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Identification of a bipotential precursor cell in hepatic cell lines derived from transgenic mice expressing cyto-Met in the liver.

Spagnoli FM, Amicone L, Tripodi M, Weiss MC - J. Cell Biol. (1998)

Bottom Line: Palmate cells show none of these properties.Derivation of epithelial from palmate cells is confirmed by characterization of the progeny of individually fished cells.The clonal isolation of the palmate cell, an immortalized nontransformed bipotential cell that does not yet express the liver-enriched transcription factors and is a precursor of the epithelial-hepatocyte in MMH lines, provides a new tool for the study of mechanisms controlling liver development.

View Article: PubMed Central - PubMed

Affiliation: Unité de Génétique de la Différenciation, URA 1773 du Centre National de la Recherche Scientifique, Institut Pasteur, 75724 Paris Cedex 15, France.

ABSTRACT
Met murine hepatocyte (MMH) lines were established from livers of transgenic mice expressing constitutively active human Met. These lines harbor two cell types: epithelial cells resembling the parental populations and flattened cells with multiple projections and a dispersed growth habit that are designated palmate. Epithelial cells express the liver-enriched transcription factors HNF4 and HNF1alpha, and proteins associated with epithelial cell differentiation. Treatments that modulate their differentiation state, including acidic FGF, induce hepatic functions. Palmate cells show none of these properties. However, they can differentiate along the hepatic cell lineage, giving rise to: (a) epithelial cells that express hepatic transcription factors and are competent to express hepatic functions; (b) bile duct-like structures in three-dimensional Matrigel cultures. Derivation of epithelial from palmate cells is confirmed by characterization of the progeny of individually fished cells. Furthermore, karyotype analysis confirms the direction of the phenotypic transition: palmate cells are diploid and the epithelial cells are hypotetraploid. The clonal isolation of the palmate cell, an immortalized nontransformed bipotential cell that does not yet express the liver-enriched transcription factors and is a precursor of the epithelial-hepatocyte in MMH lines, provides a new tool for the study of mechanisms controlling liver development.

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Schematic representation of the different phenotypic  states of the MMH lines and their clones, and spontaneous or induced transitions. The discontinuous arrow indicates a spontaneous transition; continuous two- and one-headed arrows indicate  reversible and irreversible phenotypic modulations, respectively.  Abbreviations used are the same as those in Fig. 6.
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Figure 8: Schematic representation of the different phenotypic states of the MMH lines and their clones, and spontaneous or induced transitions. The discontinuous arrow indicates a spontaneous transition; continuous two- and one-headed arrows indicate reversible and irreversible phenotypic modulations, respectively. Abbreviations used are the same as those in Fig. 6.

Mentions: A limitation to the study of liver development has been the absence of lines of nontransformed precursor cells that can differentiate into hepatocytes in culture, and that possesses sufficient proliferative potential that clonal progeny can be isolated and characterized. The immortalized palmate cell may fill this gap. The palmate cell goes through at least two stages when differentiating in vitro, whether the transition is spontaneous or induced. Fig. 8 presents in a schematic fashion these transitions, the factors that induce them, and the properties of cells of the different stages. Characterization of the MMH clones revealed that there must exist at least two, and possibly three, classes of epithelial cells, going from the most to the least differentiated: (a) the most differentiated cells are hypotetraploid, polarized, and express the LETF as well as the liver functions in the absence of any stimulus. This is the only phenotype observed for the D3 cells and its clones. (b) An intermediate class is composed of hypotetraploid cells that display a well-polarized epithelial phenotype and express HNF1α and HNF4 but fail to express hepatic functions unless stimulated to do so. Cells of this class present an uncoupled phenotype (expression of HNF1α and HNF4 concomitant with absence of hepatic functions), recently described for some rat hepatoma variants (Chaya et al., 1997). (c) Finally, there is probably a transitory epithelial cell population that still retains a diploid chromosome number. Existence of this hypothetical third class is suggested by the facts that (a) 75% of the E14 parental population is diploid while more than half of the progeny clones are epithelial, and (b) some of the epithelial clones present bimodal karyotypes. Among the three MMH lines analyzed, only the D3 line is devoid of diploid cells and fails to give rise to palmate colonies upon cloning. A possible explanation for the absence of palmate cells from the D3 line is their depletion in favor of epithelial progeny. Alternatively, the initial immortalized D3 cell could have been epithelial rather than palmate. Further study of the events underlying emergence of immortalized transgenic liver cells should provide an answer to this question.


