A single-cell atlas of the murine pancreatic ductal tree identifies novel cell populations with potential implications in pancreas regeneration and exocrine pathogenesis.

BACKGROUND AND AIMS: Pancreatic ducts form an intricate network of tubules that secrete bicarbonate and drive acinar secretions into the duodenum. This network is formed by centroacinar cells, terminal, intercalated, intracalated ducts, and the main pancreatic duct. Ductal heterogeneity at the single-cell level has been poorly characterized; therefore, our understanding of the role of ductal cells in pancreas regeneration and exocrine pathogenesis has been hampered by the limited knowledge and unexplained diversity within the ductal network. METHODS: We used scRNA-seq to comprehensively characterize mouse ductal heterogeneity at single-cell resolution of the entire ductal epithelium from centroacinar cells to the main duct. Moreover, we used organoid cultures, injury models and pancreatic tumor samples to interrogate the role of novel ductal populations in pancreas regeneration and exocrine pathogenesis. RESULTS: We have identified the coexistence of 15 ductal populations within the healthy pancreas and characterized their organoid formation capacity and endocrine differentiation potential. Cluster isolation and subsequent culturing let us identify ductal cell populations with high organoid formation capacity and endocrine and exocrine differentiation potential in vitro, including Wnt-responsive-population, ciliated-population and FLRT3+ cells. Moreover, we have characterized the location of these novel ductal populations in healthy pancreas, chronic pancreatitis, and tumor samples. The expression of WNT-responsive, IFN-responsive and EMT-population markers increases in chronic pancreatitis and tumor samples. CONCLUSIONS: In light of our discovery of previously unidentified ductal populations, we unmask potential roles of specific ductal populations in pancreas regeneration and exocrine pathogenesis. Thus, novel lineage tracing models are needed to investigate ductal specific populations in vivo.

Regulation of ß-cell death by ADP-ribosylhydrolase ARH3 via lipid signaling in insulitis.

BACKGROUND: Lipids are regulators of insulitis and ß-cell death in type 1 diabetes development, but the underlying mechanisms are poorly understood. Here, we investigated how the islet lipid composition and downstream signaling regulate ß-cell death. METHODS: We performed lipidomics using three models of insulitis: human islets and EndoC-ßH1 ß cells treated with the pro-inflammatory cytokines interlukine-1ß and interferon-γ, and islets from pre-diabetic non-obese mice. We also performed mass spectrometry and fluorescence imaging to determine the localization of lipids and enzyme in islets. RNAi, apoptotic assay, and qPCR were performed to determine the role of a specific factor in lipid-mediated cytokine signaling. RESULTS: Across all three models, lipidomic analyses showed a consistent increase of lysophosphatidylcholine species and phosphatidylcholines with polyunsaturated fatty acids and a reduction of triacylglycerol species. Imaging assays showed that phosphatidylcholines with polyunsaturated fatty acids and their hydrolyzing enzyme phospholipase PLA2G6 are enriched in islets. In downstream signaling, omega-3 fatty acids reduce cytokine-induced ß-cell death by improving the expression of ADP-ribosylhydrolase ARH3. The mechanism involves omega-3 fatty acid-mediated reduction of the histone methylation polycomb complex PRC2 component Suz12, upregulating the expression of Arh3, which in turn decreases cell apoptosis. CONCLUSIONS: Our data provide insights into the change of lipidomics landscape in ß cells during insulitis and identify a protective mechanism by omega-3 fatty acids. Video Abstract.

UMI4Cats: an R package to analyze chromatin contact profiles obtained by UMI-4C.

MOTIVATION: UMI-4C, a technique that combines chromosome conformation capture (4C) and unique molecular identifiers (UMI), is widely used to profile and quantitatively compare targeted chromosomal contact profiles. The analysis of UMI-4C experiments presents several computational challenges, including the removal of the PCR duplication bias and the identification of differential chromatin contacts. RESULTS: We have developed UMI4Cats (UMI-4C Analysis Turned Simple), an R package that facilitates processing, analyzing and visualizing of data obtained by UMI-4C experiments. AVAILABILITY AND IMPLEMENTATION: UMI4Cats is implemented as an R package supported on Linux, MacOS and MS Windows. UMI4Cats is available from Bioconductor (https://www.bioconductor.org/packages/release/bioc/html/UMI4Cats.html) and GitHub (https://github.com/Pasquali-lab/UMI4Cats). SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

miR-378a regulates keratinocyte responsiveness to interleukin-17A in psoriasis.

