A Regulatory Network Involving beta-Catenin, E-Cadherin, PI3K/Akt, and Slug Balances Self-Renewal and Differentiation of Human Pluripotent Stem Cells in Response to Wnt Signaling

摘要

The mechanisms underlying disparate roles of the canonical Wnt signaling pathway in maintaining self-renewal or inducing differentiation and lineage specification in embryonic stem cells (ESCs) are not clear. In this study, we provide the first demonstration that self-renewal versus differentiation of human ESCs (hESCs) in response to Wnt signaling is predominantly determined by a two-layer regulatory circuit involving beta-catenin, E-cadherin, PI3K/Akt, and Slug in a time-dependent manner. Short-term upregulation of beta-catenin does not lead to the activation of T-cell factor (TCF)-eGFP Wnt reporter in hESCs. Instead, it enhances E-cadherin expression on the cell membrane, thereby enhancing hESC self-renewal through E-cadherin-associated PI3K/Akt signaling. Conversely, long-term Wnt activation or loss of E-cadherin intracellular beta-catenin binding domain induces TCF-eGFP activity and promotes hESC differentiation through beta-catenin-induced upregulation of Slug. Enhanced expression of Slug leads to a further reduction of E-cadherin that serves as a beta-catenin "sink" sequestering free cytoplasmic beta-catenin. The formation of such a framework reinforces hESCs to switch from a state of temporal self-renewal associated with short-term Wnt/beta-catenin activation to definitive differentiation.