title: A model-based analysis of culture-dependent phenotypes of mESCs.
abstract: Mouse embryonic stem cells (mESCs) can be maintained in a proliferative and undifferentiated state over many passages (self-renewal) while retaining the potential to give rise to every cell type of the organism (pluripotency). Autocrine FGF4/Erk signalling has been identified as a major stimulus for fate decisions and lineage commitment in these cells. Recent findings on serum-free culture conditions with specific inhibitors (known as 2i) demonstrate that the inhibition of this pathway reduces transcription factor heterogeneity and is vital to maintain ground state pluripotency of mESCs. We suggest a novel mathematical model to explicitly integrate FGF4/Erk signalling into an interaction network of key pluripotency factors (namely Oct4, Sox2, Nanog and Rex1). The envisaged model allows to explore whether and how proposed mechanisms and feedback regulations can account for different expression patterns in mESC cultures. We demonstrate that an FGF4/Erk-mediated negative feedback is sufficient to induce molecular heterogeneity with respect to Nanog and Rex1 expression and thus critically regulates the propensity for differentiation and the loss of pluripotency. Furthermore, we compare simulation results on the transcription factor dynamics in different self-renewing states and during differentiation with experimental data on a Rex1GFPd2 reporter cell line using flow cytometry and qRT-PCR measurements. Concluding from our results we argue that interaction between FGF4/Erk signalling and Nanog expression qualifies as a key mechanism to manipulate mESC pluripotency. In particular, we infer that ground state pluripotency under 2i is achieved by shifting stable expression pattern of Nanog from a bistable into a monostable regulation impeding stochastic state transitions. Furthermore, we derive testable predictions on altering the degree of Nanog heterogeneity and on the frequency of state transitions in LIF/serum conditions to challenge our model assumptions.
authors.affiliation: Institute for Medical Informatics and Biometry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Herberg
authors.affiliation: Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Tüzer
authors.initials: T
authors.lastname: Kalkan
authors.affiliation: Institute for Medical Informatics and Biometry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Glauche
authors.affiliation: Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Austin
authors.initials: A
authors.lastname: Smith
authors.affiliation: Institute for Medical Informatics and Biometry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Roeder
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D003198:Computer Simulation; D016895:Culture Media, Serum-Free; D053595:Embryonic Stem Cells / Q000502:physiology*; D018398:Homeodomain Proteins / Q000378:metabolism; D053605:Leukemia Inhibitory Factor / Q000502:physiology; D051379:Mice; D008954:Models, Biological; D000071317:Nanog Homeobox Protein; D010641:Phenotype; D055550:Protein Stability; D015398:Signal Transduction
chemical_list: D016895:Culture Media, Serum-Free; D018398:Homeodomain Proteins; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D000071317:Nanog Homeobox Protein; C475540:Nanog protein, mouse