Synchrony Dynamics During Initiation, Failure, and Rescue of the Segmentation Clock

TLDR

The segmentation clock coordinates sequential body‑axis segmentation in vertebrate embryos through a multicellular genetic network of synchronized oscillators coupled by Delta‑Notch signaling, yet the mechanisms establishing synchrony and its loss in mutants remain unknown. This study aims to develop a physical theory of the segmentation clock’s synchrony dynamics to explain defect onset, rescue, robustness, and a critical point beyond which synchrony decays. The authors varied Notch coupling strength and timing in zebrafish embryos using quantitative perturbation techniques and built a coupled phase‑oscillator model to capture the observed synchrony dynamics. They found that synchrony arises through simultaneous initiation and self‑organization, and that the position of segmentation defects is determined by the difference between coupling strength and developmental noise.

Abstract

The “segmentation clock” is thought to coordinate sequential segmentation of the body axis in vertebrate embryos. This clock comprises a multicellular genetic network of synchronized oscillators, coupled by intercellular Delta-Notch signaling. How this synchrony is established and how its loss determines the position of segmentation defects in Delta and Notch mutants are unknown. We analyzed the clock's synchrony dynamics by varying strength and timing of Notch coupling in zebra-fish embryos with techniques for quantitative perturbation of gene function. We developed a physical theory based on coupled phase oscillators explaining the observed onset and rescue of segmentation defects, the clock's robustness against developmental noise, and a critical point beyond which synchrony decays. We conclude that synchrony among these genetic oscillators can be established by simultaneous initiation and self-organization and that the segmentation defect position is determined by the difference between coupling strength and noise.