Abstract
During embryonic development and tissue homeostasis, reproducible proportions of differentiated cell types need to be specified from homogeneous precursor cell populations. How this is achieved despite uncertainty in initial conditions in the precursor cells, and how proportions are re-established upon perturbations in the developing tissue is not known. Here we report the differentiation of robust proportions of epiblast- and primitive endoderm-like cells from a wide range of experimentally controlled initial conditions in mouse embryonic stem cells. We demonstrate both experimentally and theoretically that recursive cell-cell communication via FGF4 establishes a population-based mechanism that generates and maintains robust proportions of differentiated cell types. Furthermore, we show that cell-cell communication re-establishes heterogeneous cell identities following the isolation of one cell type. The generation and maintenance of robust cell fate proportions is a new function for FGF signaling that may extend to other cell fate decisions.