In our study, maternal smoking, assessed objectively by cotinine, displayed a dose-dependent association with lower methylation of AHRR CpGs and higher methylation of CYP1A1 CpGs in cord blood.
In that paper, smoking-induced alteration of AHRR CpGs (including our top CpG) was seen in both B lymphoblastoid cells and in an independently collected sample of alveolar macrophage cells collected from bronchial lavage.
For our top CpG AHRR cg05575921, the percent difference in median methylation was 0.
But again, our top finding for AHRR cg05575921 due to maternal smoking was also reported in adult smokers in two different cell types--alveolar lung macrophage DNA and lymphoblast DNA (Monick et al.
We found 3 probes with SNPs within CpGs and removed them from the top 105 findings (rs77990586 in WBSCR17 cg20370581, rs115039881 in cg00531338 not specific to a gene, and rs6869832 in AHRR cg23576855).