Differential expression of CXCL12 and CXCR4 during human fetal neural progenitor cell differentiation

Stromal cell-derived factor 1 alpha (SDF-1alpha, CXCL12) and its receptor CXCR4 play an important role in the central nervous system (CNS) development and adulthood by mediating cell migration, enhancing precursor cell proliferation, assisting in neuronal circuit formation, and possibly regulating migration during repair. The expression pattern of CXCR4 and CXCL12 during neurogenesis has not been thoroughly elucidated. In this study, we investigated the expression of CXCL12 and CXCR4 during neural progenitor cells (NPC) differentiation by microarray analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) using human fetal NPC as a model system. The production of CXCL12 was measured by enzyme-linked immunosorbent assay (ELISA). CXCR4 expression was determined by florescence-activated cell sorting (FACS) analysis, immunocytochemical staining, and CXCR4-mediated inhibition of cyclic AMP (cAMP) accumulation. Our data demonstrated that CXCR4 expression is significantly upregulated when NPC are differentiated into neuronal precursors, whereas CXCL12 is upregulated when differentiated into astrocytes. We also provide evidence that CXCR4 localization changes as neurons mature. In neuronal precursors, CXCR4 is localized in both neuronal processes and the cell body, whereas in mature neurons, it is primarily expressed on axons and dendrites. This differential expression of CXCR4 and CXCL12 may be important for the temporal regulation of neuronal migration and circuit formation during development and possibly in adult neurogenesis and repair.