Virginie Nepote

Bio: Virginie Nepote is an academic researcher from University of Geneva. The author has contributed to research in topics: Transgene & Enteroendocrine cell. The author has an hindex of 6, co-authored 6 publications receiving 1183 citations.

Conversion of adult pancreatic α-cells to β-cells after extreme β-cell loss

Abstract: Pancreatic insulin-producing beta-cells have a long lifespan, such that in healthy conditions they replicate little during a lifetime. Nevertheless, they show increased self-duplication after increased metabolic demand or after injury (that is, beta-cell loss). It is not known whether adult mammals can differentiate (regenerate) new beta-cells after extreme, total beta-cell loss, as in diabetes. This would indicate differentiation from precursors or another heterologous (non-beta-cell) source. Here we show beta-cell regeneration in a transgenic model of diphtheria-toxin-induced acute selective near-total beta-cell ablation. If given insulin, the mice survived and showed beta-cell mass augmentation with time. Lineage-tracing to label the glucagon-producing alpha-cells before beta-cell ablation tracked large fractions of regenerated beta-cells as deriving from alpha-cells, revealing a previously disregarded degree of pancreatic cell plasticity. Such inter-endocrine spontaneous adult cell conversion could be harnessed towards methods of producing beta-cells for diabetes therapies, either in differentiation settings in vitro or in induced regeneration.

Pancreatic cell lineage analyses in mice.

Abstract: Considerable knowledge of the ontogeny of the endocrine pancreas has been gained in recent years, mainly through the use of two complementary genetic approaches in transgenic mice: gene inactivation or overexpression (to assess gene function) and genetic labeling of precursor cells (to determine cell lineages). In recent years, in vivo Cre/loxP-based direct cell tracing experiments show that (i) all pancreatic cells differentiate from pdx1-expressing precursors, (ii) p48 is involved in the exocrine and endocrine pancreatic lineages, (iii) islet endocrine cells derive from ngn3-expressing progenitor cells, and (iv) insulin cells do not derive from glucagon- expressing progenitors. Lineage analyses allow the identification of progenitor cells from which mature cell types differentiate. Once identified, such progenitors can be labeled and isolated, and their differentiation and gene expression profiles studied in vitro. Understanding pancreatic cell lineages is highly relevant for future cell replacement therapies in diabetic patients, helping to define the identity of putative (endodermal) pancreatic stem cells.

An amylase/cre transgene marks the whole endoderm but the primordia of liver and ventral pancreas

Abstract: Mice bearing a Cre-encoding transgene driven by a compound [SV40 small t antigen/mousealpha-amylase-2] promoter expressed the recombinase at early developmental stages broadly in the embryonic endoderm before the pancreas and lungs begin to outgrow, but not in other germ layers, as determined indirectly by beta-galactosidase and YFP reporter activity, indicating that the transgene is in fact an endodermic marker. Interestingly, the liver and ventral pancreas were excluded from this expression pattern, denoting that the chimerical alpha-amylase-2 promoter was not active in the anterior leading edge of the endoderm (the presumptive region from which liver and ventral pancreas form). These transgenics thus confirm, among other findings, that dorsal and ventral pancreatic primordia have different intrinsic transcriptional capabilities. In conclusion, we have generated a new transgenic mouse that should be useful to target endoderm at early stages, without affecting the liver or ventral pancreas before embryonic day E12.5.

Production of pancreatic hormone–expressing endocrine cells from human embryonic stem cells

Abstract: Of paramount importance for the development of cell therapies to treat diabetes is the production of sufficient numbers of pancreatic endocrine cells that function similarly to primary islets We have developed a differentiation process that converts human embryonic stem (hES) cells to endocrine cells capable of synthesizing the pancreatic hormones insulin, glucagon, somatostatin, pancreatic polypeptide and ghrelin This process mimics in vivo pancreatic organogenesis by directing cells through stages resembling definitive endoderm, gut-tube endoderm, pancreatic endoderm and endocrine precursor--en route to cells that express endocrine hormones The hES cell-derived insulin-expressing cells have an insulin content approaching that of adult islets Similar to fetal beta-cells, they release C-peptide in response to multiple secretory stimuli, but only minimally to glucose Production of these hES cell-derived endocrine cells may represent a critical step in the development of a renewable source of cells for diabetes cell therapy

Mechanisms of Development

Abstract: Analysis of Development Edited by Prof Benjamin H Willier, Prof Paul A Weiss and Prof Viktor Hamburger Pp xii + 735 (Philadelphia and London: W B Saunders Company, 1955) 105s

Conversion of adult pancreatic α-cells to β-cells after extreme β-cell loss

Abstract: Pancreatic insulin-producing beta-cells have a long lifespan, such that in healthy conditions they replicate little during a lifetime. Nevertheless, they show increased self-duplication after increased metabolic demand or after injury (that is, beta-cell loss). It is not known whether adult mammals can differentiate (regenerate) new beta-cells after extreme, total beta-cell loss, as in diabetes. This would indicate differentiation from precursors or another heterologous (non-beta-cell) source. Here we show beta-cell regeneration in a transgenic model of diphtheria-toxin-induced acute selective near-total beta-cell ablation. If given insulin, the mice survived and showed beta-cell mass augmentation with time. Lineage-tracing to label the glucagon-producing alpha-cells before beta-cell ablation tracked large fractions of regenerated beta-cells as deriving from alpha-cells, revealing a previously disregarded degree of pancreatic cell plasticity. Such inter-endocrine spontaneous adult cell conversion could be harnessed towards methods of producing beta-cells for diabetes therapies, either in differentiation settings in vitro or in induced regeneration.