biological replicates; Figure 6B), the difference fell short of significance. Therefore, we examined the effect of NHE9 knockdown in primary cultured human glioma cells (Figure 6C). We did observe significant acidification of endosomes upon NHE9 knockdown (pH 6.60, p<0.05; Student's t-test, n= three biological replicates) relative to control (pH 6.88). These results suggest functional differences between mouse and human astrocyte cells, consistent with the limitations of the mouse model in recapitulating human disease. It is possible that NHE6 compensates for loss of NHE9 in mouse cortical astrocytes. Indeed, we observed high levels of co-localization of NHE6-GFP and NHE9-DsRed in murine astrocytes (Figure 5E–F), consistent with redundant roles for NHE6 and NHE9 in regulating endosomal pH.
