To study the contribution of CD133 to proneural GBM subgroup formation and elucidate the intertwined relation between CD133+ neural stem cells and vasculature in vivo, we used a mouse model in which the reporter gene LacZ was introduced in the Prom1 locus under control of Prom1 promoter [12], thus avoiding the limitations created by deficient recognition of a functional group on CD133 protein. The gene discussed is PROM1; the disease is glioblastoma.