CpH sites were an important source of the hemispheric differences in DNA methylation (5465 CpHs, 0.82% ± 0.02% change in PD; 742 CpGs, 4.40% ± 0.14% change in PD; p < 10− 25 for CpH enrichment, hypergeometric test; Fig. 2c; Additional file 1: Figure S3). Here, CPE is linked to Parkinson disease.