Dynamics and function of CXCR4 in formation of the granule cell layer during hippocampal development

In the developing hippocampus, granule cell progenitors (GCPs) arising in the ventricular zone (VZ) migrate to the subpial region, and form the granule cell layer (GCL) of the dentate gyrus (DG). To understand the mechanism of GCL formation, we investigated the dynamics and function of CXCR4 which is expressed by the GCPs and is a receptor of the CXCL12 chemokine secreted by cells surrounding the DG. In the VZ, CXCR4 was expressed on the plasma membrane of the GCPs. During their migration and in the DG, CXCR4 was internalized and accumulated as puncta close to the centrosomes, Golgi apparatus, and lysosomes. Phosphatase analysis suggested that both phosphorylated and dephosphorylated CXCR4 exist on the plasma membrane, whereas CXCR4 in intracellular puncta was mainly dephosphorylated. Intraventricular administration of the CXCR4 antagonist AMD3100 resulted in the disappearance of CXCR4 expression from the intracellular puncta, and its appearance on the plasma membranes. Furthermore, AMD3100 treatment resulted in precocious differentiation, delayed migration, and ectopic GCPs. Taken together, these results suggest that during the development and migration of GCPs, CXCR4 on the plasma membrane is phosphorylated, internalized, sorted to the centrosomes, Golgi apparatus, and lysosomes, and functionally regulates GCP differentiation, migration and positioning.