Epigenome analysis of buccal cells from monozygotic and dizygotic twins

Using the Infinium HM450 platform, we have performed a longitudinal study of DNA methylation at birth and age 18 months in DNA from buccal swabs from 10 monozygotic (MZ) and 5 dizygotic (DZ) twin pairs from the Peri/postnatal Epigenetic Twins Study (PETS) cohort. Beta methylation measurements from bisulphite-converted DNA and raw intensity values from 53 samples. Samples were collected at birth ('_B') or 18 months ('_18m'). Data were preprocessed using the Minfi package in R by the 'illumina' method and normalized to control probes. Subset quantile normalization was performed on type 1 and type 2 probes. Probes failing P detection cutoff of <0.01 were removed. Probes on the X and Y chromosomes have been removed from the processed data. Outlier samples were removed. Between-array quantile normalization was performed to arrive at the final data set of 330168 probes and 53 samples.