School of Medicine

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  • Graham Walmsley

    Graham Walmsley

    MD Student, expected graduation Spring 2016


  • Mark Wossidlo

    Mark Wossidlo

    Postdoctoral Research fellow, Stem Cell Biology and Regenerative Medicine

    Current Research and Scholarly Interests I am interested in the epigenetic reprogramming of DNA methylation during early mammalian preimplantation development. Early mammalian development is characterized by dramatic epigenetic changes. Upon fertilization of the oocyte with the sperm, the maternal and paternal genomes of the zygote are extensively reprogrammed to ensure the development of a totipotent potential. During this period of epigenetic reprogramming, DNA methylation (5-methyl-cytosine, 5mC) of paternal and maternal chromosomes is erased and reset during formation of the blastocyst. Interestingly, in mouse zygotes, the paternal genome becomes actively demethylated, as judged by immunofluorescence with antibodies against 5mC and bisulfite-sequencing data. Since the discovery of active DNA demethylation many scientists were trying to identify the putative “DNA demethylase” and a lot of candidate enzymes and pathways have been suggested and disproven. The identification of the enzymatic conversion of 5mC to 5-hydroxymethyl-cytosine (5hmC), 5-formyl-cytosine (5fC) and 5-carboxyl-cytosine (5caC) by Tet1-3 enzymes sheds new light on this process.
    However, the analysis of epigenetic reprogramming in mammals is mainly focused on the mouse model and little is known about human embryonic development. Understanding the basic molecular mechanisms of human epigenetic reprogramming will impact human reproductive health and the generation of pluripotent stem cells