Table 1.

Probed CpGs within OPRM1

					PCA loading matrix‡
CpG no.	Illumina ID	DNAm-β	UCSC RefGene Group*	Modified position category†	PC1, 16.2%	PC2, 13.3%
1	cg12944573	0.56	TSS	Promoter	0.42§	0.52§
2	cg17256711	0.24	TSS	Promoter	0.32§	0.23
3	cg13245264	0.68	1st Exon (Exon 11)	Promoter	0.12	0.44§
4	cg10143581	0.88	TSS	Promoter	0.04	0.36§
5	cg22370006	0.15	TSS	Promoter	0.44§	−0.09
6	cg14262937	0.16	TSS	Promoter	0.41§	−0.11
7	cg06649410	0.19	1st Exon (Exon 1)	Promoter	—	—
8	cg05215925	0.13	1st Exon (Exon 1)	Promoter	0.74§	−0.22
9	cg12838303	0.13	1st Exon (Exon 1)	Promoter	0.74§	−0.21
10	cg22719623	0.44	1st Exon (Exon 1)	Promoter	0.70§	0.02
11	cg15085086	0.21	1st Exon (Exon 1)	Promoter	0.38§	−0.47
12	cg05017309	0.88	Body	Body	0.00	0.12
13	cg22366819	0.91	Body	Body	0.37§	0.50§
14	cg12466324	0.79	Body	Body	−0.61	0.45§
15	cg23384428	0.93	Body	Body	0.16	0.58§
16	cg11881038	0.78	Body	Body	—	—
17	cg04170440	0.85	Body	Body	0.20	0.59§
18	cg07813322	0.85	3’UTR	Body	−0.31	0.13
19	cg15658985	0.86	Body	Body	−0.08	−0.52
20	cg26415516	0.78	3’UTR	Body	−0.27	0.08
21	cg27296341	0.68	Body	Body	0.44§	0.09
22	cg10276116	0.92	Body	Body	−0.01	0.47§
23	cg07356123	0.87	Body	Body	0.21	0.38§

DNAm-β = DNA methylation β; OPRM1 = opioid receptor mu-1 gene; PC = principal component; PCA = principal component analysis; TSS = transcription start site; UTR = untranslated region; UCSC = University of California, Santa Cruz.

^*Annotations according to the UCSC database (http://genome.ucsc.edu/)

^†Modified position categorizations, as adopted from Sandoval and colleagues.⁴¹

^‡Percentages represent the proportion of variance among CpG DNA methylation explained by the principal component.

^§Positive PC loading ≥ 0.30, as suggested previously for data with sample sizes ≥ 100.⁴⁵