The widespread methylome changes that occur across brain development - ranging from early fetal life23, the transition into postnatal life shown here, and through adulthood24 – appear to track first the loss of immature neurons prior to birth followed by the rise of non-neuronal cell types in postnatal life through adulthood (see Figure 2). While the quantitative estimates of cell composition employed here utilized a series of cell types that combined epigenetic data from adult human tissue and derived cellular systems, the proportion of pluripotent-like cells are quite consistent across two independent datasets and brain regions, with ~15% of the cells manifesting this signature by 14 post-conception weeks (Figures 2A,F), and may relate to recent classifications of replicating versus quiescent fetal neurons using single cell analysis37.
