Cell polarity is defined by the establishment of segregated signaling domains in the plasma membrane and cytoplasm, and it is essential for a range of cell functions, including motility, barrier formation, and fate determination. Initially, uniform cells polarize through symmetry breaking, triggered spontaneously or under the guidance of internal/external cues. A recurring motif to establish polarity across a variety of cell systems is the use of local positive feedback loops, whereas maintenance of polarity often involves mutual antagonism between diametric signaling modules, evident in the front-rear of a migrating cell or the anterior-posterior of the C. elegans zygote. Polarity networks are composed of diverse signaling effectors, including but not limited to mechanical forces, active transport, cell-cell contact and kinases/phosphatases. During development, cells can convert between different forms of polarity, as exemplified by epithelial to mesenchymal transitions, whereas inappropriate lost or conversion of polarity is thought to be a driver of disease. Thus, delineating the regulatory logic of polarity networks has the potential to improve human health.
Although substantial advances have been made in identifying individual components of polarity networks, there are still many exciting avenues to explore. An astonishing number of cues can influence polarity, including electric fields, shear stress, and environmental rigidity, but it remains unclear how cells integrate and prioritize different cues. Once cues have been perceived, the resulting mechanical and chemical signaling pathways must crosstalk, but it is poorly understood how they do so. Polarity networks are also complex and redundant, making it difficult to identify core components.
Recent experimental advances have begun to address this complexity. Polarity has been recapitulated in apolar cells, providing fundamental insights into polarity network design. Advances in optogenetics now allow the manipulation of protein activity and localization on the seconds to minutes time scale, indicating that directly, locally activating downstream components can self-organize polarity. Sophisticated microfluidic devices are able to provide multiple cues in well controlled environments and allow high resolution imaging of cellular outcomes. These and many other advances are thus poised to move the field forward.
Following the success of the first volume
/Establishing and Maintaining Cell Polarity, In this Research Topic, we welcome Original Research, Methods, Reviews, and Opinion articles which highlight advances in the cell polarity field along, but not limited to, the following subtopics:
• How cell polarity networks integrate multiple cues
• Context dependent hierarchy between cues
• Maintenance of cell polarity in the face of biological noise
• Minimal signaling modules to induce polarity in apolar cells
• Techniques to present multiple cues to cells in a precise manner
• New techniques to induce or redirect cell polarity
• Intersections between chemical and mechanical signaling pathways
