Properties of heart enhancers. Heart enhancers include more specific enhancers (A) and enhancers adjacent to highly expressed genes (B). (A) The numbers in boxes represent the number of enhancers in a group. (B) The values of upper quartile, median, and lower quartile are indicated in each box, whereas the bars outside the box indicate semi-quartile ranges. Pairwise comparisons with significantly different expression levels of the adjacent gene are connected with gray lines (*0.01<P≦0.05 and ***P≦0.001 by (A) × 2 test or (B) Mann-Whitney U test). FB, forebrain; MB, midbrain; LB, limb; HT, heart.