Epidermal growth factor activates β-catenin via integrin-linked kinase to control proliferation of mesenchymal stromal cells.

Mesenchymal stromal cells (MSCs) are located in bone marrow where they help to maintain bone homeostasis and repair through the ability to expand in response to mitotic stimuli and differentiate into skeletal linages. The signalling mechanisms that enable precise control of MSC function remain unclear. Here, we have identified a non-canonical epidermal growth factor (EGF) signalling pathway in MSCs, which acts via integrin-linked kinase (ILK) to activate β-catenin, a key component of Wnt signalling. EGF induces nuclear translocation of β-catenin in MSCs but does not drive T cell factor (TCF)-mediated transactivation of Wnt target genes, and we demonstrate by Design of Experiments statistical analysis that the EGF/β-catenin and Wnt/β-catenin pathways do not cross-talk following co-stimulation with multiple concentrations of both ligands. By examining EGF-regulated genes in MSCs by RNA-Sequencing, we identified gene sets that were exclusively regulated by the EGF/b-catenin pathway, which were distinct from canonical EGF-regulated genes. In contrast, the expression of subsets of canonical EGF signalling gene targets were significantly influenced by b-catenin activation. These newly-identified EGF signalling pathways cooperate to enable EGF-mediated proliferation of MSCs by alleviating the suppression of cell cycle pathways induced by canonical EGF signalling. Examination of expression profiles of 3 samples of untreated MSCs, 3 samples EGF treated, 3 samples EGF + IWR-1 treated MSCs using RNA-seq analysis