RUI: Mechanisms that influence DNA methylation maintenance at imprinted genes in mouse

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The majority of genes in mammals are expressed from copies inherited from both parents, but a small number – called imprinted genes – are only expressed from one of the two copies. Normal patterns of mammalian growth and development are perturbed if the expression of imprinted genes is dysregulated. This research focuses on DNA methylation, which plays a leading role in directing differential expression of the mother’s vs. the father’s copy of imprinted genes. This project will examine the mechanisms responsible for maintenance of DNA methylation at imprinted genes, in order to better understand how distribution of this DNA modification on the two parental copies results in different expression patterns. These studies will be conducted at Bryn Mawr College, a women’s undergraduate institution, and will provide a diverse cohort of students the opportunity to advance scientific exploration, expand their data science literacy and prepare them to be the next generation of research scientists.While stable parental allele-specific differences in DNA methylation are inherited via gametes and modulate the expression of imprinted genes, less is known about the acquisition and maintenance of highly variable DNA methylation profiles at secondary differentially methylated regions (DMRs) that maintain imprinted expression patterns at individual loci. This research will provide insight into the mechanisms that govern establishment and maintenance of epigenetic profiles at secondary DMRs. An oxidative bisulfite approach will be used to examine 5- hydroxymethylcytosine (5hmC) content to test the hypothesis that hemimethylation at secondary DMRs is a consequence of 5hmC enrichment and leads to loss of methylation and pattern variability. Furthermore, the high level of hemimethylation observed at secondary DMRs suggests that maintenance of methylation at these sequences may be a complex process. The role of DNA methyltransferase 1 (Dnmt1) at secondary DMRs will be investigated by analysis of DNA methylation patterns in mice bearing a Dnmt1 mutation that has different effects at global genomic sequences vs. imprinted loci. The experiments will test the hypothesis that maintenance of methylation at secondary DMRs may depend on methylation at gametic DMRs and may require Dnmt3. The outcomes of this research will yield greater insights into the acquisition and maintenance of DNA methylation patterns critical for imprinted gene expression.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.