Figure 3. (A) Heat maps represent DNA methylation of the CFTR promoter in normal fetal and adult tissues (1, first; 2, second; 3, third trimester of pregnancy). Rows represent individual samples and columns the percentage of DNA methylation measured by pyrosequencing in 6 CpG within the promoter of CFTR. (B) Boxplots show DNA methylation distribution in fetal and adult tissues. Asterisks indicate statistical significance in two-by-two comparisons (*P = 9 × 10−3; **P = 7.4 × 10−7, ***P = 1.2 × 10−12, “ns” is not significant (P = 0.75). (C) Boxplots represent inter-individual DNA methylation variations in blood (n = 12), lung (n = 6), nasal cell (n = 12) and colon (n = 16) samples. In two-by-two comparisons with colon samples, ns P = 0.547; *P = 0.011; **P = 2.04 10−7. The triangle at the bottom represents (from left to right) increasing levels of CFTR expression in the tissues.