title: Ligand/receptor signaling threshold (LIST) model accounts for gp130-mediated embryonic stem cell self-renewal responses to LIF and HIL-6.
abstract: We previously demonstrated that embryonic stem (ES) cell self-renewal required sustained signaling by leukemia inhibitory factor (LIF) in a concentration-dependent manner, allowing us to hypothesize that thresholds in ligand-receptor signaling modulate stem cell differentiation control. To test this hypothesis, we have experimentally and computationally compared the abilities of two gp130-signaling cytokines (LIF and Hyper-interleukin-6 [HIL-6]) to sustain ES cell self-renewal. Quantitative measurements of ES cell phenotypic markers (stage-specific embryonic antigen-1 and E-cadherin), functional assays (alkaline phosphatase activity and embryoid body formation efficiency), and transcription factor (Oct-4) expression over a range of LIF and HIL-6 concentrations demonstrated a superior ability of LIF to maintain ES cell pluripotentiality at higher concentrations (> or =500 pM). Additionally, we observed distinct qualitative differences in the ES cell self-renewal dose response profiles between the two cytokines. A computational model permitted calculation of the number of signaling complexes as a function of receptor expression, ligand concentration, and ligand/receptor-binding properties, generating predictions for the degree of self-renewal as a function of cytokine concentration by comparison of these calculated complex numbers to experimentally determined threshold cytokine concentrations. Model predictions, consistent with experimental data, indicated that differences in the potencies of these two cytokines were based primarily on differences in receptor-binding stoichiometries and properties. These results support a ligand/receptor signaling threshold model of ES cell fate modulation through appropriate types and levels of cytokine stimulation. Insights from these results may be more generally applicable to tissue-specific stem cells and could aid in the development of stem cell-based technologies.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, Roseburgh Building, University of Toronto, 4 Taddle Creek Road, Toronto, Ontario, M5S 3G9, Canada.
authors.forename: Sowmya
authors.initials: S
authors.lastname: Viswanathan
authors.forename: Tania
authors.initials: T
authors.lastname: Benatar
authors.forename: Stefan
authors.initials: S
authors.lastname: Rose-John
authors.forename: Doug A
authors.initials: DA
authors.lastname: Lauffenburger
authors.forename: Peter W
authors.initials: PW
authors.lastname: Zandstra
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D019070:Cell Lineage / Q000187:drug effects / Q000502:physiology*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D050822:Cytokine Receptor gp130; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism*; D006131:Growth Inhibitors / Q000378:metabolism* / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology; D053605:Leukemia Inhibitory Factor; D008024:Ligands; D008222:Lymphokines / Q000378:metabolism* / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D015233:Models, Statistical; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D006131:Growth Inhibitors; C494200:Il6st protein, mouse; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D008024:Ligands; D008222:Lymphokines; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D050822:Cytokine Receptor gp130