BACKGROUND: Psoriasis is an immune-mediated inflammatory skin disease, in which an interplay between infiltrating immune cells and keratinocytes sustains chronic skin inflammation. Interleukin (IL)-17A is a key inflammatory cytokine in psoriasis and its main cellular targets are keratinocytes. OBJECTIVES: To explore the role of miR-378a in psoriasis. METHODS: Keratinocytes obtained from psoriatic skin and healthy epidermis were separated by magnetic sorting, and the expression of miR-378a was analysed by quantitative polymerase chain reaction. The regulation and function of miR-378a was studied using primary human keratinocytes. The expression of miR-378a was modulated by synthetic mimics, and nuclear factor kappa B (NF-κB) activity and transcriptomic changes were studied. Synthetic miR-378a was delivered to mouse skin in conjunction with induction of psoriasiform skin inflammation by imiquimod. RESULTS: We show that miR-378a is induced by IL-17A in keratinocytes through NF-κB, C/EBP-ß and IκBζ and that it is overexpressed in psoriatic epidermis. In cultured keratinocytes, ectopic expression of miR-378a resulted in the nuclear translocation of p65 and enhanced NF-κB-driven promoter activity even in the absence of inflammatory stimuli. Moreover, miR-378a potentiated the effect of IL-17A on NF-κB nuclear translocation and downstream activation of the NF-κB pathway. Finally, injection of miR-378a into mouse skin augmented psoriasis-like skin inflammation with increased epidermal proliferation and induction of inflammatory mediators. Mechanistically, miR-378a acts as a suppressor of NFKBIA/IκBζ, an important negative regulator of the NF-κB pathway in keratinocytes. CONCLUSIONS: Collectively, our findings identify miR-378a as an amplifier of IL-17A-induced NF-κB signalling in keratinocytes and suggest that increased miR-378a levels contribute to the amplification of IL-17A-driven skin inflammation in psoriasis.

Cross-talk between IFN-γ and TWEAK through miR-149 amplifies skin inflammation in psoriasis.

BACKGROUND: Psoriasis is a chronic inflammatory skin disease with disturbed interplay between immune cells and keratinocytes. A strong IFN-γ signature is characteristic for psoriasis skin, but the role of IFN-γ has been elusive. MicroRNAs are short RNAs regulating gene expression. OBJECTIVE: Our aim was to investigate the role of miR-149 in psoriasis and in the inflammatory responses of keratinocytes. METHODS: miR-149 expression was measured by quantitative RT-PCR in keratinocytes isolated from healthy skin and lesional and nonlesional psoriasis skin. Synthetic miR-149 was injected intradermally into the back skin of mice, and imiquimod was applied to induce psoriasis-like skin inflammation, which was then evaluated at the morphologic, histologic, and molecular levels. miR-149 was transiently overexpressed or inhibited in keratinocytes in combination with IFN-γ- and/or TNF-related weak inducer of apoptosis (TWEAK)-treatment. RESULTS: Here we report a microRNA-mediated mechanism by which IFN-γ primes keratinocytes to inflammatory stimuli. Treatment with IFN-γ results in a rapid and long-lasting suppression of miR-149 in keratinocytes. Depletion of miR-149 in keratinocytes leads to widespread transcriptomic changes and induction of inflammatory mediators with enrichment of the TWEAK pathway. We show that IFN-γ-mediated suppression of miR-149 leads to amplified inflammatory responses to TWEAK. TWEAK receptor (TWEAKR/Fn14) is identified as a novel direct target of miR-149. The in vivo relevance of this pathway is supported by decreased miR-149 expression in psoriasis keratinocytes, as well as by the protective effect of synthetic miR-149 in the imiquimod-induced mouse model of psoriasis. CONCLUSION: Our data define a new mechanism, in which IFN-γ primes keratinocytes for TWEAK-induced inflammatory responses through suppression of miR-149, promoting skin inflammation.

