Beta-cells and neural tissues share a gene activity program. Euclidean distances of genome-wide gene activity profiles, based on the presence or absence of mRNAs (A) or H3K4me3 (B) in each tissue. In both dendrograms, beta-cells are grouped with cerebral cortex and cerebellum. Similar conclusions were reached with principal component analysis using both purified beta-cells and islets (Supplemental Fig. S1).