Kristian Sumner

Dr. Tamara Davis

Biology Department

 

Gene Imprinting: Dynamic Methylation at Rasgrf1

 

Genomic imprinting is an epigenetic mechanism where a small number of genes are either expressed or silenced depending on which parent the allele was inherited from: either the maternal or paternal copy. One way of understanding how imprinting occurs is through studying differential distribution of DNA methylation and histone modification. These modifications help to distinguish between the maternal and paternal alleles form each other and regulate the expression of these copies. Studying how this is regulated is important because if it isn’t regulated properly there can be neurological/growth defects.

In mice, Rasgrf1 is an imprinted gene that is only paternally expressed, and functions in long-term memory formation. This gene has a differentially methylated region (DMR), which shows paternal allele-specific DNA methylation patterns. Recent research suggests that the Rasgrf1 DMR is more expansive than previously thought. The sites of methylation that occur in the expanded region, the uDMR, are still being investigated and aren’t as well defined as those in the original DMR. We are interested in understanding how and when these methylated regions change in size.

The purpose of this study is to explore the dynamic stage-specific methylation at Rasgrf1 by observing these patterns at different developmental stages in mice. We are analyzing the uDMR of Rasgrf1 in DNA isolated from sperm, 3.5, 6.5, and 14.5-day mouse embryos, as well as 5 day old and adult mouse tissue. The methylation pattern of Rasgrf1 is studied by using the chemical process of bisulfite mutagenesis. Bisulfite mutagenesis differentiates between unmethylated and methylated cytosines by converting unmethylated cytosines to uracil. Through DNA sequencing, sites that are methylated can be identified and analyzed to study the dynamic stage-specific changes in methylation within Rasgrf1. Through DNA analysis we can better understand how the uDMR of Rasgrf1 contracts and re-expands depending on the developmental stage of the mouse.