The ß-Cell Genomic Landscape in T1D: Implications for Disease Pathogenesis.

PURPOSE OF REVIEW: Type 1 diabetes (T1D) develops as a consequence of a combination of genetic predisposition and environmental factors. Combined, these events trigger an autoimmune disease that results in progressive loss of pancreatic ß cells, leading to insulin deficiency. This article reviews the current knowledge on the genetics of T1D with a specific focus on genetic variation in pancreatic islet regulatory networks and its implication to T1D risk and disease development. RECENT FINDINGS: Accumulating evidence suggest an active role of ß cells in T1D pathogenesis. Based on such observation several studies aimed in mapping T1D risk variants acting at the ß cell level. Such studies unravel T1D risk loci shared with type 2 diabetes (T2D) and T1D risk variants potentially interfering with ß-cell responses to external stimuli. The characterization of regulatory genomics maps of disease-relevant states and cell types can be used to elucidate the mechanistic role of ß cells in the pathogenesis of T1D.

The Keratinocyte Transcriptome in Psoriasis: Pathways Related to Immune Responses, Cell Cycle and Keratinization.

Psoriasis is a common immune-mediated disease resulting from altered cross-talk between keratinocytes and immune cells. Previous transcriptomic studies have identified thousands of deregulated genes in psoriasis skin; however, the transcriptomic changes confined to the epidermal compartment remained poorly characterized. The aim of this study was to characterize the transcriptomic landscape of psoriatic keratinocytes, using sorted CD45neg epidermal cells. Genes with functions in innate immunity, type I interferon response, cell cycle and keratinization were enriched among deregulated genes in psoriatic keratinocytes. Gene set enrichment analysis indicated the dominance of interleukin (IL)-22/IL-17A signatures in the epidermal psoriasis-signature. A set of deregulated genes overlapped with psoriasis-associated genetic regions, suggesting that genetic variations affecting gene expression in keratinocytes contribute to susceptibility to psoriasis. Several psoriasis-susceptibility genes, which were previously believed to be expressed preferentially or exclusively in immune cells, were identified as having altered expression in psoriatic keratinocytes. These results highlight the role of keratinocytes in the pathogenesis of psoriasis, and indicate that both genetic factors and an inflammatory microenvironment contribute to epidermal alterations in psoriasis.

Transancestral fine-mapping of four type 2 diabetes susceptibility loci highlights potential causal regulatory mechanisms.

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.

A single-cell atlas of the murine pancreatic ductal tree identifies novel cell populations with potential implications in pancreas regeneration and exocrine pathogenesis.

Background and aims: Pancreatic ducts form an intricate network of tubules that secrete bicarbonate and drive acinar secretions into the duodenum. This network is formed by centroacinar cells, terminal, intercalated, intracalated ducts, and the main pancreatic duct. Ductal heterogeneity at the single-cell level has been poorly characterized; therefore, our understanding of the role of ductal cells in pancreas regeneration and exocrine pathogenesis has been hampered by the limited knowledge and unexplained diversity within the ductal network. Methods: We used scRNA-seq to comprehensively characterize mouse ductal heterogeneity at single-cell resolution of the entire ductal epithelium from centroacinar cells to the main duct. Moreover, we used organoid cultures, injury models and pancreatic tumor samples to interrogate the role of novel ductal populations in pancreas regeneration and exocrine pathogenesis. Results: We have identified the coexistence of 15 ductal populations within the healthy pancreas and characterized their organoid formation capacity and endocrine differentiation potential. Cluster isolation and subsequent culturing let us identify ductal cell populations with high organoid formation capacity and endocrine and exocrine differentiation potential in vitro , including Wnt-responsive-population, ciliated-population and FLRT3 + cells. Moreover, we have characterized the location of these novel ductal populations in healthy pancreas, chronic pancreatitis, and tumor samples, highlighting a putative role of WNT-responsive, IFN-responsive and EMT-populations in pancreatic exocrine pathogenesis as their expression increases in chronic pancreatitis and PanIN lesions. Conclusions: In light of our discovery of previously unidentified ductal populations, we unmask the potential roles of specific ductal populations in pancreas regeneration and exocrine pathogenesis.

