They found that the reduction in AQP4ex, leading to reduction and delocalization of AQP4, could be likely to undermine the integrity of the BBB, indicating that AQP4ex could be considered as a potential new early biomarker of GBM progression and a target for AQP4 modulation (Frigeri et al., 2007). The gene discussed is AQP4; the disease is glioblastoma.