RNA-Protein Dynamics of the Segmentation Clock and Its Implications in Developmental Disorders

Somitogenesis is orchestrated by the segmentation clock, a highly conserved developmental oscillator that generates periodic gene expression waves to establish precise somite boundaries along the vertebrate body axis. While transcriptional feedback circuits and signaling gradients are recognized as central determinants of clock dynamics, accumulating evidence indicates that RNA-centered regulation provides an important layer of temporal control. We therefore focus primarily on established RNA-regulatory processes, including nascent RNA synthesis, pre-mRNA processing, transcript stability and degradation, and translational control, and examine how these processes interact with protein turnover and intercellular signaling to shape oscillation period, amplitude, and synchronization. Because the molecular implementation of the clock differs among vertebrates, we distinguish species-specific systems throughout: mouse studies primarily define hairy and enhancer of split 1 (Hes) 7/lunatic fringe (Lfng)/Delta-like canonical Notch ligand (Dll) 1 dynamics, zebrafish studies define Hes-related bHLH transcriptional repressor (her) 1/her7/deltaC/deltaD dynamics, chick studies established cyclic c-hairy1/lfng expression, and human HES7/LFNG dynamics are examined mainly in stem-cell-derived presomitic mesoderm (PSM) models. These mechanisms are used to formulate experimentally testable hypotheses about phase-dependent RNA stability, translation, and developmental state transitions. Together, the segmentation clock provides a quantitative framework for distinguishing established RNA-protein mechanisms from emerging RNA-regulatory hypotheses and for understanding how their disruption may contribute to congenital vertebral disorders.