A basic assumption about the normal nervous system is that its
neurons possess identical genomes. Here we present direct evidence
for genomic variability, manifested as chromosomal aneuploidy,
among developing and mature neurons. Analysis of mouse
embryonic cerebral cortical neuroblasts in situ detected lagging
chromosomes during mitosis, suggesting the normal generation of
aneuploidy in these somatic cells. Spectral karyotype analysis
identified33% of neuroblasts as aneuploid. Most cells lacked one
chromosome, whereas others showed hyperploidy, monosomy,
andor trisomy. The prevalence of aneuploidy was reduced by
culturing cortical explants in medium containing fibroblast growth
factor 2. Interphase fluorescence in situ hybridization on embryonic
cortical cells supported the rate of aneuploidy observed by
spectral karyotyping and detected aneuploidy in adult neurons.
Our results demonstrate that genomes of developing and adult
neurons can be different at the level of whole chromosomes.