Cell-cell communication through FGF4 generates and maintains robust proportions of differentiated cell types in embryonic stem cells

Abstract

During embryonic development and tissue homeostasis, reproducible proportions of differentiated cell types are specified from populations of multipotent precursor cells. Molecular mechanisms that enable both robust cell type proportioning despite variable initial conditions in the precursor cells, as well as the re-establishment of these proportions upon perturbations in a developing tissue remain to be characterised. Here we report that the differentiation of robust proportions of epiblast-like and primitive endoderm-like cells in mouse embryonic stem cell cultures emerges at the population level through cell-cell communication via a short-range FGF4 signal. We characterise the molecular and dynamical properties of the communication mechanism, and show how it controls both robust cell type proportioning from a wide range of experimentally controlled initial conditions, as well as the autonomous re-establishment of these proportions following the isolation of one cell type. The generation and maintenance of reproducible proportions of discrete cell types is a new function for FGF signalling that may operate in a range of developing tissues.

Intermittent ERK oscillations downstream of FGF in mouse embryonic stem cells

“…These concentrations cover the dynamic range of FGF4-response at the level of ERK phosphorylation and transcription of an FGF/ERK-dependent reporter gene ( ), as well as differentiation along the primitive endoderm lineage ( Raina et al, 2021 ). To measure the steady-state signaling response to different ligand levels, we pre-treated cells with the respective FGF4 concentrations for 24 h in N2B27 supplemented with Chiron and LIF to maintain pluripotency.…”

“…Negative feedback in the RAF-MEK-ERK cascade sets a ligand dose response range, and linearizes signal transduction despite non-linear signal amplification ( Sturm et al, 2010 ). In ESCs and cells of the early embryo, FGF4 concentration smoothly tunes the proportion of differentiated cell types ( Krawchuk et al, 2013 ; Raina et al, 2021 ). Thus, ERK oscillations in ESCs might be the consequence of negative feedback mechanisms that have evolved to tune the response range of the signal transduction system to the physiologically relevant range of paracrine FGF4 concentration.…”

“…The differentiation of extra-embryonic primitive endoderm cells in the mouse preimplantation embryo depends on FGF/ERK signaling in a dose-dependent manner ( Kang et al, 2013 ; Krawchuk et al, 2013 ). Embryonic stem cells (ESCs), clonal cell populations that retain the differentiation potential of inner cell mass cells of the preimplantation embryo, are a tractable model system that recapitulates this dose-dependent function of FGF4 ( Raina et al, 2021 ; Schröter et al, 2015 ). FGF/ERK signaling is also required for maturation of the epiblast lineage in the embryo ( Kang et al, 2017 ; Ohnishi et al, 2014 ), and controls the corresponding process of transitioning from naïve to primed pluripotency and lineage commitment in ESCs ( Kunath et al, 2007 ; Molotkov et al, 2017 ).…”

Initial source of heterogeneity in a model for cell fate decision in the early mammalian embryo

“…The noise necessary to initiate cell specification has been often modelled by considering variability in the initial conditions [11,[31][32][33], although asynchronous cell division times and distribution of the concentrations at division have also been considered [11,20,33]. This source of noise was shown to be able to reproduce the appropriate specification mechanism, a spatial configuration in which different cell types are intermingled, as well as robust proportions of differentiated cell types.…”

“…Therefore, in the model, the level of noise must be chosen with precaution to reproduce experimental observations. To this end, it seems relevant, as a perspective, to perform a similar statistical comparison based on a mesoscopic approach where the noise is not included arbitrarily to a selected parameter/variable at the beginning of the simulations but is intrinsic to the method and is present during the whole evolution of the system [32][33][34].…”