Identification of a bipotential precursor cell in hepatic cell lines derived from transgenic mice expressing cyto-Met in the liver.

Spagnoli FM, Amicone L, Tripodi M, Weiss MC - J. Cell Biol. (1998)

Schematic representation of the different phenotypic  states of the MMH lines and their clones, and spontaneous or induced transitions. The discontinuous arrow indicates a spontaneous transition; continuous two- and one-headed arrows indicate  reversible and irreversible phenotypic modulations, respectively.  Abbreviations used are the same as those in Fig. 6.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2132947&req=5

Figure 8: Schematic representation of the different phenotypic states of the MMH lines and their clones, and spontaneous or induced transitions. The discontinuous arrow indicates a spontaneous transition; continuous two- and one-headed arrows indicate reversible and irreversible phenotypic modulations, respectively. Abbreviations used are the same as those in Fig. 6.
Mentions: A limitation to the study of liver development has been the absence of lines of nontransformed precursor cells that can differentiate into hepatocytes in culture, and that possesses sufficient proliferative potential that clonal progeny can be isolated and characterized. The immortalized palmate cell may fill this gap. The palmate cell goes through at least two stages when differentiating in vitro, whether the transition is spontaneous or induced. Fig. 8 presents in a schematic fashion these transitions, the factors that induce them, and the properties of cells of the different stages. Characterization of the MMH clones revealed that there must exist at least two, and possibly three, classes of epithelial cells, going from the most to the least differentiated: (a) the most differentiated cells are hypotetraploid, polarized, and express the LETF as well as the liver functions in the absence of any stimulus. This is the only phenotype observed for the D3 cells and its clones. (b) An intermediate class is composed of hypotetraploid cells that display a well-polarized epithelial phenotype and express HNF1α and HNF4 but fail to express hepatic functions unless stimulated to do so. Cells of this class present an uncoupled phenotype (expression of HNF1α and HNF4 concomitant with absence of hepatic functions), recently described for some rat hepatoma variants (Chaya et al., 1997). (c) Finally, there is probably a transitory epithelial cell population that still retains a diploid chromosome number. Existence of this hypothetical third class is suggested by the facts that (a) 75% of the E14 parental population is diploid while more than half of the progeny clones are epithelial, and (b) some of the epithelial clones present bimodal karyotypes. Among the three MMH lines analyzed, only the D3 line is devoid of diploid cells and fails to give rise to palmate colonies upon cloning. A possible explanation for the absence of palmate cells from the D3 line is their depletion in favor of epithelial progeny. Alternatively, the initial immortalized D3 cell could have been epithelial rather than palmate. Further study of the events underlying emergence of immortalized transgenic liver cells should provide an answer to this question.

Bottom Line: Palmate cells show none of these properties.Derivation of epithelial from palmate cells is confirmed by characterization of the progeny of individually fished cells.The clonal isolation of the palmate cell, an immortalized nontransformed bipotential cell that does not yet express the liver-enriched transcription factors and is a precursor of the epithelial-hepatocyte in MMH lines, provides a new tool for the study of mechanisms controlling liver development.

View Article: PubMed Central - PubMed

Affiliation: Unité de Génétique de la Différenciation, URA 1773 du Centre National de la Recherche Scientifique, Institut Pasteur, 75724 Paris Cedex 15, France.

ABSTRACT
Met murine hepatocyte (MMH) lines were established from livers of transgenic mice expressing constitutively active human Met. These lines harbor two cell types: epithelial cells resembling the parental populations and flattened cells with multiple projections and a dispersed growth habit that are designated palmate. Epithelial cells express the liver-enriched transcription factors HNF4 and HNF1alpha, and proteins associated with epithelial cell differentiation. Treatments that modulate their differentiation state, including acidic FGF, induce hepatic functions. Palmate cells show none of these properties. However, they can differentiate along the hepatic cell lineage, giving rise to: (a) epithelial cells that express hepatic transcription factors and are competent to express hepatic functions; (b) bile duct-like structures in three-dimensional Matrigel cultures. Derivation of epithelial from palmate cells is confirmed by characterization of the progeny of individually fished cells. Furthermore, karyotype analysis confirms the direction of the phenotypic transition: palmate cells are diploid and the epithelial cells are hypotetraploid. The clonal isolation of the palmate cell, an immortalized nontransformed bipotential cell that does not yet express the liver-enriched transcription factors and is a precursor of the epithelial-hepatocyte in MMH lines, provides a new tool for the study of mechanisms controlling liver development.

Show MeSH