This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A molecular pathway known for controlling cell shape and movement also helps regulate the rhythm by which the vertebrate body is divided into repeated segments, FMI researchers report in the journal Development. The work links cell behavior to the segmentation clock that guides the formation of vertebrae and other tissues, and may help explain developmental conditions involving congenital spinal malformations.
During early development, waves of gene activity sweep through the presomitic mesoderm, a temporary strip of embryonic tissue that is progressively divided into somites—paired blocks of cells that later form vertebrae, skeletal muscle and part of the skin. Each wave helps trigger the formation of a new pair of somites. In mice, a new pair of somites forms roughly every two hours, paced by an internal molecular clock called the segmentation clock.
After screening a collection of compounds that perturb cell mechanics and signaling, Charisios Tsiairis and Maria Pappa, his former Ph.D. student, identified Rac1 as an unexpected regulator of the segmentation clock. Rac1 is a signaling protein usually linked to cell shape, movement and the cytoskeleton. Using cultured mouse embryonic tissue, the team found that disrupting Rac1 signaling slowed the segmentation clock without preventing cells from remaining synchronized.
The perturbation also changed the developmental output of the clock. Treated tissue formed fewer somites, but each somite was longer, while the overall length of the tissue remained similar. The researchers also detected changes in selected genes controlled by the Notch and Wnt pathways, which are central components of the segmentation system.
"The findings suggest that developmental timing is closely connected to the pathways that control how cells move, change shape and interact with their surroundings," Tsiairis says. "They highlight an unexpected link between cell mechanics and the molecular clock that patterns the vertebrate body." The work may also help researchers understand developmental disorders that affect the spine, he adds. Defects in somite formation can contribute to congenital vertebral malformations, including abnormalities associated with the VACTERL spectrum, a group of conditions affecting several organs.
"Understanding how cell behavior influences the segmentation clock could provide insight into the mechanisms underlying some of these conditions." Maria Pappa et al, Perturbation of Rac1 signaling alters segmentation clock dynamics and somite size, Development (2026). DOI: 10.1242/dev.205231 Provided by Friedrich Miescher Institute for Biomedical Research BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.
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