The Long Noncoding RNA LINC00958 Is Induced in Psoriasis Epidermis and Modulates Epidermal Proliferation.

Psoriasis is a common, immune-mediated skin disease characterized by epidermal hyperproliferation and chronic skin inflammation. Long noncoding RNAs are >200 nucleotide-long transcripts that possess important regulatory functions. To date, little is known about the contribution of long noncoding RNAs to psoriasis. In this study, we identify LINC00958 as a long noncoding RNA overexpressed in keratinocytes (KCs) from psoriasis skin lesions, in a transcriptomic screen performed on KCs sorted from psoriasis and healthy skin. Increased levels of LINC00958 in psoriasis KCs were confirmed by RT-qPCR and single-molecule in situ hybridization. Confocal microscopy and analysis of subcellular fractions showed that LINC00958 is mainly localized in the cytoplasm of KCs. IL-17A, a key psoriasis cytokine, induced LINC00958 in KCs through C/EBP-ß and the p38 pathway. The inhibition of LINC00958 led to decreased proliferation as measured by Ki-67 expression, live cell analysis imaging, and 5-ethynyl-2-deoxyuridine assays. Transcriptomic analysis of LINC00958-depleted KCs revealed enrichment of proliferation- and cell cycle‒related genes among differentially expressed transcripts. Moreover, LINC00958 depletion led to decreased basal and IL-17A‒induced phosphorylation of p38. Furthermore, IL-17A‒induced KC proliferation was counteracted by the inhibition of LINC00958. In summary, our data support a role for the IL-17A‒induced long noncoding RNA, LINC00958, in the pathological circuits of psoriasis by reinforcing IL-17A‒induced epidermal hyperproliferation.

Direct reprogramming of human fibroblasts into insulin-producing cells using transcription factors.

Direct lineage reprogramming of one somatic cell into another without transitioning through a progenitor stage has emerged as a strategy to generate clinically relevant cell types. One cell type of interest is the pancreatic insulin-producing ß cell whose loss and/or dysfunction leads to diabetes. To date it has been possible to create ß-like cells from related endodermal cell types by forcing the expression of developmental transcription factors, but not from more distant cell lineages like fibroblasts. In light of the therapeutic benefits of choosing an accessible cell type as the cell of origin, in this study we set out to analyze the feasibility of transforming human skin fibroblasts into ß-like cells. We describe how the timed-introduction of five developmental transcription factors (Neurog3, Pdx1, MafA, Pax4, and Nkx2-2) promotes conversion of fibroblasts toward a ß-cell fate. Reprogrammed cells exhibit ß-cell features including ß-cell gene expression and glucose-responsive intracellular calcium mobilization. Moreover, reprogrammed cells display glucose-induced insulin secretion in vitro and in vivo. This work provides proof-of-concept of the capacity to make insulin-producing cells from human fibroblasts via transcription factor-mediated direct reprogramming.

MacroH2As regulate enhancer-promoter contacts affecting enhancer activity and sensitivity to inflammatory cytokines.

MacroH2A histone variants have a function in gene regulation that is poorly understood at the molecular level. We report that macroH2A1.2 and macroH2A2 modulate the transcriptional ground state of cancer cells and how they respond to inflammatory cytokines. Removal of macroH2A1.2 and macroH2A2 in hepatoblastoma cells affects the contact frequency of promoters and distal enhancers coinciding with changes in enhancer activity or preceding them in response to the cytokine tumor necrosis factor alpha. Although macroH2As regulate genes in both directions, they globally facilitate the nuclear factor κB (NF-κB)-mediated response. In contrast, macroH2As suppress the response to the pro-inflammatory cytokine interferon gamma. MacroH2A2 has a stronger contribution to gene repression than macroH2A1.2. Taken together, our results suggest that macroH2As have a role in regulating the response of cancer cells to inflammatory signals on the level of chromatin structure. This is likely relevant for the interaction of cancer cells with immune cells of their microenvironment.

