transcription factor, and that both PLUTO and PDX1 are downregulated in islets from donors with type 2 diabetes or impaired glucose tolerance. These results implicate lncRNAs in the regulation of β cell-specific transcription factor networks.
Journal articleJohnston NR, Mitchell RK, Haythorne E, et al., 2016,
The arrangement of beta cells within islets of Langerhans is critical for insulin release through thegeneration of rhythmic activity. A privileged role for individual beta cells in orchestrating theseresponses has long-been suspected, but not directly demonstrated. We show here that the beta cellpopulation in situ is operationally heterogeneous. Mapping of islet functional architecturerevealed the presence of hub cells with pacemaker properties, which remain stable over recordingperiods of 2-3 hours. Using a dual optogenetic/photopharmacological strategy, silencing of hubsabolished coordinated islet responses to glucose, whereas specific stimulation restoredcommunication patterns. Hubs were metabolically-adapted and targeted by both proinflammatoryand glucolipotoxic insults to induce widespread beta cell dysfunction. Thus, theislet is wired by hubs, whose failure may contribute to type 2 diabetes mellitus.
Journal articleFerrer J, Real FX, 2016,
Journal articleArnes L, Akerman I, Balderes DA, et al., 2016,
Pancreatic β cells are responsible for maintaining glucose homeostasis; their absence or malfunction results in diabetes mellitus. Although there is evidence that long noncoding RNAs (lncRNAs) play important roles in development and disease, none have been investigated in vivo in the context of pancreas development. In this study, we demonstrate that βlinc1 (β-cell long intergenic noncoding RNA 1), a conserved lncRNA, is necessary for the specification and function of insulin-producing β cells through the coordinated regulation of a number of islet-specific transcription factors located in the genomic vicinity of βlinc1. Furthermore, deletion of βlinc1 results in defective islet development and disruption of glucose homeostasis in adult mice.
Journal articleHorikoshi M, Pasquali L, Wiltshire S, et al., 2016,
Transancestral fine-mapping of four type 2 diabetes susceptibility loci highlights potential causal regulatory mechanisms, Human Molecular Genetics, Vol: 25, Pages: 2070-2081, ISSN: 1460-2083
To gain insight into potential regulatory mechanisms through which the effects of variants at four established type 2 diabetes (T2D) susceptibility loci (CDKAL1, CDKN2A-B, IGF2BP2 and KCNQ1) are mediated, we undertook transancestral fine-mapping in 22 086 cases and 42 539 controls of East Asian, European, South Asian, African American and Mexican American descent. Through high-density imputation and conditional analyses, we identified seven distinct association signals at these four loci, each with allelic effects on T2D susceptibility that were homogenous across ancestry groups. By leveraging differences in the structure of linkage disequilibrium between diverse populations, and increased sample size, we localised the variants most likely to drive each distinct association signal. We demonstrated that integration of these genetic fine-mapping data with genomic annotation can highlight potential causal regulatory elements in T2D-relevant tissues. These analyses provide insight into the mechanisms through which T2D association signals are mediated, and suggest future routes to understanding the biology of specific disease susceptibility loci.
Journal articleDe Vas M, Ferrer J, 2016,
Journal articleGaulton KJ, Ferreira T, Lee Y, et al., 2015,
Genetic fine mapping and genomic annotation defines causal mechanisms at type 2 diabetes susceptibility loci., Nature Genetics, Vol: 47, Pages: 1415-1425, ISSN: 1546-1718
We performed fine mapping of 39 established type 2 diabetes (T2D) loci in 27,206 cases and 57,574 controls of European ancestry. We identified 49 distinct association signals at these loci, including five mapping in or near KCNQ1. 'Credible sets' of the variants most likely to drive each distinct signal mapped predominantly to noncoding sequence, implying that association with T2D is mediated through gene regulation. Credible set variants were enriched for overlap with FOXA2 chromatin immunoprecipitation binding sites in human islet and liver cells, including at MTNR1B, where fine mapping implicated rs10830963 as driving T2D association. We confirmed that the T2D risk allele for this SNP increases FOXA2-bound enhancer activity in islet- and liver-derived cells. We observed allele-specific differences in NEUROD1 binding in islet-derived cells, consistent with evidence that the T2D risk allele increases islet MTNR1B expression. Our study demonstrates how integration of genetic and genomic information can define molecular mechanisms through which variants underlying association signals exert their effects on disease.
Journal articleMiguel Escalada I, Pasquali L, Ferrer J, 2015,
In recent years, studies of cis-regulatory mechanisms have evolved from a predominant focus on promoter regions to the realization that spatial and temporal gene regulation is frequently driven by long-range enhancer clusters that operate within chromosomal compartments. This increased understanding of genome function, together with the emergence of technologies that enable whole-genome sequencing of patients’ DNAs, open the prospect of dissecting the role of cis-regulatory defects in human disease. In this review we discuss how recent epigenomic studies have provided insights into the function of transcriptional enhancers. We then present examples that illustrate how integrative genomics can help uncover enhancer sequence variants underlying Mendelian and common polygenic human disease.
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