Neural progenitor cells (NPCs) are sensitive to epidermal growth factor (EGF), which is essential for their self-renewal. Recently we showed that high level of connexin43 (Cx43) expression and gap junctional intercellular communication (GJIC) are also required to maintain NPCs in a proliferative state. In this study the connection between EGF/EGFR signalling and Cx43 expression was investigated during proliferation and differentiation of cultured ReNcell VM197 human NPCs. We found that EGF, but not basic fibroblast growth factor (bFGF), strongly stimulated both Cx43 expression and GJIC in proliferating cells. This stimulatory effect was blocked by AG1478, a specific inhibitor for EGFR kinase. Notably, knockdown of Cx43 strongly inhibited the cell proliferation promoted by EGF/EGFR signalling. High sensitivity to EGF was still maintained in differentiated NPCs. Administration of EGF to differentiating cells led to a pronounced increase (9-fold) of Cx43 expression and a re-induction of proliferation. This strong impact of EGF was found to correlate with a surprisingly massive 60-fold up-regulation of EGFR expression in differentiated cells. Our data argue for a mutual regulation between Cx43 expression and EGF/EGFR signalling during self-renewal and differentiation of NPCs.
Keywords: 5-ethynyl-2′-deoxyuridine; Connexin; Cx(s); Differentiation; EGF; EGF/EGFR signalling; EGFR; EdU; FRAP; GFAP; GJ(s); GJIC; Gap junctions; Growth factor; Human neural progenitors; NPC(s); bFGF; basic fibroblast growth factor; connexin(s); epidermal growth factor; epidermal growth factor receptor; fluorescence recovery after photobleaching; gap junction(s); gap junctional intercellular communication; glial fibrillary acidic protein; neural progenitor cell(s); siRNA; small interfering RNA.