Fig. 2.

Studied opioid receptor mu-1 gene (OPRM1) CpGs and their association with prenatal exposure to maternal cigarette smoking (PEMCS). (Top) A total of 23 CpGs located within OPRM1 were considered, and their position and mean DNA methylation level (β, DNAm-β) across 132 investigated adolescents are shown. In addition, significant contributions (loading ≥ 0.30) of individuals’ CpGs to principal component 1 (PC1) and principle component 2 (PC2) are indicated by circles and squares, respectively. Arrows indicate excluded CpGs with abnormal distribution (see the Appendix, Fig. S1, available at jpn.ca). (Bottom) Associations between PEMCS and PC1 or PC2, with means ± standard errors of the mean adjusted for age, sex and perinatal variables (birth weight, adjusted for gestation duration, and breastfeeding duration) are shown. E = exon; TSS = transcription start site.