Mechanosensitive stem cell fate choice is instructed by dynamic fluctuations in activation of Rho GTPases

• Published in: Proceedings of the National Academy of Sciences - PNAS 2023-05, Vol.120 (22), p.e2219854120-e2219854120
• Main Authors: Sampayo, Rocío G, Sakamoto, Mason, Wang, Madeline, Kumar, Sanjay, Schaffer, David V
• Format: Article
• Language: English
• Subjects: cdc42 GTP-Binding Protein - metabolism; Cdc42 protein; Cell Differentiation; Cell fate; Differentiation; Embryo cells; Extracellular matrix; Genetics; Guanosine triphosphatases; Information processing; Mechanical stimuli; Neural stem cells; Neural Stem Cells - metabolism; Neurogenesis; Optics; Phosphorylation; rho GTP-Binding Proteins - genetics; rho GTP-Binding Proteins - metabolism; rhoA GTP-Binding Protein - metabolism; RhoA protein; Signal Transduction; Stem cells; Stiffness
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2219854120

During the intricate process by which cells give rise to tissues, embryonic and adult stem cells are exposed to diverse mechanical signals from the extracellular matrix (ECM) that influence their fate. Cells can sense these cues in part through dynamic generation of protrusions, modulated and controlled by cyclic activation of Rho GTPases. However, it remains unclear how extracellular mechanical signals regulate Rho GTPase activation dynamics and how such rapid, transient activation dynamics are integrated to yield long-term, irreversible cell fate decisions. Here, we report that ECM stiffness cues alter not only the magnitude but also the temporal frequency of RhoA and Cdc42 activation in adult neural stem cells (NSCs). Using optogenetics to control the frequency of RhoA and Cdc42 activation, we further demonstrate that these dynamics are functionally significant, where high- vs. low-frequency activation of RhoA and Cdc42 drives astrocytic vs. neuronal differentiation, respectively. In addition, high-frequency Rho GTPase activation induces sustained phosphorylation of the TGFβ pathway effector SMAD1, which in turn drives the astrocytic differentiation. By contrast, under low-frequency Rho GTPase stimulation, cells fail to accumulate SMAD1 phosphorylation and instead undergo neurogenesis. Our findings reveal the temporal patterning of Rho GTPase signaling and the resulting accumulation of an SMAD1 signal as a critical mechanism through which ECM stiffness cues regulate NSC fate.