GATA4 induces liver fibrosis regression by deactivating hepatic stellate cells.

In response to liver injury, hepatic stellate cells activate and acquire proliferative and contractile features. The regression of liver fibrosis appears to involve the clearance of activated hepatic stellate cells, either by apoptosis or by reversion toward a quiescent-like state, a process called deactivation. Thus, deactivation of active hepatic stellate cells has emerged as a novel and promising therapeutic approach for liver fibrosis. However, our knowledge of the master regulators involved in the deactivation and/or activation of fibrotic hepatic stellate cells is still limited. The transcription factor GATA4 has been previously shown to play an important role in embryonic hepatic stellate cell quiescence. In this work, we show that lack of GATA4 in adult mice caused hepatic stellate cell activation and, consequently, liver fibrosis. During regression of liver fibrosis, Gata4 was reexpressed in deactivated hepatic stellate cells. Overexpression of Gata4 in hepatic stellate cells promoted liver fibrosis regression in CCl4-treated mice. GATA4 induced changes in the expression of fibrogenic and antifibrogenic genes, promoting hepatic stellate cell deactivation. Finally, we show that GATA4 directly repressed EPAS1 transcription in hepatic stellate cells and that stabilization of the HIF2α protein in hepatic stellate cells leads to liver fibrosis.

Pancreatic ß-cells in type 1 and type 2 diabetes mellitus: different pathways to failure.

Loss of functional ß-cell mass is the key mechanism leading to the two main forms of diabetes mellitus - type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Understanding the mechanisms behind ß-cell failure is critical to prevent or revert disease. Basic pathogenic differences exist in the two forms of diabetes mellitus; T1DM is immune mediated and T2DM is mediated by metabolic mechanisms. These mechanisms differentially affect early ß-cell dysfunction and eventual fate. Over the past decade, major advances have been made in the field, mostly delivered by studies on ß-cells in human disease. These advances include studies of islet morphology and human ß-cell gene expression in T1DM and T2DM, the identification and characterization of the role of T1DM and T2DM candidate genes at the ß-cell level and the endoplasmic reticulum stress signalling that contributes to ß-cell failure in T1DM (mostly IRE1 driven) and T2DM (mostly PERK-eIF2α dependent). Here, we review these new findings, focusing on studies performed on human ß-cells or on samples obtained from patients with diabetes mellitus.

Co-regulation of the antagonistic RepoMan:Aurora-B pair in proliferating cells.

Chromosome segregation during mitosis is antagonistically regulated by the Aurora-B kinase and RepoMan (recruits PP1 onto mitotic chromatin at anaphase)-associated phosphatases PP1/PP2A. Aurora B is overexpressed in many cancers but, surprisingly, this only rarely causes lethal aneuploidy. Here we show that RepoMan abundance is regulated by the same mechanisms that control Aurora B, including FOXM1-regulated expression and proteasomal degradation following ubiquitination by APC/C-CDH1 or SCFFBXW7. The deregulation of these mechanisms can account for the balanced co-overexpression of Aurora B and RepoMan in many cancers, which limits chromosome segregation errors. In addition, Aurora B and RepoMan independently promote cancer cell proliferation by reducing checkpoint--induced cell-cycle arrest during interphase. The co-up-regulation of RepoMan and Aurora B in tumors is inversely correlated with patient survival, underscoring its potential importance for tumor progression. Finally, we demonstrate that high RepoMan levels sensitize cancer cells to Aurora-B inhibitors. Hence, the co-up-regulation of RepoMan and Aurora B is associated with tumor aggressiveness but also exposes a vulnerable target for therapeutic intervention.

A comprehensive analysis of coding and non-coding transcriptomic changes in cutaneous squamous cell carcinoma.

