Localized decrease of beta-catenin contributes to the differentiation of human embryonic stem cells.

Human embryonic stem cells (hESC) are pluripotent, and can be directed to differentiate into different cell types for therapeutic applications. To expand hESCs, it is desirable to maintain hESC growth without differentiation. As hESC colonies grow, differentiated cells are often found at the periphery of the colonies, but the underlying mechanism is not well understood. Here, we utilized micropatterning techniques to pattern circular islands or strips of matrix proteins, and examined the spatial pattern of hESC renewal and differentiation. We found that micropatterned matrix restricted hESC differentiation at colony periphery but allowed hESC growth into multiple layers in the central region, which decreased hESC proliferation and induced hESC differentiation. In undifferentiated hESCs, beta-catenin primarily localized at cell-cell junctions but not in the nucleus. The amount of beta-catenin in differentiating hESCs at the periphery of colonies or in multiple layers decreased significantly at cell-cell junctions. Consistently, knocking down beta-catenin decreased Oct-4 expression in hESCs. These results indicate that localized decrease of beta-catenin contributes to the spatial pattern of differentiation in hESC colonies.