Two distinct timers control vertebrate embryo segmentation

Vertebrate embryos form repeated body-axis segments, yet the segmentation-clock period does not always match the timing of somite formation. Real-time clock imaging combined with pharmacological and surgical perturbations identifies two timers: a clock that establishes an initial commitment and a subsequent self-organizing hourglass process. Hourglass duration scales with somite size and depends on cytoskeletal regulation. Changing this timer can turn regular zebrafish segmentation into irregular patterns resembling the anterior chicken embryo and alter the number of predetermined compartments and somite sizes. The findings separate commitment from segmentation as interacting modules.

QLS–CAMBAM hybrid seminar with Ertuğrul M. Özbudak (Northwestern University), 2026-10-20, 12:00–13:00 Montréal time. Attend in person at 550 Sherbrooke, Room 189, McGill University, or follow the public Zoom link on the official event page. Open to the university community, including faculty, graduate and undergraduate students.