development, including neuron differentiation (109/1201 genes in set, p=6.99×10−18), generation of neurons (114/1308, p=2.23×10−17), and axonogenesis (65/569 genes, p=1.73×10−15). We further found significant overlap of differentially methylated blocks with previously identified blocks associated with cancer (791 of the 896 blocks; 88.3%, odds ratio of enrichment: 1.56, χ2 p-value = 3.63×10−86), including skewed directionality – fetal samples in these blocks were almost exclusively hypomethylated compared to adult samples, which mirrored the hypomethylated blocks associated with cancer (82.3% of overlapping blocks). These results support the idea that these blocks may represent more general developmental and/or proliferative phenomena21 but also link these long-range changes in DNAm to mechanisms underlying human brain development.
