Figure 2.

Identification of cell types targeted by aneuploidy in the old cortex. (A) Flow cytometric analysis of cortical nuclei with anti-NeuN antibody, detected with Alexa-488 secondary antibody. Isotype control and anti-NeuN specific staining on old cortex are shown. Isolated mouse cortical nuclei were gated based on forward scatter and side scatter (data not shown) and gated into NeuN+ DAPI+ and NeuN− DAPI+ populations. The gates were set based on the IgG1 isotype control. (B) Levels of aneuploidy obtained by interphase FISH analysis of chromosomes 1 and 18 performed on FACS enriched cortical neuronal and non- neuronal nuclei in 28-month-old mice. Chromosome 18 shows a statistically significantly higher level of aneuploidy than chromosome 1 in NeuN− cells (dark gray *P < 0.0001). (C) To avoid interference of the locus specific probe with the green fluorescence arising from NeuN staining (Alexa 488), the same BAC probe previously used has been labeled with spectrum Aqua. We chose yellow as pseudo-color to display the spectrum Aqua dye. Examples of NeuN- cortical nuclei aneuploid for chromosomes 1 and 18 performed with our two-color FISH approach are shown. The left panel shows a nucleus that carries three copies of chromosome 1, visualized by three red and three yellow signals (gain). The right panel shows that a nucleus carries one copy of chromosome 18, visualized by one red and one yellow signal (loss).