UC Berkeley

EphB4 receptor tyrosine kinases bind and cluster with membrane bound ephrinB2 ligands on apposing cells to signal juxtacrine. While this signal activation plays a regulatory role in neural stem cell differentiation, the underlying biophysical mechanism remains poorly understood. We reconstituted this juxtacrine signalling geometry between live EphB4-expressing neural stem cells and a supported lipid bilayer presenting laterally mobile monomeric ephrinB2 ligands. A novel method was developed to study neural stem cell differentiation by this hybrid system. This setup allows for observations of the timescale and spatial distribution of receptor-ligand binding and clustering. Furthermore, it accommodates the method of spatial mutation—whereby physical constraints are imposed by lithographically patterned micro-corrals—to restrict EphB4 receptor mobility and precisely control the spatial patterns of receptor-ligand organisation. We found that this physical reorganisation of EphB4-ephrinB2 inhibits neuronal differentiation, suggesting spatial and mechanical sensing of EphB4 signalling in neural stem cells.