Fig. 6.

Dominant-negative Akt induced apoptosis in primary cultures of immature oligodendrocytes. Adenoviruses encoding wild-type Akt or a dominant-negative Akt were used to express recombinant proteins in primary cultures of immature oligodendrocytes. Adenovirus infection was performed on oligodendrocyte precursors 24 hr after incubation in PDGF/T3. A, Cells were subjected to O4 staining and TUNEL analysis 72 hr after infection. The wild-type Akt infection did not induce apoptosis (bottom panel), but dominant-negative Akt infection did induce apoptosis (top and middle panels). B, Expression of wild-type Akt and dominant-negative Akt was assessed by immunoblot with anti-HA antibody; 50 MOI for wild-type Akt and 10 MOI for dominant-negative Akt showed similar levels of Akt expression. Thus, 50 MOI of wild-type Akt and 10 MOI of dominant-negative Akt were used for TUNEL experiments in A. Lysate of cells infected with adenovirus encoding green fluorescent protein was used for control (C). C, O4-positive cells were examined randomly in 20 different fields. In total, 241 cells were examined for dominant-negative Akt virus infection and 171 cells for wild-type Akt virus infection. TUNEL positivity is shown as a percentage of the total number of O4-positive cells. Dominant-negative Akt infection caused apoptosis in O4-positive oligodendrocytes at a significantly higher rate compared to wild-type Akt infection (*p < 0.001).