Control parameters of primary waves (bifurcations) in somitogenesis

Determine the cellular and molecular control parameters that govern the primary waves (i.e., the bifurcations) in vertebrate somitogenesis, including whether these parameters are set by external morphogen gradients (such as FGF or Wnt), local intrinsic cues within presomitic mesoderm cells, or cell-to-cell interactions, and elucidate how these control parameters coordinate the sequence of clock-stopping and anterior–posterior polarity bifurcations.

Background

Throughout the review, the authors characterize ‘primary waves’ as moving boundaries in space–time where dynamical-system bifurcations occur (e.g., clock arrest via Hopf or SNIC and emergence of anterior–posterior bistability). While models and experiments suggest candidate mechanisms, the specific control parameters that trigger and coordinate these bifurcations remain unresolved.

Clarifying which signals (e.g., morphogen gradients), intrinsic cellular states (e.g., oscillator phase differences, timers), or intercellular couplings act as control parameters—and how they couple or feed back—would unify multiple segmentation phenomena, including period slowing, wavefront positioning, and AP fate stabilization.