NG2 cell-specific inactivation of Vhl results in polycythemia. (A) Mice with NG2 cell-specific inactivation of Vhl develop red paws, ears, and snout, splenomegaly, and polycythemia (n = 3-7). (B) Inactivation of Vhl in NG2 cells induces erythropoiesis and increases plasma EPO. Shown are individual Hct, RBC, and Hb values for Cre⁻ control (n = 22), NG2-Vhl^+/− (n = 6), and NG2-Vhl^−/− mice (n = 16). Bar graphs show serum EPO levels (sEPO) for Cre⁻ control (n = 20), NG2-Vhl^+/− (n = 6), and NG2-Vhl^−/− (n = 11) mice. Data are represented as mean ± SEM; 1-way ANOVA followed by Tukey’s post hoc analysis; ***P < .001 compared with control group. (C) Relative Epo mRNA levels in retina, spleen, brain, kidney, bone, muscle, skin, liver, and heart in Cre⁻ control and NG2-Vhl^−/− mice (n = 3-7). (Inset) Brain and kidney EPO protein levels in Cre⁻ control and NG2-Vhl^−/− mice expressed as pg/mg total tissue protein (n = 5-7). Data are represented as mean ± SEM; 2-tailed Student t test; *P < .05, **P < .01, and ***P < .001 compared with Cre⁻ controls. (D) Epo mRNA levels in striatal (ST), hypothalamic (HYT), cortical (CTX), and hippocampal (HP) subregions from Cre⁻ (n = 12), NG2-Vhl^+/− (n = 3), and NG2-Vhl^−/− mice (n = 4). Data are represented as mean ± SEM; 1-way ANOVA followed by Tukey’s post hoc analysis; ***P < .001 compared with the Cre⁻ control group. BW, total body weight; W, organ weight.