Fine-tuning ERK activity enables proliferation-differentiation balance during lineage specification of human embryonic stem cells

It is well documented that differentiation of stem cells is generally associated with and facilitated by an elongated cell cycle. However, for lineage specification requiring high ERK activity, which also promotes proliferation, it is unclear how stem cells simultaneously negotiate the “proliferation-differentiation” decision. Here we investigate this question using multiplex quantitative live-cell imaging to track embryonic stem cells (ESC) differentiation into mesendoderm (ME) lineage with high ERK activity. We show that ERK activity increase manifested by a heightened ERK oscillation frequency drove robust ME differentiation accompanied by a modest cell cycle acceleration. We profile the responses of ME differentiation and cell cycle length as a function of a synthetic ERK oscillatory activity gradient. Our results reveal that these two processes took place in distinct ranges of ERK oscillation frequency, with ME differentiation requiring higher level for ERK oscillation to secure efficient ME protein translation. Interactions between gastrulation morphogens recapitulated an ERK oscillation gradient, potentiating heterogeneous ME fates while maintaining a comparable level of proliferation. Our study thus provides mechanistic insights into how ERK fine-tunes proliferation and differentiation during cell fate specification