title: Cell-autonomous and signal-dependent expression of liver and intestine marker genes in pluripotent precursor cells from Xenopus embryos.
abstract: Early regulatory events in respect to the embryonic development of the vertebrate liver are only poorly defined. A better understanding of the gene network that mediates the formation of hepatocytes from pluripotent embryonic precursor cells may help to establish in vitro protocols for hepatocyte differentiation. Here, we describe our first attempts to make use of early embryonic explants from the amphibian Xenopus laevis in order to address these questions. We have identified several novel embryonic liver and intestine marker genes in a random expression pattern screen with cDNA libraries derived from the embryonic liver anlage and from the adult liver of Xenopus laevis. Based on their embryonic expression characteristics, these genes, together with the previously known ones, can be categorized into four different groups: the liver specific group (LS), the liver and intestine group A (LIA), the liver and intestine group B (LIB), and the intestine specific group (IS). Dissociation of endodermal explants isolated from early neurula stage embryos reveals that all genes in the LIB and IS groups are expressed in a cell-autonomous manner. In contrast, expression of genes in the LS and LIA groups requires cell-cell interactions. The regular temporal expression profile of genes in all four groups is mimicked in ectodermal explants from early embryos, reprogrammed by co-injection of VegT and beta-catenin mRNAs. FGF signaling is found to be required for the induction of liver specific marker (LS group) gene expression in the same system.
authors.affiliation: Abteilung Entwicklungsbiochemie, Institut fur Biochemie und Molekulare Zellbiologie, Georg-August-Universität Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
authors.forename: Yonglong
authors.initials: Y
authors.lastname: Chen
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jürgens
authors.forename: Thomas
authors.initials: T
authors.lastname: Hollemann
authors.forename: Maike
authors.initials: M
authors.lastname: Claussen
authors.forename: Giuliano
authors.initials: G
authors.lastname: Ramadori
authors.forename: Tomas
authors.initials: T
authors.lastname: Pieler
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D003598:Cytoskeletal Proteins / Q000235:genetics; D004625:Embryo, Nonmammalian; D004707:Endoderm / Q000166:cytology / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D007422:Intestines / Q000502:physiology*; D008099:Liver / Q000196:embryology / Q000502:physiology*; D008845:Microinjections; D039904:Pluripotent Stem Cells / Q000502:physiology*; D012333:RNA, Messenger; D015398:Signal Transduction / Q000502:physiology; D020825:T-Box Domain Proteins / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics; D051176:beta Catenin
chemical_list: C495266:CTNNB1 protein, Xenopus; D003598:Cytoskeletal Proteins; D005819:Genetic Markers; D012333:RNA, Messenger; D020825:T-Box Domain Proteins; D015534:Trans-Activators; C103966:VegT protein, Xenopus; D029867:Xenopus Proteins; D051176:beta Catenin; D005346:Fibroblast Growth Factors