Mentor: Dr. Tamara Davis
Imprinted genes are genes whose expression is determined by parent of origin. Normally, each cell contains two alleles (different copies of a single gene), one from each parent, in which both are equally expressed. Conversely, imprinted genes only express one allele: either the paternal or maternal allele is expressed. This research aims to progress towards understanding the mechanism of this type of gene regulation. We believe that DNA methylation, (the addition of a methyl group (CH3) to a cytosine- one nucleotide base of DNA) is a key process in the regulation and expression of imprinted genes. Methylation frequently occurs at imprinted genes on CpG sites in gene promoters – a short span of nucleotide sequence that signals a starting point for transcription. As a result of methylation on CpG sites, the chemical structure of the DNA is altered which affects its ability to be expressed. This research aims to locate methylated CpG sites to better understand imprinted gene regulation.
Gtl2 is an imprinted gene located on chromosome 12, which we are currently studying in this research project. Its paternal copy is methylated and only its unmethylated maternal copy is expressed in mice. To date, two differentially methylated CpG sites have been identified. I am investigating the methylation pattern at another CpG site, located in exon 3 of the Gtl2 gene. The specific region e3 (exon three) is of particular interest because it is rich in CpG residues that signify many potentially methylated sites. In the lab we identify methylated cytosines by a process called bisulfite mutagenisis. As a result of this process all unmethylated cytosine nucleotides are replaced by a thymine; allowing us to identify methylation sites by searching for unchanged cytosine nucleotides in the e3 region of GtL2 gene. Knowing the methylated sites on the GtL2 gene, will brings us one step closer to understanding imprinted