Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Identification of proliferative and mature Î²-cells in the islet of Langerhans

ABSTRACT: Insulin-dependent diabetes is a complex multifactorial disorder characterized by loss or dysfunction of Î²-cells. Pancreatic Î²-cells differ in size, glucose responsiveness, insulin secretion and precursor cell potential1-5, thus understanding the mechanisms underlying this functional heterogeneity might allow novel regenerative approaches. Here we discovered Flattop (Fltp) as a biomarker that distinguishes proliferative from mature Î²-cells. Genetic lineage tracing revealed that these Î²-cell subpopulations react differentially to environmental changes. Upon insulin resistance Fltp- Î²-cells undergo compensatory proliferation, whereas Fltp-lineage+ Î²-cells account for islet cell hypertrophy commonly associated with cytotoxic stress. The expression of the Wnt/planar cell polarity (PCP) effector gene Fltp increases when naÃ¯ve Î²-cells cluster together to form polarized and mature three-dimensional (3D) islet mini-organs6-8. We show that dispersed early postnatal islet cells, insulinoma cells and human Î²-cells all have the intrinsic ability to form polarized pseudo-islets in 3D cultures. Compaction and polarization correlates with the induction of maturation markers and can be enhanced by Wnt/PCP pathway activation. Finally, we show that Fltp is not only a marker for mature Î²-cells, but is also functionally required for proper insulin secretion in mouse and human. We conclude that planar cell polarity and 3D architecture underlie functional Î²-cell heterogeneity and report that Fltp is a biomarker that separates proliferative from mature Î²-cells. These findings establish novel molecular underpinnings of Î²-cells and enable targeting of subpopulations for the regeneration of functional Î²-cell mass in diabetic patients. We performed gene expression microarray analysis on two FACS-sorted pancreatic islet cell populations: flattop-positive and flattop-negative.

ORGANISM(S): Mus musculus

SUBMITTER: Johannes Beckers

PROVIDER: E-GEOD-68853 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:A detailed understanding of intestinal stem cell (ISC) self-renewal and differentiation is required for better treatment options for a variety of chronic intestinal diseases, however, current models of ISC lineage hierarchy and segregation are still under debate. Here we report the identification of Lgr5+ ISCs that express Flattop (Fltp), a Wnt/planar cell polarity (PCP) reporter and effector gene. Functional analysis and lineage tracing revealed that Wnt/PCP-activated Fltp+ ISCs are primed towards either the enteroendocrine or Paneth cell lineage in vivo, while retaining self-renewal and multi-lineage capacity in vitro. Surprisingly, canonical Wnt/beta-catenin- and non-canonical Wnt/PCP-activated Lgr5+ ISCs are indistinguishable by the expression of stem-cell signature or secretory lineage-specifying genes, suggesting that lineage priming and cell-cycle exit is triggered at the post-transcriptional level by polarity cues and a switch of canonical to non-canonical Wnt signalling. Pseudotemporal ordering of targeted single-cell gene expression data allowed us to delineate the ISC differentiation path into enteroendocrine and Paneth cells. Strikingly, both lineages are directly recruited from ISCs via unipotent transition states, excluding the existence of formerly predicted bi- or multipotent secretory progenitors. Transitory cells that mature into Paneth cells are defined by label-retention and co-expression of stem cell and secretory lineage genes, indicating that these cells are the previously described Lgr5+ label-retaining cells (LRCs). Taken together, we identified the Wnt/PCP pathway as a new niche signal and polarity cue regulating stem cell fate. Active Wnt/PCP signalling represents one of the earliest events in ISC lineage priming towards the Paneth and enteroendocrine cell fate, preceding lateral inhibition and expression of secretory lineage-specifying genes. Thus, our findings provide a better understanding of the niche signals and redefine the mechanisms underlying ISC lineage hierarchy and segregation. Here we establish the Wnt/Planar cell polarity (PCP) gene Flattop (Fltp) as a unique marker for intestinal LRCs and their distinct secretory fate. We show that Fltp+ cells are characterized by a combined stem cell and secretory gene signature. A subset of Fltp+ cells is classified by label-retention and predominantly locates at position +4, indicative of quiescent stem cells. Strikingly, Fltp+ LRCs are specified by Wnt/PCP signaling in contrast to actively cycling stem cells that rely on the canonical Wnt/β-catenin pathway. In mice with disturbed Wnt/PCP signaling, the differentiation of enteroendocrine cells from LRCs is impaired. These findings establish Fltp as a novel marker for intestinal LRCs and implicate Wnt/PCP signaling in cell-cycle exit and commitment of ISCs to the secretory lineage. Taken together, we not only provide a marker to study LRCs in homeostatic and diseased conditions, but also identify the Wnt/PCP signaling pathway as a therapeutic target for colorectal cancer and metabolic disease.

Project description:Defects in blood development are a major contributor to complex congenital anomalies. Thrombocytopenia-Absent Radius (TAR) Syndrome is a rare congenital disease presenting with reduced blood platelets (megakaryocytic thrombocytopenia) and forelimb anomalies, concurrent with variable heart and kidney defects caused by hypomorphic RBM8A/Y14 gene function. RBM8A encodes a component of the ubiquitous exon junction complex involved in mRNA splicing, transport, and nonsense-mediated decay. How perturbing a general mRNA-processing factor causes the distinct phenotypes of TAR Syndrome remains unknown. Here, we connect zebrafish rbm8a perturbation to early hematopoiesis defects via attenuated planar cell polarity (PCP) signaling involved in controlling developmental cell arrangements. Combining different genetic means to reduce rbm8a function, we find a significant reduction of cd41-positive thrombocytes in hypomorphic rbm8a larvae. Transcriptomics analysis documents rbm8a-mutant zebrafish embryos already after gastrulation accumulate mRNAs with erroneously included introns, a hallmark of defective nonsense-mediated decay. Affected mRNAs include transcripts encoding components of the non-canonical Wnt pathway involved in PCP signaling, and rbm8a mutant-embryos show hallmarks of Wnt/PCP-dependent, early convergent extension defects. We establish that reduced rbm8a function synergizes with perturbations in Wnt/PCP pathway genes including wnt5b, wnt11f2, fzd7a, and vangl2. Following axis formation, rbm8a perturbation impairs the migration and architecture of the lateral plate mesoderm (LPM) that forms the hematopoietic, cardiovascular, kidney, and forelimb skeleton progenitors. Subsequently, rbm8a perturbation impairs expression of early hematopoietic/endothelial genes including runx1a, kdrl, sox7, and the megakaryocyte regulator gfi1aa. Lastly, we document similar hematopoietic defects upon loss of vangl2. Together, our data link reduced rbm8a function to LPM migration and hematopoietic defects via attenuated Wnt/PCP signaling. Our findings establish a developmental framework that connects the complex TAR Syndrome phenotypes to a potential LPM origin.

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Identification of proliferative and mature Î²-cells in the islet of Langerhans

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