We believe that Cx43 is the major GJ in H-GJC between microglia and F98 cells in our study because: (1) Cx43 is the predominant GJs on F98 cells, whereas the expression of Cx32, Cx36 and Cx45 in F98 glioma cells were negative (data not shown), (2) only homotypical GJCs are functional [22], and (3) the trans-junctional current amplitudes, conductance and activation pattern give rise to Cx43-based properties. This evidence concerns the gene GJA1 and central nervous system cancer.