Somitogenesis (Segmentation Clock)
Oscillating gene expression driving periodic formation of somites.
Overview
Somitogenesis is the process of forming somites — blocks of mesoderm that give rise to vertebrae, ribs, skeletal muscle, and dermis. A molecular oscillator ('segmentation clock') in the presomitic mesoderm involves cyclic expression of genes in the Notch, Wnt, and FGF pathways. The clock period (varies by species: ~30 min in zebrafish, ~2 h in mouse, ~5 h in human) determines when cells reach the wavefront (defined by opposing FGF/Wnt and RA gradients) and segment.
Cellular Location
Presomitic mesoderm → somites
Clinical Significance
Defects cause spondylocostal dysostosis and congenital vertebral malformations; in vitro somitogenesis from PSCs recapitulates this process; reveals fundamental principles of biological timing.
Key Molecules
Key Enzymes
Related Pathways
Notch Signaling Pathway
Juxtacrine signaling controlling cell fate decisions via proteolytic receptor activation.
Wnt/β-Catenin Pathway
Controls cell fate, proliferation, and polarity through β-catenin stabilization.
FGF Signaling
Fibroblast growth factor signaling controlling proliferation, differentiation, and organogenesis.
Retinoic Acid Signaling
Vitamin A-derived morphogen controlling anterior-posterior patterning.