GADD45B and Parkinson disease: In the diseased striatum, compared to GADD45β+/+ mice, mice lacking GADD45β had significantly increased expression of ΔFosB (a transcription factor that is a critical mediator in maladaptive neuroplasticity in PD) and c-Fos (immediate early gene, a mark of acute neuronal activity) (162, 163) (Figure 3).