The hematopoietic stem cell polarization and migration: A dynamic link between RhoA signaling pathway, microtubule network and ganglioside-based membrane microdomains.

The polarization and migration of eukaryotic cells are fundamental processes for the development and maintenance of a tissue. These aspects gain especial interest when it comes to stem and progenitor cells in the way that their manipulation might open new avenues in regenerative therapy. In recent years, novel biological facets of migrating hematopoietic stem cells were revealed by several groups, including ours. Among these features, the polarization of their membranous (proteins and lipids) and cytoplasmic constituents, which leads to the formation of a specialized sub-cellular structure located at the rear pole-the uropod-has gained increasing interest. In a new study we have demonstrated that such phenomena involve a coordinated mechanism between Rho GTPase signaling and the microtubule network. Specifically, our results based on the use of synthetic inhibitors and RNA interference suggest that the activity of RhoA and its effector ROCK I is indispensable for cell polarization and the active reorganization of microtubules that are required for migration.