A tale of signalling and chromatin – how GSK3/WNT pathway controls cell fate decision through CHD4 regulation in stem cells
Abstract
Despite the known importance of WNT signalling in mammalian development and various cancers, its downstream mechanistic effect on chromatin regulation remains less understood. When WNT signalling is activated, Glycogen Synthase Kinase 3 (GSK3) is inhibited, leading to dephosphorylation and nuclear accumulation of β-catenin, where it regulates WNT-target genes. However, GSK3 is a major kinase with multiple client proteins, and how phosphorylation of additional chromatin proteins downstream of GSK3 regulates stem cell identity remains poorly understood. Using phospho-proteomic approaches we found that CHD4, a chromatin repressor important in lineage differentiation, is de-phosphorylated downstream of WNT-signalling in mouse embryonic stem cells (mESCs). To unravel the overall CHD4 function, we generated Chd4-knockout mESCs and observed profound upregulation of primitive endoderm markers, implying a repressive role of CHD4 for endoderm lineage specification. To address how differential phosphorylation of CHD4 downstream of WNT signalling is involved in chromatin and stem cell biology, we used gene editing and engineered mESCs expressing different CHD4 phospho-variants. Our findings connect WNT signalling and CHD4, two key players with opposite functions in stem cell biology, providing key insights into how signal transduction cascades control chromatin functions and cell fate decisions in stem cells. Thesis is embargoed until 31 July 2028.
