Emergent dynamics of cellular decision making in multi-node mutually repressive regulatory networks

Stem cell differentiation during development is governed by the dynamics of the underlying gene regulatory networks (GRNs). Mutually inhibiting nodes/collection of nodes encompass the GRNs that govern differentiation to two distinct fates. However, the properties of GRNs that can allow differentiation into n-terminal phenotypes are poorly understood. In this study, we examine toggle-n networks, encompassing mutual inhibitions among multiple transcription factors (TFs), to derive generalized insights regarding the dynamics underlying differentiation into n-terminal phenotypes. We show through numerical and analytical methods that steady-state distributions of these networks involve co-expression of multiple cell state-specific TFs, indicating the presence of multi-potent hybrid phenotypes during multi-lineage differentiation. Furthermore, incorporating a case study of T-helper cell differentiation, we show that cytokine signalling and specific asymmetry of regulatory links can drive further directed differentiation of these hybrid phenotypes into particular cell states within our mathematical framework.