A Study of Allele-Specific Methylation on the Human X Chromosome

X chromosome inactivation in female mammals ensures dosage compensation between sexes. Allele-specific DNA methylation is a known epigenetic signature of X chromosome inactivation where the active and inactive X chromosomes are differentially methylated. Past studies on the link between allele-specific methylation and inactivation were biased to measuring methylation at CpG sites in promoter and genic regions. Our study uses a dataset of 95 methylomes sequenced via whole-genome bisulfite sequencing to analyze allele-specific methylation on the X chromosome at a single-base resolution. We examine sex-specific trends in DNA methylation on the XIST gene and find, consistent across the gene, hypomethylation in female samples relative to males. Our analysis of methylation at pseuoduatosomal regions in female samples reveals that PAR1 is hypermethylated and PAR2 is hypomethylated compared to the entire X chromosome. We also identify ASM-linked CpG sites and categorize them by functional region. A majority reside in non-coding regions, justifying further exploration into any influence that allele-specific methylation in non-coding regions has on gene expression.Undergraduat