Fig.2.

Forced neuronal cell cycle re-entry induces microglia activation. A) Immunofluorescence labeling shows SV40T and NeuN co-label (arrows) in 4-month-old NCCR mice (n = 4). TAg control animals (n = 4) do not show SV40T immunofluorescence. B) Immunofluorescence labeling shows PCNA and NeuN co-label (arrows) in 4-month-old NCCR mice (n = 4). TAg control animals (n = 4) do not show PCNA immunofluorescence. C, a) NCCR animals (n = 3) maintained on standard (Std) diet starting at 1 month of age and examined at 3 months of age show persistent expression of SV40T and PCNA (marker of cell cycle activation) in the cortex (shown) and hippocampus (data not shown). C, b) The SV40T expression is tightly regulated by dox diet in the NCCR mice. SV40T and PCNA stains are absent in a separate group of NCCR mice (n = 3) that are put back on dox diet at 2 months of age and examined at 3 months of age. C, c) The NCCR animals that are continuously maintained on dox diet (n = 3) do not show any SV40T or PCNA stains. D, a) The same animals in Ca show Iba-1 labeled rod-like activated microglia in the hippocampus. TAg control animals maintained in the same diet regimen do not show rod-like microglia. D, b) The rod-like microglia in the NCCR animals become morphologically less pronounced in the hippocampus when they are put back on dox diet for 1 month. D, c) When the NCCR animals are always maintained on dox diet (SV40T is chronically turned off), the microglia display morphological features and distribution patterns typical of resting microglia that are similar to TAg control animals (TRE-SV40T) under different diet treatment conditions. E) Schematic showing the different diet treatments used in the experiment. Lower case letters next to the treatment conditions correspond to the lower case letters shown in the image panels in C and D. Scale bar = 100 μm.