To determine the influence of both methylation and CNAs on allelic expression, we genotyped highly informative exonic SNPs within NAPL1L5, PEG10, H19, IGF2, MEST, KCNQ1OT1, MEG3, PEG3, L3MBTL1 and NHP2L1 in 57 cancer cell lines with allelic expression determined by PCR with reverse transcription (RT-PCR) in heterozygous cases (Supplementary Figs 10–19). The gene discussed is PEG3; the disease is cancer.