Cutaneous Squamous Cell Carcinoma (cSCC) is the most common and fastest-increasing cancer with metastatic potential. Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are novel regulators of gene expression. To identify mRNAs, lncRNAs and circRNAs, which can be involved in cSCC, RNA-seq was performed on nine cSCCs and seven healthy skin samples. Representative transcripts were validated by NanoString nCounter assays using an extended cohort, which also included samples from pre-cancerous skin lesions (actinic keratosis). 5,352 protein-coding genes, 908 lncRNAs and 55 circular RNAs were identified to be differentially expressed in cSCC. Targets of 519 transcription factors were enriched among differentially expressed genes, 105 of which displayed altered level in cSCCs, including fundamental regulators of skin development (MYC, RELA, ETS1, TP63). Pathways related to cell cycle, apoptosis, inflammation and epidermal differentiation were enriched. In addition to known oncogenic lncRNAs (PVT1, LUCAT1, CASC9), a set of skin-specific lncRNAs were were identified to be dysregulated. A global downregulation of circRNAs was observed in cSCC, and novel skin-enriched circRNAs, circ_IFFO2 and circ_POF1B, were identified and validated. In conclusion, a reference set of coding and non-coding transcripts were identified in cSCC, which may become potential therapeutic targets or biomarkers.

An integrated multi-omics approach identifies the landscape of interferon-α-mediated responses of human pancreatic beta cells.

Interferon-α (IFNα), a type I interferon, is expressed in the islets of type 1 diabetic individuals, and its expression and signaling are regulated by T1D genetic risk variants and viral infections associated with T1D. We presently characterize human beta cell responses to IFNα by combining ATAC-seq, RNA-seq and proteomics assays. The initial response to IFNα is characterized by chromatin remodeling, followed by changes in transcriptional and translational regulation. IFNα induces changes in alternative splicing (AS) and first exon usage, increasing the diversity of transcripts expressed by the beta cells. This, combined with changes observed on protein modification/degradation, ER stress and MHC class I, may expand antigens presented by beta cells to the immune system. Beta cells also up-regulate the checkpoint proteins PDL1 and HLA-E that may exert a protective role against the autoimmune assault. Data mining of the present multi-omics analysis identifies two compound classes that antagonize IFNα effects on human beta cells.

Association of alleles at polymorphic sites in the Osteopontin encoding gene in young type 1 diabetic patients.

The Osteopontin (OPN) encoding gene, SPP1, can be considered as a candidate for genetic susceptibility to type 1 diabetes (T1D) because of its known function in immune response and inflammation. This work aimed to evaluate the role of SPP1 gene in susceptibility to T1D. Patients (238: 130 male, 108 female) and unaffected adult control individuals (137: 68 males and 69 females) have been genotyped for three variants in the SPP1 gene: -156 (G/GG) and -66 (T/G) in the promoter and a biallelic ins/del variant (TG/TGTG) at +245 in the first intron. The G allele at the -66 SNP had significantly higher frequency in controls than T1D patients. Interestingly, case-control comparison in males showed no significant association, whereas the association was confirmed in females. These results suggest that SPP1 can play a role as susceptibility gene, possibly by a sex-specific mechanism acting in the autoimmune process.

The impact of proinflammatory cytokines on the ß-cell regulatory landscape provides insights into the genetics of type 1 diabetes.

The early stages of type 1 diabetes (T1D) are characterized by local autoimmune inflammation and progressive loss of insulin-producing pancreatic ß cells. Here we show that exposure to proinflammatory cytokines reveals a marked plasticity of the ß-cell regulatory landscape. We expand the repertoire of human islet regulatory elements by mapping stimulus-responsive enhancers linked to changes in the ß-cell transcriptome, proteome and three-dimensional chromatin structure. Our data indicate that the ß-cell response to cytokines is mediated by the induction of new regulatory regions as well as the activation of primed regulatory elements prebound by islet-specific transcription factors. We find that T1D-associated loci are enriched with newly mapped cis-regulatory regions and identify T1D-associated variants disrupting cytokine-responsive enhancer activity in human ß cells. Our study illustrates how ß cells respond to a proinflammatory environment and implicate a role for stimulus response islet enhancers in T1D.