Fig. 5

Bisulfite pyrosequencing analysis of verification and validation set. Bisulfite pyrosequencing of 16 candidate CpG loci in atrial and ventricular cardiac tissue samples (detailed sample information, see Additional file 14: Table S1). The DNA methylation values (percentage) of three analysis sets are depicted: (1) initial discovery set (450K array analysis of atrial (n = 44, coloured dark blue) and ventricular (n = 5, coloured light blue) cardiac tissues from patients with CHDs), (2) verification set (atrial samples (n = 7, coloured dark red) and ventricular samples (n = 4, coloured orange) from the initially analysed sample cohort of the discovery set) and (3) validation set (four heart tissue samples (1x LA and 3x RA tissue) from adult patients with heart failure and 13 non-failing heart tissue samples (n = 4 atrial and n = 9 ventricular samples; coloured dark green and light green, respectively). All 16 candidate CpG loci show significant (p < 0.05) DNA methylation differences in atrial compared to ventricular cardiac tissue samples. Data is presented as standard box-and-whiskers plots (whiskers, 5th—95th percentile)