Research Description:

Regulation of Imprinted Gene Expression on Mouse Chromosome 7C

In mammals, the majority of genes are equally expressed from both the maternally and paternally inherited chromosomes. However, there are a small number of genes in which only one parental allele, either maternal or paternal, is expressed while the other is silenced. These genes are known as imprinted genes. DNA sequence of these genes on the each allele is identical, so each cell must distinguish the parent-of-origin of individual allele via sequence independent molecular imprints. Differential DNA methylation has been implicated as a possible candidate for this molecular imprint, and it is thought to be established in the early stages of gametogenesis. During germ cell development, imprinted genes undergo an imprint switch to ensure that every germ cell contains only a "paternal" specific molecular imprint (spermatogenesis) or a "maternal" specific imprint (oogenesis). This resetting process is thought to consist of two stages-erasure and re-establishment. Erasure is the removal of existing parental-specific imprints from both alleles, and it is followed by a re-establishment of the correct epigenetic imprint. My working model is paternally expressed gene, Mkrn3, located on mouse chromosome 7c. This gene is unmethylated on the paternal, expressed allele and methylated on the maternal, silenced allele. The primary goal of my research is to establish at what stage of gametogenesis the methylation imprint switch occurs in Mkrn3. Initially, the high-resolution methylation pattern of the Mkrn3 promoter will be established in an allele specific manner for mouse brain and spleen, and then compared to the changes in DNA methylation during gametogenesis. The allele-specific methylation pattern will be obtained using high-resolution sodium bisulfite genomic sequencing.