Peptide posttranslational modifications have been shown to regulate multiple aspects of cell signalling, thereby influencing cellular functions. The addition of O-linked Nacetylglucosamine to serine or threonine residues (O-GlcNAcylation) of proteins has only recently been characterized and its overall role in cell signalling remains elusive to date. Recent studies suggest an essential role of O-GlcNAcylation on the viability and pluripotency of mouse and human embryonic stem (ES) cells. Here we show that increased levels of O-GlcNAcylation in response to specific inhibition of O-GlcNAc hydrolase (Oga) hinder mouse ES cell differentiation. In addition to these findings, I could also demonstrate that increased O-GlcNAcylation leads to expression of a gene set normally epigenetically repressed in mouse ES cells and associated with a subpopulation resembling cells in the 2-cell-stage embryo. I also extended our lab's investigations to human induced pluripotent stem (iPS) cells. While mesendodermal differentiation remains unaffected by high O-GlcNAc levels, neural differentiation is severely disrupted in these cells. Human iPS cells with elevated O-GlcNAcylation are unable to commit to the ectodermal lineage and fail to organize in neural tube-like structures, so-called neural rosettes. Following these observations we performed mRNA sequencing analysis on human iPS cells with high O-GlcNAc levels and found gene expression to be significantly altered. Genes affected by increased O-GlcNAcylation include modulators of key neural developmental processes, for example components of the bone morphogenic protein signalling cascade.
|Date of Award||2016|
|Supervisor||Marios Stavridis (Supervisor)|