Small rho gtpases in mammalian somitogenesis

Presomitic Mesoderm (PSM) is an embryonic tissue primarily organised along the main anterior-posterior(A/P) axis of vertebrates and periodically forms somites at its anterior end. Somitogenesis depends on gene transcription waves sweeping through the PSM from its posterior to the anterior end with a characteristic periodicity called the segmentation clock. In a 2D in vitro PSM model, we applied chemical perturbations on signaling pathways associated with cell motility, directionality, polarity and mechanosensitivity. We found that Rac1 small GTPase inhibitors can broadly modify the periodicity of the gene transcription waves, resulting in unique phenotypic shifts of the somitic patterning. By investigating the causes of these spatiotemporal changes, we revealed that Rac1 small GTPase inhibitors modified the transcriptome in the PSM tissue and more specifically the expression profile of PSM marker genes like Wnt and Notch targets.