Substrate Rigidity Modulates Segmentation Clock Dynamics in Isolated Presomitic Mesoderm Cells.

The segmentation clock, a genetic oscillator in the presomitic mesoderm (PSM), is known to be influenced by biochemical signals, yet its potential regulation by mechanical cues remains unclear. The complex PSM microenvironment has made it challenging to isolate the effects of mechanical perturbations on clock behavior. Here we investigated how mechanical stimuli affect clock oscillations by culturing zebrafish PSM cells on PDMS micropost arrays with tunable rigidities (0.6-1200 kPa). We observed an inverse sigmoidal relationship between surface rigidity and both the percentage of oscillating cells and the number of oscillation cycles, with a switching threshold between 3-6 kPa. The periods of oscillating cells showed a consistently broad distribution across rigidity changes. Moreover, these cells exhibited distinct biophysical properties, such as reduced motility, contractility, and sustained circularity. These findings highlight the crucial role of cell-substrate interactions in regulating segmentation clock behavior, providing insights into the mechanobiology of somitogenesis. The oscillatory behaviors of single PSM cells respond to substrate rigidity in a switch-like manner, with a critical threshold between 2.9 kPa and 6 kPa.As rigidity increases, both the oscillation percentage and the number of cycles decrease, while the period does not show a clear dependency on rigidity.Oscillating cells exhibit distinct biophysical properties compared to non-oscillating cells, including higher and more sustained circularity, lower motility, and reduced contractility.Cell aggregates exhibit similar trends in response to rigidity, except for significantly increased oscillation percentages across different rigidity conditions, suggesting a potential interplay between cell-cell communications and rigidity in influencing cell aggregate behavior.